3.7.3 Fan Systems

Baseline Building Fan System Summary

The baseline building fan system is summarized in this section. See [bookref id="hvac-mapping"] for the HVAC baseline building system mapping.

Total baseline building fan system power for the baseline building fan systems is given in [bookref id="baseline-building-fan-system-–-ASHRAE-standard-90.1-2007"] for ASHRAE Standard 90.1-2007 and [bookref id="baseline-building-fan-system-–-ASHRAE-standard-90.1-2001"] for ASHRAE Standard 90.1-2001. In these tables, "cfms" is the supply fan air flow at peak design conditions. This is calculated for the baseline building with the sizing procedure described in [bookref id="calculation-process-for-tax-deductions-and-green-building-ratings"] and [bookref id="procedure-for-adjusting-equipment-hvac-sizes-in-the-baseline-building"]. This brake horsepower includes the supply fan, the return fan, and exhaust fans. Exhaust fans include kitchen hoods, toilets, fume hoods, and other miscellaneous fans that operate at design conditions.

[table title="Baseline Building Fan System – ASHRAE Standard 90.1-2007" id="baseline-building-fan-system-–-ASHRAE-standard-90.1-2007"]

	System Types 1-2	System Types 3-4	System Types 5-8
Brake Horsepower (bhp)	Not applicable	0.00094 x cfm_s + A	0.0013 x cfm_s + A
Fan Motor Efficiency (hm)	Not applicable	ASHRAE Standard 90.1-2007, Table 10.8	ASHRAE Standard 90.1-2007, Table 10.8
Fan Power (W)	0.3 x cfm_s	(bhp x 746)/_$\eta$m	(bhp x 746)/_$\eta$m
The term “A” for system types 3-8, is calculated based on equipment in the proposed design using the procedure in Table 6.5.3.1.1B of ASHRAE Standard 90.1-2007. This accounts for various additional fan pressure drops associated with special conditions.

[table title="Baseline Building Fan System – ASHRAE Standard 90.1-2001" id="baseline-building-fan-system-–-ASHRAE-standard-90.1-2001"]

	Fan Size	System Types 1-4	System Types 5-8
Nameplate Horsepower (nhp)	< 20,000 cfm	0.0012 x cfms + P_filter + P_process + P_relief	0.0017 x cfm_s + P_filter + P_process + P_relief
	=> 20,000 cfm	0.0011 x cfm_s + P_filter + P_process + P_relief	0.0015 x cfm_s + P_filter+ P_process + P_relief
Fan Motor Efficiency (hm)		ASHRAE Standard 90.1-2001, Table 10.2	ASHRAE Standard 90.1-2001, Table 10.2
Brake Horsepower (bhp)		nhp x _$\eta$m	nhp x _$\eta$m
Fan Power (W)		(bhp x 746)/ _$\eta$m	(bhp x 746)/ _$\eta$m
The terms Pfilter, Pprocess, and Prelief account for additional pressure drop. These are based on features in the proposed design such as special filtration, process fans, and relief or return fans. See Section 6.3.3.1 of ASHRAE Standard 90.1-2001 and the associated User's Manual for details on how to calculate these adders.

When the proposed design has exhaust fans (toilets or kitchens), return fans, or fume hood exhaust systems, the baseline building has the same systems. The brake horsepower determined from [bookref id="baseline-building-fan-system-–-ASHRAE-standard-90.1-2007"] and [bookref id="baseline-building-fan-system-–-ASHRAE-standard-90.1-2001"] is allocated to these baseline building fan systems proportionally to the allocation in the proposed design. The allocation of brake horsepower to the supply fan, the return and any exhaust or fume hood fans is based on the ratios described below.

Supply Fan Ratio
Applicability	Systems that serve thermal blocks that have exhaust, fume hoods, kitchen exhaust or return fans
Definition	The ratio of supply fan brake horsepower in the proposed design to total fan system brake horsepower for the proposed design at design conditions
Units	Unitless ratio
Input Restrictions	Derived from other building descriptors
Baseline Rules	Same as proposed design

Return Fan Ratio
Applicability	Systems that serve thermal blocks that have exhaust, fume hoods, kitchen exhaust or return fans
Definition	The ratio of return fan brake horsepower in the proposed design to total fan system brake horsepower for the proposed design at design conditions
Units	Unitless ratio
Input Restrictions	Derived from other building descriptors
Baseline Rules	Same as proposed design

Exhaust Fan Ratio
Applicability	Systems that serve thermal blocks that have exhaust, fume hoods, kitchen exhaust or return fans
Definition	The ratio of exhaust fan brake horsepower in the proposed design to total fan system brake hp for the proposed design at design conditions. Exhaust fans include toilet exhaust, kitchen hoods and other miscellaneous exhaust. Fume hood exhaust is treated separately.
Units	Unitless ratio
Input Restrictions	Derived from other building descriptors. In the event that a common exhaust system serves thermal blocks that are served by different HVAC systems, the brake horsepower shall be divided in proportion to design cfm.
Baseline Rules	Same as proposed design

Supply Fans

Fan System Modeling Method
Applicability	All fan systems
Definition	Software commonly models fans in three ways. Power-per-unit-flow. The simple method is for the user to enter the electric power per unit of flow (W/cfm). This method is commonly used for unitary equipment and other small fan systems. Static pressure. A more detailed method is to model the fan as a system whereby the static pressure, fan efficiency, part-load curve, and motor efficiency are specified at design conditions. Break horsepower. A third method is to specify brake horsepower at design conditions instead of fan efficiency and static pressure. This is a variation of the second method whereby brake horsepower is specified in lieu of static pressure and fan efficiency. The latter two methods are commonly used for VAV and other larger fan systems.
Units	List: power-per-unit-flow, static pressure or brake horsepower
Input Restrictions	As designed. The power-per-unit-flow method shall be used when no fan performance data is available for the proposed design cooling system, e.g. only EER or SEER are available.
Baseline Rules	If the proposed design uses the power-per-unit-flow method, the baseline building shall also use this method, otherwise the baseline building shall use the brake horsepower method.

Supply Fan Design Air Rated Capacity
Applicability	All fan systems
Definition	The design air flow rate of the supply fan(s) at design conditions. This building descriptor sets the 100% point for the fan part-load curve.
Units	cfm
Input Restrictions	As designed. This input should be at least as great as the sum of the design air flow specified for each of the thermal blocks that are served by the fan system. For multiple deck systems, a separate entry should be made for each deck.
Baseline Rules	The program shall automatically size the air flow at each thermal block to meet the loads. The design air flow rate calculation shall be based on a 20 degree temperature differential between supply air and the room air. The supply fan design air flow rate shall be the sum of the calculated design air flow for the thermal blocks served by the fan system.

Fan Control Method
Applicability	All fan systems
Definition	A description of how the supply (and return/relief) fan(s) are controlled. The options include: Constant volume Variable-flow, inlet or discharge dampers Variable-flow, inlet guide vanes Variable-flow, variable speed drive (VSD) Variable-flow, variable pitch blades Variable-flow, other Two-speed Constant volume, cycling (fan cycles with heating and cooling)
Units	List (see above)
Input Restrictions	As designed
Baseline Rules	Applicable to variable air volume systems Based on the prescribed system type. Refer to the HVAC System Map in [bookref id="hvac-mapping"].

[table title="Baseline Building Fan Control Method" id="baseline -bilding-fan-control-method"]

Baseline building System	Fan Control Method
System 1 – PTAC	Constant volume
System 2 – PTHP	Constant volume
System 3 – PSZ-AC	Constant volume
System 4 – PSZ-HP	Constant volume
System 5 – Packaged VAV with Reheat	Variable-flow, variable speed drive (VSD)
System 6 – Packaged VAV with PFP boxes	Variable-flow, variable speed drive (VSD)
System 7 – VAV with Reheat	Variable-flow, variable speed drive (VSD)
System 8 – VAV with PFP boxes	Variable-flow, variable speed drive (VSD)

Supply Fan Brake Horsepower
Applicability	All fan systems, except those specified using the power-per-unit-flow method
Definition	The design shaft brake horsepower of the supply fan(s). This input does not need to be supplied if the Supply Fan kW is supplied.
Units	Horsepower (hp)
Input Restrictions	As designed. If this building descriptor is specified for the proposed design, then the Static Pressure and Fan Efficiency are not.
Baseline Rules	See [bookref id="baseline-building-fan-system-–-ASHRAE-standard-90.1-2007"] for ASHRAE Standard 90.1-2007 and [bookref id="baseline-building-fan-system-–-ASHRAE-standard-90.1-2001"] for ASHRAE Standard 90.1-2001. These tables give the baseline building fan system brake horsepower. The brake horsepower for the supply fan is this value times the Supply Fan Ratio (see above).

Supply Fan Static Pressure
Applicability	All fan systems, except those specified using the power-per-unit-flow method
Definition	The design static pressure for the supply fan. This is important for both fan electric energy usage and duct heat gain calculations.
Units	Inches of water column (in. H₂0)
Input Restrictions	As designed. The design static pressure for the supply fan does not need to be specified if the supply fan brake horsepower (bhp) is specified.
Baseline Rules	Not applicable. When Static Pressure and Fan Efficiency are entered for the proposed design, the baseline building shall use Brake Horsepower.

Supply Fan Efficiency
Applicability	All fan systems, except those specified using the power-per-unit-flow method
Definition	The efficiency of the fan at design conditions
Units	Unitless
Input Restrictions	As designed. The supply fan efficiency does not need to be specified if the supply fan brake horsepower (bhp) is specified.
Baseline Rules	Not applicable. When Static Pressure and Fan Efficiency are entered for the proposed design, the baseline building shall use Brake Horsepower.

Supply Motor Efficiency
Applicability	All supply fans, except those specified using the power-per-unit-flow method
Definition	The full-load efficiency of the motor serving the supply fan
Units	Unitless
Input Restrictions	As designed. Not applicable when the power-per-unit-flow method is used.
Baseline Rules	From Table 10.8 of ASHRAE Standard 90.1-2007 or Table 10.2 of ASHRAE Standard 90.1-2001

Fan Position
Applicability	All supply fans
Definition	The position of the supply fan relative to the cooling coil. The configuration is either draw through (fan is downstream of the coil) or blow through (fan is upstream of the coil).
Units	List (see above)
Input Restrictions	As designed.
Baseline Rules	Draw through

Motor Position
Applicability	All supply fans
Definition	The position of the supply fan motor relative to the cooling air stream. The choices are: in the air stream or out of the air stream.
Units	List (see above)
Input Restrictions	As designed.
Baseline Rules	In the air stream

Fan Part-Flow Power Curve

Applicability

All variable flow fan systems

Definition

A part-load power curve which represents the percentage full-load power draw of the supply fan as a function of the percentage full-load air flow. The curve is typically represented as a quadratic equation with an absolute minimum power draw specified.

Units

Unitless ratio

Input Restrictions

As designed. The default fan curve shall be selected from Equation (6.7.3-1) and [bookref id="fan-curve-default-values"] for the type of fan specified in the proposed design.

(6.7.3-1)

$Greater \;of$

$PLR = a + b \cdot FanRatio + c \cdot FanRatio^2 + d \cdot FanRatio^3$

$PLR = PowerMin $

where

PLR	Ratio of fan power at part load conditions to full load fan power
PowerMin	Minimum fan power
FanRatio	Ratio of cfm at part-load to full-load cfm
a, b, c and d	Constants from [bookref id="fan-curve-default-values"] below

[table title="Fan Curve Default Values" id="fan-curve-default-values"]

Fan Type - Control Type	a	b	c	d	%Power_Min
AF or BI riding the curve^a	0.1631	1.5901	-0.8817	0.1281	70%
AF or BI with inlet vanes^a	0.9977	-0.659	0.9547	-0.2936	50%
FC riding the curve^a	0.1224	0.612	0.5983	-0.3334	30%
FC with inlet vanes^a	0.3038	-0.7608	2.2729	-0.8169	30%
Vane-axial with variable pitch blades^a	0.1639	-0.4016	1.9909	-0.7541	20%
Any fan with VSD (use for baseline building)^b	0.0013	0.1470	0.9506	-0.0998	20%
VSD with static pressure reset^c	-0.0031	0.0991	1.0268	-0.1128	20%
Data Sources: a. ECB Compliance Supplement, public review draft, Version 1.2, March 1996, but adjusted to be relatively consistent with the curve specified in the PRM. b. The fan curve for VSD is specified in Table G3.1.3.15 c. Advanced VAV System Design Guide, California Energy Commission, CEC Publication 500,-03-082 A-11, April 2005, but adjusted to be relatively consistent with the curve specified in the PRM..

Baseline Rules

Not applicable for baseline building systems 1-4. The curve for VSD fans shall be used for baseline building systems 5-8 with no adjustment for static pressure setpoint reset.

Supply Fan kW

Applicability

Fan systems that use the power-per-unit-flow method

Definition

The supply fan power per unit of flow.

Units

kW/cfm

Input Restrictions

As designed or specified in the manufacturers’ literature. For units with rated total cooling capacities less than 120,000 Btu/h, the user may default to a value calculated as follows:

(6.7.3-2)

$$ Fan_{kw} = 0.365 \times \frac{Q_{rated}}{30,000} $$

where

Fan_kw	The supply fan power (kW)
Q_rated	The rated total cooling capacity (Btu/h)

Baseline Rules

Applicable when the baseline building uses the power-per-unit-flow method. Fan power is determined using [bookref id="baseline-building-fan-system-–-ASHRAE-standard-90.1-2007"] for ASHRAE Standard 90.1-2007 and [bookref id="baseline-building-fan-system-–-ASHRAE-standard-90.1-2001"] for ASHRAE Standard 90.1-2001. This power is then multiplied by the supply fan ratio.

Relief Fans

The baseline building has a return fan when the baseline building system is type 3 through 8 and the proposed design has a return fan.

Plenum Zone
Applicability	Any system with return ducts or return air plenum
Definition	A reference to the thermal block that serves as return plenum or where the return ducts are located
Units	Text, unique
Input Restrictions	As designed
Baseline Rules	Applicable when the baseline building has a return fan. Same as the proposed design when the proposed design has a plenum, otherwise, the return air ducts are assumed to be located in the space.

Return Air Path
Applicability	Any system with return ducts or return air plenum
Definition	Describes the return path for air. This can be one of the following: ducted return; plenum return; or direct-to-unit.
Units	List (see above)
Input Restrictions	As designed
Baseline Rules	Applicable when the baseline building has a return fan. For baseline building systems 1 and 2, the return air path shall be direct-to-unit. For baseline building systems 3 through 8 and when the proposed design is direct-to-unit, the baseline building shall be ducted return, otherwise the baseline building return air path shall be same as proposed design.

Return/Relief Air Rated Capacity
Applicability	All systems with a return or relief fan
Definition	The design air flow fan capacity of the return or relief fan(s). This sets the 100% fan flow point for the part-load curve (see below).
Units	cfm
Input Restrictions	As designed
Baseline Rules	Applicable when the baseline building has a return fan. The return fan air Rated Capacity shall be equal to the baseline building supply fan capacity less exhaust air flow.

Return/Relief Fan Brake Horsepower
Applicability	Any system with return or relief fans that uses the brake horsepower method
Definition	The design shaft brake horsepower of the return/relief fan(s)
Units	Brake horsepower (bhp)
Input Restrictions	As designed
Baseline Rules	Applicable when the baseline building has a return fan. The bhp of the return fan shall be the fan system brake horsepower (see [bookref id="baseline-building-fan-system-–-ASHRAE-standard-90.1-2007"] and [bookref id="baseline-building-fan-system-–-ASHRAE-standard-90.1-2001"]) times the return fan ratio. In other words, brake horsepower is allocated in proportion to the proposed design.

Return/Relief Design Static Pressure
Applicability	Any system with return or relief fans that uses the static pressure method
Definition	The design static pressure for return fan system. This is important for both fan electric energy usage and duct heat gain calculations.
Units	Inches of water column (in. H₂0)
Input Restrictions	As designed. The design static pressure for the return fan does not need to be specified if the return fan brake horsepower (bhp) is specified.
Baseline Rules	Not applicable. When Static Pressure and Fan Efficiency are entered for the proposed design, the baseline building shall use Brake Horsepower.

Return/Relief Fan Efficiency
Applicability	Any system with return or relief fans that uses the static pressure method
Definition	The efficiency of the fan at design conditions
Units	Unitless
Input Restrictions	As designed. The return/relief fan efficiency does not need to be specified if the return fan brake horsepower (bhp) is specified.
Baseline Rules	Not applicable. When Static Pressure and Fan Efficiency are entered for the proposed design, the baseline building shall use Brake Horsepower.

Return/Relief Motor Efficiency
Applicability	All return fans, except those specified using the power-per-unit-flow method
Definition	The full-load efficiency of the motor serving the supply fan
Units	Unitless
Input Restrictions	As designed. Not applicable when the power-per-unit-flow method is used.
Baseline Rules	From Table 10.8 of ASHRAE Standard 90.1-2007 or Table 10.2 of ASHRAE Standard 90.1-2001

Motor Position
Applicability	All return fans
Definition	The position of the supply fan motor relative to the cooling air stream. The choices are: in the air stream or out of the air stream.
Units	List (see above)
Input Restrictions	As designed.
Baseline Rules	In the air stream

Fan Part-Flow Power Curve
Applicability	All return fans for variable flow fan systems.
Definition	A part-load power curve which represents the percentage full-load power draw of the supply fan as a function of the percentage full-load air flow.
Units	Unitless ratio
Input Restrictions	As designed. The default fan curve shall be selected from Equation (6.7.3-1) and [bookref id="fan-curve-default-values"] for the type of fan specified in the proposed design.
Baseline Rules	Not applicable for baseline building systems 1-4. The curve for VSD fans shall be used for baseline building systems 5-8 that have a return/relief fan.

Return/Relief Fan kW
Applicability	Any system with a return fan
Definition	The supply fan power per unit of flow
Units	kW/cfm
Input Restrictions	As specified in the manufacturers’ literature
Baseline Rules	Applicable when the baseline building uses the power-per-unit-flow method. Fan power is determined using [bookref id="baseline-building-fan-system-–-ASHRAE-standard-90.1-2007"] for ASHRAE Standard 90.1-2007 and [bookref id="baseline-building-fan-system-–-ASHRAE-standard-90.1-2001"] for ASHRAE Standard 90.1-2001. This power is then multiplied by the return fan ratio.

Exhaust Fan Systems

Exhaust fans include toilet exhaust, kitchen exhaust, as well as fume hoods in laboratories and other spaces. Some systems typically operate at constant flow, while flow varies for other systems depending on, for instance, the position of the sash for fume hoods. Exhaust fan flow is specified and scheduled for each thermal block. An exhaust fan system may serve multiple thermal blocks. The baseline building has exhaust fans when the proposed design has exhaust fans. The exhaust air flow is the same for the baseline building and the proposed design.

Exhaust Fan Name
Applicability	All exhaust systems serving multiple thermal blocks
Definition	A unique descriptor for each exhaust fan. This should be keyed to the construction documents, if possible, to facilitate plan checking. Exhaust rates and schedules at the thermal block level refer to this name.
Units	Text, unique
Input Restrictions	Where applicable, this should match the tags that are used on the plans.
Baseline Rules	The baseline building will have an exhaust system that corresponds to the proposed design. The name can be identical to that used for the proposed design or some other appropriate name may be used.

Exhaust Fan System Modeling Method
Applicability	All exhaust fan systems
Definition	Software commonly models fans in three ways. See definition for supply system modeling method.
Units	List: power-per-unit-flow, static pressure or brake horsepower
Input Restrictions	As designed
Baseline Rules	If the proposed design uses the power-per-unit-flow method, the baseline building shall also use this method, otherwise the baseline building shall use the brake horsepower method.

Exhaust Fan Rated Capacity
Applicability	All exhaust systems
Definition	The rated design air flow rate of the exhaust fan system. This building descriptor defines the 100% flow case for the part-flow curve. Actual air flow is the sum of the flow specified for each thermal block, as modified by the schedule for each thermal block.
Units	cfm
Input Restrictions	As designed
Baseline Rules	Same as proposed design

Fan Control Method
Applicability	All exhaust fan systems
Definition	A description of how the exhaust fan(s) are controlled. The options include: Constant volume Two-speed Variable-flow, inlet or discharge dampers Variable-flow, inlet guide vanes Variable-flow, variable speed drive (VSD) Variable-flow, variable pitch blades
Units	List (see above)
Input Restrictions	As designed, however, when exhaust fan flow at the thermal block level is varied through a schedule, one of the variable-flow options shall be specified.
Baseline Rules	The baseline building exhaust fan control shall generally be the same as the proposed design. For laboratories that have exhaust flow of 5,000 cfm or more, the baseline building exhaust flow shall vary in response to scheduled fume hood exhaust and lab zone airflow schedules. Fume hood exhaust flow control shall be the same as design, and general exhaust (relief) shall be VSD.

Exhaust Fan Schedule
Applicability	All exhaust fan systems
Definition	A schedule that indicates when the exhaust fan system is available for operation. Exhaust fan flow is specified at the thermal block level.
Units	Data structure: schedule, on/off
Input Restrictions	The exhaust fan system shall be available during all periods when one or more thermal blocks served by the system are scheduling exhaust.
Baseline Rules	Same as the proposed design

Exhaust Fan Brake Horsepower
Applicability	All exhaust fan systems
Definition	The design shaft brake horsepower of the exhaust fan(s).
Units	Brake horsepower (bhp)
Input Restrictions	As designed
Baseline Rules	The bhp for the baseline building is the total system fan horsepower from [bookref id="baseline-building-fan-system-–-ASHRAE-standard-90.1-2007"] or [bookref id="baseline-building-fan-system-–-ASHRAE-standard-90.1-2001"] times the exhaust fan ratio.

Exhaust Fan Design Static Pressure
Applicability	Any system with return or relief fans that uses the static pressure method
Definition	The design static pressure for exhaust fan system. This is important for both fan electric energy usage and duct heat gain calculations.
Units	Inches of water column (in. H₂0)
Input Restrictions	As designed. The design static pressure for the exhaust fan does not need to be specified if the exhaust fan brake horsepower (bhp) is specified.
Baseline Rules	Not applicable. When static pressure and fan efficiency are entered for the proposed design, the baseline building shall use brake horsepower.

Exhaust Fan Efficiency
Applicability	Any exhaust fan system that uses the static pressure method
Definition	The efficiency of the exhaust fan at rated capacity
Units	Unitless
Input Restrictions	As designed. The exhaust fan efficiency does not need to be specified if the return fan brake horsepower (bhp) is specified.
Baseline Rules	Not applicable. When static pressure and fan efficiency are entered for the proposed design, the baseline building shall use brake horsepower.

Exhaust Fan Motor Efficiency
Applicability	All exhaust fan systems
Definition	The full-load efficiency of the motor serving the exhaust fan
Units	Unitless
Input Restrictions	As designed
Baseline Rules	From Table 10.8 of ASHRAE Standard 90.1-2007 or Table 10.2 of ASHRAE Standard 90.1-2001

Fan Part-Flow Power Curve
Applicability	All variable flow exhaust fan systems
Definition	A part-load power curve which represents the ratio full-load power draw of the exhaust fan as a function of the ratio full-load air flow.
Units	Unitless ratio
Input Restrictions	As designed. The default fan curve shall be selected from Equation (6.7.3-1) and [bookref id="fan-curve-default-values"] for the type of fan specified in the proposed design.
Baseline Rules	The baseline building fan curve shall be selected from Equation (6.7.3-1) and [bookref id="fan-curve-default-values"] for the type of fan specified in the proposed design.

Exhaust Fan KW
Applicability	All exhaust systems
Definition	The fan power of the exhaust fan per unit of flow. This building descriptor is applicable only with the power-per-unit-flow method.
Units	W/cfm
Input Restrictions	As designed.
Baseline Rules	The fan system power from [bookref id="baseline-building-fan-system-–-ASHRAE-standard-90.1-2007"] or [bookref id="baseline-building-fan-system-–-ASHRAE-standard-90.1-2001"]

90.1-2007

Baseline Building Fan System Summary

The baseline building fan system is summarized in this section. See [bookref id="hvac-mapping"] for the HVAC baseline building system mapping.

Total baseline building fan system power for the baseline building fan systems is given in [bookref id="baseline-building-fan-system-–-ASHRAE-standard-90.1-2007"]. In this table, "cfms" is the supply fan air flow at peak design conditions. This is calculated for the baseline building with the sizing procedure described in [bookref id="calculation-process-for-tax-deductions-and-green-building-ratings"] and [bookref id="procedure-for-adjusting-equipment-hvac-sizes-in-the-baseline-building"]. This brake horsepower includes the supply fan, the return fan, and exhaust fans. Exhaust fans include kitchen hoods, toilets, fume hoods, and other miscellaneous fans that operate at design conditions.

[table title="Baseline Building Fan System – ASHRAE Standard 90.1-2007" id="baseline-building-fan-system-–-ASHRAE-standard-90.1-2007"]

	System Types 1-2	System Types 3-4	System Types 5-8
Brake Horsepower (bhp)	Not applicable	0.00094 x cfm_s + A	0.0013 x cfm_s + A
Fan Motor Efficiency (hm)	Not applicable	ASHRAE Standard 90.1-2007, Table 10.8	ASHRAE Standard 90.1-2007, Table 10.8
Fan Power (W)	0.3 x cfm_s	(bhp x 746)/_$\eta$m	(bhp x 746)/_$\eta$m
The term “A” for system types 3-8, is calculated based on equipment in the proposed design using the procedure in Table 6.5.3.1.1B of ASHRAE Standard 90.1-2007. This accounts for various additional fan pressure drops associated with special conditions.

When the proposed design has exhaust fans (toilets or kitchens), return fans, or fume hood exhaust systems, the baseline building has the same systems. The brake horsepower determined from [bookref id="baseline-building-fan-system-–-ASHRAE-standard-90.1-2007"] is allocated to these baseline building fan systems proportionally to the allocation in the proposed design. The allocation of brake horsepower to the supply fan, the return and any exhaust or fume hood fans is based on the ratios described below.

Supply Fan Ratio
Applicability	Systems that serve thermal blocks that have exhaust, fume hoods, kitchen exhaust or return fans
Definition	The ratio of supply fan brake horsepower in the proposed design to total fan system brake horsepower for the proposed design at design conditions
Units	Unitless ratio
Input Restrictions	Derived from other building descriptors
Baseline Rules	Same as proposed design

Return Fan Ratio
Applicability	Systems that serve thermal blocks that have exhaust, fume hoods, kitchen exhaust or return fans
Definition	The ratio of return fan brake horsepower in the proposed design to total fan system brake horsepower for the proposed design at design conditions
Units	Unitless ratio
Input Restrictions	Derived from other building descriptors
Baseline Rules	Same as proposed design

Exhaust Fan Ratio
Applicability	Systems that serve thermal blocks that have exhaust, fume hoods, kitchen exhaust or return fans
Definition	The ratio of exhaust fan brake horsepower in the proposed design to total fan system brake hp for the proposed design at design conditions. Exhaust fans include toilet exhaust, kitchen hoods and other miscellaneous exhaust. Fume hood exhaust is treated separately.
Units	Unitless ratio
Input Restrictions	Derived from other building descriptors. In the event that a common exhaust system serves thermal blocks that are served by different HVAC systems, the brake horsepower shall be divided in proportion to design cfm.
Baseline Rules	Same as proposed design

Supply Fans

Fan System Modeling Method
Applicability	All fan systems
Definition	Software commonly models fans in three ways. Power-per-unit-flow. The simple method is for the user to enter the electric power per unit of flow (W/cfm). This method is commonly used for unitary equipment and other small fan systems. Static pressure. A more detailed method is to model the fan as a system whereby the static pressure, fan efficiency, part-load curve, and motor efficiency are specified at design conditions. Break horsepower. A third method is to specify brake horsepower at design conditions instead of fan efficiency and static pressure. This is a variation of the second method whereby brake horsepower is specified in lieu of static pressure and fan efficiency. The latter two methods are commonly used for VAV and other larger fan systems.
Units	List: power-per-unit-flow, static pressure or brake horsepower
Input Restrictions	As designed. The power-per-unit-flow method shall be used when no fan performance data is available for the proposed design cooling system, e.g. only EER or SEER are available.
Baseline Rules	If the proposed design uses the power-per-unit-flow method, the baseline building shall also use this method, otherwise the baseline building shall use the brake horsepower method.

Supply Fan Design Air Rated Capacity
Applicability	All fan systems
Definition	The design air flow rate of the supply fan(s) at design conditions. This building descriptor sets the 100% point for the fan part-load curve.
Units	cfm
Input Restrictions	As designed. This input should be at least as great as the sum of the design air flow specified for each of the thermal blocks that are served by the fan system. For multiple deck systems, a separate entry should be made for each deck.
Baseline Rules	The program shall automatically size the air flow at each thermal block to meet the loads. The design air flow rate calculation shall be based on a 20 degree temperature differential between supply air and the room air. The supply fan design air flow rate shall be the sum of the calculated design air flow for the thermal blocks served by the fan system.

Fan Control Method
Applicability	All fan systems
Definition	A description of how the supply (and return/relief) fan(s) are controlled. The options include: Constant volume Variable-flow, inlet or discharge dampers Variable-flow, inlet guide vanes Variable-flow, variable speed drive (VSD) Variable-flow, variable pitch blades Variable-flow, other Two-speed Constant volume, cycling (fan cycles with heating and cooling)
Units	List (see above)
Input Restrictions	As designed
Baseline Rules	Applicable to variable air volume systems Based on the prescribed system type. Refer to the HVAC System Map in [bookref id="hvac-mapping"].

[table title="Baseline Building Fan Control Method" id="baseline -bilding-fan-control-method"]

Baseline building System	Fan Control Method
System 1 – PTAC	Constant volume
System 2 – PTHP	Constant volume
System 3 – PSZ-AC	Constant volume
System 4 – PSZ-HP	Constant volume
System 5 – Packaged VAV with Reheat	Variable-flow, variable speed drive (VSD)
System 6 – Packaged VAV with PFP boxes	Variable-flow, variable speed drive (VSD)
System 7 – VAV with Reheat	Variable-flow, variable speed drive (VSD)
System 8 – VAV with PFP boxes	Variable-flow, variable speed drive (VSD)

Supply Fan Brake Horsepower
Applicability	All fan systems, except those specified using the power-per-unit-flow method
Definition	The design shaft brake horsepower of the supply fan(s). This input does not need to be supplied if the Supply Fan kW is supplied.
Units	Horsepower (hp)
Input Restrictions	As designed. If this building descriptor is specified for the proposed design, then the Static Pressure and Fan Efficiency are not.
Baseline Rules	See [bookref id="baseline-building-fan-system-–-ASHRAE-standard-90.1-2007"] for ASHRAE Standard 90.1-2007. These tables give the baseline building fan system brake horsepower. The brake horsepower for the supply fan is this value times the Supply Fan Ratio (see above).

Supply Fan Static Pressure
Applicability	All fan systems, except those specified using the power-per-unit-flow method
Definition	The design static pressure for the supply fan. This is important for both fan electric energy usage and duct heat gain calculations.
Units	Inches of water column (in. H₂0)
Input Restrictions	As designed. The design static pressure for the supply fan does not need to be specified if the supply fan brake horsepower (bhp) is specified.
Baseline Rules	Not applicable. When Static Pressure and Fan Efficiency are entered for the proposed design, the baseline building shall use Brake Horsepower.

Supply Fan Efficiency
Applicability	All fan systems, except those specified using the power-per-unit-flow method
Definition	The efficiency of the fan at design conditions
Units	Unitless
Input Restrictions	As designed. The supply fan efficiency does not need to be specified if the supply fan brake horsepower (bhp) is specified.
Baseline Rules	Not applicable. When Static Pressure and Fan Efficiency are entered for the proposed design, the baseline building shall use Brake Horsepower.

Supply Motor Efficiency
Applicability	All supply fans, except those specified using the power-per-unit-flow method
Definition	The full-load efficiency of the motor serving the supply fan
Units	Unitless
Input Restrictions	As designed. Not applicable when the power-per-unit-flow method is used.
Baseline Rules	From Table 10.8 of ASHRAE Standard 90.1-2007

Fan Position
Applicability	All supply fans
Definition	The position of the supply fan relative to the cooling coil. The configuration is either draw through (fan is downstream of the coil) or blow through (fan is upstream of the coil).
Units	List (see above)
Input Restrictions	As designed.
Baseline Rules	Draw through

Motor Position
Applicability	All supply fans
Definition	The position of the supply fan motor relative to the cooling air stream. The choices are: in the air stream or out of the air stream.
Units	List (see above)
Input Restrictions	As designed.
Baseline Rules	In the air stream

Fan Part-Flow Power Curve

Applicability

All variable flow fan systems

Definition

A part-load power curve which represents the percentage full-load power draw of the supply fan as a function of the percentage full-load air flow. The curve is typically represented as a quadratic equation with an absolute minimum power draw specified.

Units

Unitless ratio

Input Restrictions

As designed. The default fan curve shall be selected from Equation (6.7.3-1) and [bookref id="fan-curve-default-values"] for the type of fan specified in the proposed design.

(6.7.3-1)

$Greater \;of$

$PLR = a + b \cdot FanRatio + c \cdot FanRatio^2 + d \cdot FanRatio^3$

$PLR = PowerMin $

where

PLR	Ratio of fan power at part load conditions to full load fan power
PowerMin	Minimum fan power
FanRatio	Ratio of cfm at part-load to full-load cfm
a, b, c and d	Constants from [bookref id="fan-curve-default-values"] below

[table title="Fan Curve Default Values" id="fan-curve-default-values"]

Fan Type - Control Type	a	b	c	d	%Power_Min
AF or BI riding the curve^a	0.1631	1.5901	-0.8817	0.1281	70%
AF or BI with inlet vanes^a	0.9977	-0.659	0.9547	-0.2936	50%
FC riding the curve^a	0.1224	0.612	0.5983	-0.3334	30%
FC with inlet vanes^a	0.3038	-0.7608	2.2729	-0.8169	30%
Vane-axial with variable pitch blades^a	0.1639	-0.4016	1.9909	-0.7541	20%
Any fan with VSD (use for baseline building)^b	0.0013	0.1470	0.9506	-0.0998	20%
VSD with static pressure reset^c	-0.0031	0.0991	1.0268	-0.1128	20%
Data Sources: a. ECB Compliance Supplement, public review draft, Version 1.2, March 1996, but adjusted to be relatively consistent with the curve specified in the PRM. b. The fan curve for VSD is specified in Table G3.1.3.15 c. Advanced VAV System Design Guide, California Energy Commission, CEC Publication 500,-03-082 A-11, April 2005, but adjusted to be relatively consistent with the curve specified in the PRM..

Baseline Rules

Not applicable for baseline building systems 1-4. The curve for VSD fans shall be used for baseline building systems 5-8 with no adjustment for static pressure setpoint reset.

Supply Fan kW

Applicability

Fan systems that use the power-per-unit-flow method

Definition

The supply fan power per unit of flow.

Units

kW/cfm

Input Restrictions

As designed or specified in the manufacturers’ literature. For units with rated total cooling capacities less than 120,000 Btu/h, the user may default to a value calculated as follows:

(6.7.3-2)

$$ Fan_{kw} = 0.365 \times \frac{Q_{rated}}{30,000} $$

where

Fan_kw	The supply fan power (kW)
Q_rated	The rated total cooling capacity (Btu/h)

Baseline Rules

Applicable when the baseline building uses the power-per-unit-flow method. Fan power is determined using [bookref id="baseline-building-fan-system-–-ASHRAE-standard-90.1-2007"] for ASHRAE Standard 90.1-2007. This power is then multiplied by the supply fan ratio.

Relief Fans

The baseline building has a return fan when the baseline building system is type 3 through 8 and the proposed design has a return fan.

Plenum Zone
Applicability	Any system with return ducts or return air plenum
Definition	A reference to the thermal block that serves as return plenum or where the return ducts are located
Units	Text, unique
Input Restrictions	As designed
Baseline Rules	Applicable when the baseline building has a return fan. Same as the proposed design when the proposed design has a plenum, otherwise, the return air ducts are assumed to be located in the space.

Return Air Path
Applicability	Any system with return ducts or return air plenum
Definition	Describes the return path for air. This can be one of the following: ducted return; plenum return; or direct-to-unit.
Units	List (see above)
Input Restrictions	As designed
Baseline Rules	Applicable when the baseline building has a return fan. For baseline building systems 1 and 2, the return air path shall be direct-to-unit. For baseline building systems 3 through 8 and when the proposed design is direct-to-unit, the baseline building shall be ducted return, otherwise the baseline building return air path shall be same as proposed design.

Return/Relief Air Rated Capacity
Applicability	All systems with a return or relief fan
Definition	The design air flow fan capacity of the return or relief fan(s). This sets the 100% fan flow point for the part-load curve (see below).
Units	cfm
Input Restrictions	As designed
Baseline Rules	Applicable when the baseline building has a return fan. The return fan air Rated Capacity shall be equal to the baseline building supply fan capacity less exhaust air flow.

Return/Relief Fan Brake Horsepower
Applicability	Any system with return or relief fans that uses the brake horsepower method
Definition	The design shaft brake horsepower of the return/relief fan(s)
Units	Brake horsepower (bhp)
Input Restrictions	As designed
Baseline Rules	Applicable when the baseline building has a return fan. The bhp of the return fan shall be the fan system brake horsepower (see [bookref id="baseline-building-fan-system-–-ASHRAE-standard-90.1-2007"]) times the return fan ratio. In other words, brake horsepower is allocated in proportion to the proposed design.

Return/Relief Design Static Pressure
Applicability	Any system with return or relief fans that uses the static pressure method
Definition	The design static pressure for return fan system. This is important for both fan electric energy usage and duct heat gain calculations.
Units	Inches of water column (in. H₂0)
Input Restrictions	As designed. The design static pressure for the return fan does not need to be specified if the return fan brake horsepower (bhp) is specified.
Baseline Rules	Not applicable. When Static Pressure and Fan Efficiency are entered for the proposed design, the baseline building shall use Brake Horsepower.

Return/Relief Fan Efficiency
Applicability	Any system with return or relief fans that uses the static pressure method
Definition	The efficiency of the fan at design conditions
Units	Unitless
Input Restrictions	As designed. The return/relief fan efficiency does not need to be specified if the return fan brake horsepower (bhp) is specified.
Baseline Rules	Not applicable. When Static Pressure and Fan Efficiency are entered for the proposed design, the baseline building shall use Brake Horsepower.

Return/Relief Motor Efficiency
Applicability	All return fans, except those specified using the power-per-unit-flow method
Definition	The full-load efficiency of the motor serving the supply fan
Units	Unitless
Input Restrictions	As designed. Not applicable when the power-per-unit-flow method is used.
Baseline Rules	From Table 10.8 of ASHRAE Standard 90.1-2007

Motor Position
Applicability	All return fans
Definition	The position of the supply fan motor relative to the cooling air stream. The choices are: in the air stream or out of the air stream.
Units	List (see above)
Input Restrictions	As designed.
Baseline Rules	In the air stream

Fan Part-Flow Power Curve
Applicability	All return fans for variable flow fan systems.
Definition	A part-load power curve which represents the percentage full-load power draw of the supply fan as a function of the percentage full-load air flow.
Units	Unitless ratio
Input Restrictions	As designed. The default fan curve shall be selected from Equation (6.7.3-1) and [bookref id="fan-curve-default-values"] for the type of fan specified in the proposed design.
Baseline Rules	Not applicable for baseline building systems 1-4. The curve for VSD fans shall be used for baseline building systems 5-8 that have a return/relief fan.

Return/Relief Fan kW
Applicability	Any system with a return fan
Definition	The supply fan power per unit of flow
Units	kW/cfm
Input Restrictions	As specified in the manufacturers’ literature
Baseline Rules	Applicable when the baseline building uses the power-per-unit-flow method. Fan power is determined using [bookref id="baseline-building-fan-system-–-ASHRAE-standard-90.1-2007"] for ASHRAE Standard 90.1-2007. This power is then multiplied by the return fan ratio.

Exhaust Fan Systems

Exhaust fans include toilet exhaust, kitchen exhaust, as well as fume hoods in laboratories and other spaces. Some systems typically operate at constant flow, while flow varies for other systems depending on, for instance, the position of the sash for fume hoods. Exhaust fan flow is specified and scheduled for each thermal block. An exhaust fan system may serve multiple thermal blocks. The baseline building has exhaust fans when the proposed design has exhaust fans. The exhaust air flow is the same for the baseline building and the proposed design.

Exhaust Fan Name
Applicability	All exhaust systems serving multiple thermal blocks
Definition	A unique descriptor for each exhaust fan. This should be keyed to the construction documents, if possible, to facilitate plan checking. Exhaust rates and schedules at the thermal block level refer to this name.
Units	Text, unique
Input Restrictions	Where applicable, this should match the tags that are used on the plans.
Baseline Rules	The baseline building will have an exhaust system that corresponds to the proposed design. The name can be identical to that used for the proposed design or some other appropriate name may be used.

Exhaust Fan System Modeling Method
Applicability	All exhaust fan systems
Definition	Software commonly models fans in three ways. See definition for supply system modeling method.
Units	List: power-per-unit-flow, static pressure or brake horsepower
Input Restrictions	As designed
Baseline Rules	If the proposed design uses the power-per-unit-flow method, the baseline building shall also use this method, otherwise the baseline building shall use the brake horsepower method.

Exhaust Fan Rated Capacity
Applicability	All exhaust systems
Definition	The rated design air flow rate of the exhaust fan system. This building descriptor defines the 100% flow case for the part-flow curve. Actual air flow is the sum of the flow specified for each thermal block, as modified by the schedule for each thermal block.
Units	cfm
Input Restrictions	As designed
Baseline Rules	Same as proposed design

Fan Control Method
Applicability	All exhaust fan systems
Definition	A description of how the exhaust fan(s) are controlled. The options include: Constant volume Two-speed Variable-flow, inlet or discharge dampers Variable-flow, inlet guide vanes Variable-flow, variable speed drive (VSD) Variable-flow, variable pitch blades
Units	List (see above)
Input Restrictions	As designed, however, when exhaust fan flow at the thermal block level is varied through a schedule, one of the variable-flow options shall be specified.
Baseline Rules	The baseline building exhaust fan control shall generally be the same as the proposed design. For laboratories that have exhaust flow of 5,000 cfm or more, the baseline building exhaust flow shall vary in response to scheduled fume hood exhaust and lab zone airflow schedules. Fume hood exhaust flow control shall be the same as design, and general exhaust (relief) shall be VSD.

Exhaust Fan Schedule
Applicability	All exhaust fan systems
Definition	A schedule that indicates when the exhaust fan system is available for operation. Exhaust fan flow is specified at the thermal block level.
Units	Data structure: schedule, on/off
Input Restrictions	The exhaust fan system shall be available during all periods when one or more thermal blocks served by the system are scheduling exhaust.
Baseline Rules	Same as the proposed design

Exhaust Fan Brake Horsepower
Applicability	All exhaust fan systems
Definition	The design shaft brake horsepower of the exhaust fan(s).
Units	Brake horsepower (bhp)
Input Restrictions	As designed
Baseline Rules	The bhp for the baseline building is the total system fan horsepower from [bookref id="baseline-building-fan-system-–-ASHRAE-standard-90.1-2007"] times the exhaust fan ratio.

Exhaust Fan Design Static Pressure
Applicability	Any system with return or relief fans that uses the static pressure method
Definition	The design static pressure for exhaust fan system. This is important for both fan electric energy usage and duct heat gain calculations.
Units	Inches of water column (in. H₂0)
Input Restrictions	As designed. The design static pressure for the exhaust fan does not need to be specified if the exhaust fan brake horsepower (bhp) is specified.
Baseline Rules	Not applicable. When static pressure and fan efficiency are entered for the proposed design, the baseline building shall use brake horsepower.

Exhaust Fan Efficiency
Applicability	Any exhaust fan system that uses the static pressure method
Definition	The efficiency of the exhaust fan at rated capacity
Units	Unitless
Input Restrictions	As designed. The exhaust fan efficiency does not need to be specified if the return fan brake horsepower (bhp) is specified.
Baseline Rules	Not applicable. When static pressure and fan efficiency are entered for the proposed design, the baseline building shall use brake horsepower.

Exhaust Fan Motor Efficiency
Applicability	All exhaust fan systems
Definition	The full-load efficiency of the motor serving the exhaust fan
Units	Unitless
Input Restrictions	As designed
Baseline Rules	From Table 10.8 of ASHRAE Standard 90.1-2007

Fan Part-Flow Power Curve
Applicability	All variable flow exhaust fan systems
Definition	A part-load power curve which represents the ratio full-load power draw of the exhaust fan as a function of the ratio full-load air flow.
Units	Unitless ratio
Input Restrictions	As designed. The default fan curve shall be selected from Equation (6.7.3-1) and [bookref id="fan-curve-default-values"] for the type of fan specified in the proposed design.
Baseline Rules	The baseline building fan curve shall be selected from Equation (6.7.3-1) and [bookref id="fan-curve-default-values"] for the type of fan specified in the proposed design.

Exhaust Fan KW
Applicability	All exhaust systems
Definition	The fan power of the exhaust fan per unit of flow. This building descriptor is applicable only with the power-per-unit-flow method.
Units	W/cfm
Input Restrictions	As designed.
Baseline Rules	The fan system power from [bookref id="baseline-building-fan-system-–-ASHRAE-standard-90.1-2007"]

Baseline Building Fan System Summary

The baseline building fan system is summarized in this section. See Figure 6.1.2-1 for the HVAC baseline building system mapping.

Total baseline building fan system power for the baseline building fan systems is given in Table 6.7.3-1. In this table, "cfms" is the supply fan air flow at peak design conditions. This is calculated for the baseline building with the sizing procedure described in Figure 2.4-1. This brake horsepower includes the supply fan, the return fan, and exhaust fans. Exhaust fans include kitchen hoods, toilets, fume hoods, and other miscellaneous fans that operate at design conditions.

Table 6.7.3-1: Baseline Building Fan System – ASHRAE Standard 90.1 2010

	System Types 1-2	System Types 3-4	System Types 5-8	System Types 9-10
Brake Horsepower (bhp)	Not applicable	0.00094 x cfm_s + A	0.0013 x cfm_s + A	Not Applicable
Fan Motor Efficiency (hm)	Not applicable	ASHRAE Standard 90.1-2007, Table 10.8	ASHRAE Standard 90.1-2007, Table 10.8	Not Applicable
Fan Power (W)	0.3 x cfm_s	(bhp x 746)/_$\eta$m	(bhp x 746)/_$\eta$m	0.3 x cfms OR 0.054 x CFMnmc
The term “A” for system types 3-8, is calculated based on equipment in the proposed design using the procedure in Table 6.5.3.1.1B of ASHRAE Standard 90.1-2010. This accounts for various additional fan pressure drops associated with special conditions. *CFMnmc is the baseline non-mechanical cooling fan airflow in cfm. This alternate equation is only used if there is a non-mechanical cooling system in place.

When the proposed design has exhaust fans (toilets or kitchens), return fans, or fume hood exhaust systems, the baseline building has the same systems. The brake horsepower determined from Table 6.7.3-1 is allocated to these baseline building fan systems proportionally to the allocation in the proposed design. The allocation of brake horsepower to the supply fan, the return and any exhaust or fume hood fans is based on the ratios described below.

Supply Fan Ratio
Applicability	Systems that serve thermal blocks that have exhaust, fume hoods, kitchen exhaust or return fans
Definition	The ratio of supply fan brake horsepower in the proposed design to total fan system brake horsepower for the proposed design at design conditions
Units	Unitless ratio
Input Restrictions	Derived from other building descriptors
Baseline Rules	Same as proposed design

Return Fan Ratio
Applicability	Systems that serve thermal blocks that have exhaust, fume hoods, kitchen exhaust or return fans
Definition	The ratio of return fan brake horsepower in the proposed design to total fan system brake horsepower for the proposed design at design conditions
Units	Unitless ratio
Input Restrictions	Derived from other building descriptors
Baseline Rules	Same as proposed design

Exhaust Fan Ratio
Applicability	Systems that serve thermal blocks that have exhaust, fume hoods, kitchen exhaust or return fans
Definition	The ratio of exhaust fan brake horsepower in the proposed design to total fan system brake hp for the proposed design at design conditions. Exhaust fans include toilet exhaust, kitchen hoods and other miscellaneous exhaust. Fume hood exhaust is treated separately.
Units	Unitless ratio
Input Restrictions	Derived from other building descriptors. In the event that a common exhaust system serves thermal blocks that are served by different HVAC systems, the brake horsepower shall be divided in proportion to design cfm.
Baseline Rules	Same as proposed design

Supply Fans

Fan System Modeling Method
Applicability	All fan systems
Definition	Software commonly models fans in three ways. Power-per-unit-flow. The simple method is for the user to enter the electric power per unit of flow (W/cfm). This method is commonly used for unitary equipment and other small fan systems. Static pressure. A more detailed method is to model the fan as a system whereby the static pressure, fan efficiency, part-load curve, and motor efficiency are specified at design conditions. Break horsepower. A third method is to specify brake horsepower at design conditions instead of fan efficiency and static pressure. This is a variation of the second method whereby brake horsepower is specified in lieu of static pressure and fan efficiency. The latter two methods are commonly used for VAV and other larger fan systems.
Units	List: power-per-unit-flow, static pressure or brake horsepower
Input Restrictions	As designed. The power-per-unit-flow method shall be used when no fan performance data is available for the proposed design cooling system, e.g. only EER or SEER are available.
Baseline Rules	If the proposed design uses the power-per-unit-flow method, the baseline building shall also use this method, otherwise the baseline building shall use the brake horsepower method.

Supply Fan Design Air Rated Capacity
Applicability	All fan systems
Definition	The design air flow rate of the supply fan(s) at design conditions. This building descriptor sets the 100% point for the fan part-load curve.
Units	cfm
Input Restrictions	As designed. This input should be at least as great as the sum of the design air flow specified for each of the thermal blocks that are served by the fan system. For multiple deck systems, a separate entry should be made for each deck.
Baseline Rules	The program shall automatically size the air flow at each thermal block to meet the loads. The design air flow rate calculation shall be based on a 20 degree temperature differential between supply air and the room air. The supply fan design air flow rate shall be the sum of the calculated design air flow for the thermal blocks served by the fan system. For laboratory spaces, the design air flow rate calculation shall be based on a 17 degree temperature differential rather than 20. For baseline systems 9 and 10, the design air flow rate calculation shall be based on a supply air temperature setpoint of 105 degrees.

Fan Control Method
Applicability	All fan systems
Definition	A description of how the supply (and return/relief) fan(s) are controlled. The options include: Constant volume Variable-flow, inlet or discharge dampers Variable-flow, inlet guide vanes Variable-flow, variable speed drive (VSD) Variable-flow, variable pitch blades Variable-flow, other Two-speed Constant volume, cycling (fan cycles with heating and cooling)
Units	List (see above)
Input Restrictions	As designed
Baseline Rules	Applicable to variable air volume systems Based on the prescribed system type. Refer to the HVAC System Map in Figure 6.1.2-1.

Table 6.7.3-2: Baseline Building Fan Control Method

Baseline building System	Fan Control Method
System 1 – PTAC	Constant volume
System 2 – PTHP	Constant volume
System 3 – PSZ-AC	Constant volume
System 4 – PSZ-HP	Constant volume
System 5 – Packaged VAV with Reheat	Variable-flow, variable speed drive (VSD)
System 6 – Packaged VAV with PFP boxes	Variable-flow, variable speed drive (VSD)
System 7 – VAV with Reheat	Variable-flow, variable speed drive (VSD)
System 8 – VAV with PFP boxes	Variable-flow, variable speed drive (VSD)
System 9 – Heating and Ventilation	Constant Volume
System 10 – Heating and Ventilation	Constant Volume
*Effective 1/1/2012, all air-conditioning equipment and air-handling units with dx cooling and a cooling capacity greater than or equal to 110,000 Btu/h that serve single zones shall have supply fans controlled by two-speed motors or variable speed drives. At cooling demands less than or equal to 50% , the supply fan controls shall reduce the airflow to no greater than the larger of the following: 1)1/2 of the full fan speed or 2)the minimum outdoor air.

Supply Fan Brake Horsepower
Applicability	All fan systems, except those specified using the power-per-unit-flow method
Definition	The design shaft brake horsepower of the supply fan(s). This input does not need to be supplied if the Supply Fan kW is supplied.
Units	Horsepower (hp)
Input Restrictions	As designed. If this building descriptor is specified for the proposed design, then the Static Pressure and Fan Efficiency are not.
Baseline Rules	See Table 6.7.2-1 for ASHRAE Standard 90.1-2007. These tables give the baseline building fan system brake horsepower. The brake horsepower for the supply fan is this value times the Supply Fan Ratio (see above).

Supply Fan Static Pressure
Applicability	All fan systems, except those specified using the power-per-unit-flow method
Definition	The design static pressure for the supply fan. This is important for both fan electric energy usage and duct heat gain calculations.
Units	Inches of water column (in. H₂0)
Input Restrictions	As designed. The design static pressure for the supply fan does not need to be specified if the supply fan brake horsepower (bhp) is specified.
Baseline Rules	Not applicable. When Static Pressure and Fan Efficiency are entered for the proposed design, the baseline building shall use Brake Horsepower.

Supply Fan Efficiency
Applicability	All fan systems, except those specified using the power-per-unit-flow method
Definition	The efficiency of the fan at design conditions
Units	Unitless
Input Restrictions	As designed. The supply fan efficiency does not need to be specified if the supply fan brake horsepower (bhp) is specified.
Baseline Rules	Not applicable. When Static Pressure and Fan Efficiency are entered for the proposed design, the baseline building shall use Brake Horsepower.

Supply Motor Efficiency
Applicability	All supply fans, except those specified using the power-per-unit-flow method
Definition	The full-load efficiency of the motor serving the supply fan
Units	Unitless
Input Restrictions	As designed. Not applicable when the power-per-unit-flow method is used.
Baseline Rules	From Table 10.8 of ASHRAE Standard 90.1-2007

Fan Position
Applicability	All supply fans
Definition	The position of the supply fan relative to the cooling coil. The configuration is either draw through (fan is downstream of the coil) or blow through (fan is upstream of the coil).
Units	List (see above)
Input Restrictions	As designed.
Baseline Rules	Draw through

Motor Position
Applicability	All supply fans
Definition	The position of the supply fan motor relative to the cooling air stream. The choices are: in the air stream or out of the air stream.
Units	List (see above)
Input Restrictions	As designed.
Baseline Rules	In the air stream

Fan Part-Flow Power Curve

Applicability

All variable flow fan systems

Definition

A part-load power curve which represents the percentage full-load power draw of the supply fan as a function of the percentage full-load air flow. The curve is typically represented as a quadratic equation with an absolute minimum power draw specified.

Units

Unitless ratio

Input Restrictions

As designed. The default fan curve shall be selected from Equation (6.7.3-1) and Table 6.7.3-3 for the type of fan specified in the proposed design.

(6.7.3-1)

$Greater \;of$

$PLR = a + b \cdot FanRatio + c \cdot FanRatio^2 + d \cdot FanRatio^3$

$PLR = PowerMin $

where

PLR	Ratio of fan power at part load conditions to full load fan power
PowerMin	Minimum fan power
FanRatio	Ratio of cfm at part-load to full-load cfm
a, b, c and d	Constants from Table 7.7.3-3 below

Table 6.7.3-3:Fan Curve Default Values

Fan Type - Control Type	a	b	c	d	%Power_Min
AF or BI riding the curve^a	0.1631	1.5901	-0.8817	0.1281	70%
AF or BI with inlet vanes^a	0.9977	-0.659	0.9547	-0.2936	50%
FC riding the curve^a	0.1224	0.612	0.5983	-0.3334	30%
FC with inlet vanes^a	0.3038	-0.7608	2.2729	-0.8169	30%
Vane-axial with variable pitch blades^a	0.1639	-0.4016	1.9909	-0.7541	20%
Any fan with VSD (use for baseline building)^b	0.0013	0.1470	0.9506	-0.0998	20%
VSD with static pressure reset^c	-0.0031	0.0991	1.0268	-0.1128	20%
Data Sources: a. ECB Compliance Supplement, public review draft, Version 1.2, March 1996, but adjusted to be relatively consistent with the curve specified in the PRM. b. The fan curve for VSD is specified in Table G3.1.3.15 c. Advanced VAV System Design Guide, California Energy Commission, CEC Publication 500,-03-082 A-11, April 2005, but adjusted to be relatively consistent with the curve specified in the PRM..

Baseline Rules

Not applicable for baseline building systems 1-4. The curve for VSD fans shall be used for baseline building systems 5-8 with no adjustment for static pressure setpoint reset.

Supply Fan kW

Applicability

Fan systems that use the power-per-unit-flow method

Definition

The supply fan power per unit of flow.

Units

kW/cfm

Input Restrictions

As designed or specified in the manufacturers’ literature. For units with rated total cooling capacities less than 120,000 Btu/h, the user may default to a value calculated as follows:

(6.7.3-2)

$$ Fan_{kw} = 0.365 \times \frac{Q_{rated}}{30,000} $$

where

Fan_kw	The supply fan power (kW)
Q_rated	The rated total cooling capacity (Btu/h)

Baseline Rules

Applicable when the baseline building uses the power-per-unit-flow method. Fan power is determined using Table 6.7.3-1 for ASHRAE Standard 90.1-2007. This power is then multiplied by the supply fan ratio.

Relief Fans

The baseline building has a return fan when the baseline building system is type 3 through 8 and the proposed design has a return fan.

Plenum Zone
Applicability	Any system with return ducts or return air plenum
Definition	A reference to the thermal block that serves as return plenum or where the return ducts are located
Units	Text, unique
Input Restrictions	As designed
Baseline Rules	Applicable when the baseline building has a return fan. Same as the proposed design when the proposed design has a plenum, otherwise, the return air ducts are assumed to be located in the space.

Return Air Path
Applicability	Any system with return ducts or return air plenum
Definition	Describes the return path for air. This can be one of the following: ducted return; plenum return; or direct-to-unit.
Units	List (see above)
Input Restrictions	As designed
Baseline Rules	Applicable when the baseline building has a return fan. For baseline building systems 1 and 2, the return air path shall be direct-to-unit. For baseline building systems 3 through 8 and when the proposed design is direct-to-unit, the baseline building shall be ducted return, otherwise the baseline building return air path shall be same as proposed design.

Return/Relief Air Rated Capacity
Applicability	All systems with a return or relief fan
Definition	The design air flow fan capacity of the return or relief fan(s). This sets the 100% fan flow point for the part-load curve (see below).
Units	cfm
Input Restrictions	As designed
Baseline Rules	Applicable when the baseline building has a return fan. The return fan air Rated Capacity shall be equal to the baseline building supply fan capacity less exhaust air flow.

Return/Relief Fan Brake Horsepower
Applicability	Any system with return or relief fans that uses the brake horsepower method
Definition	The design shaft brake horsepower of the return/relief fan(s)
Units	Brake horsepower (bhp)
Input Restrictions	As designed
Baseline Rules	Applicable when the baseline building has a return fan. The bhp of the return fan shall be the fan system brake horsepower (see Table 6.7.3-1) times the return fan ratio. In other words, brake horsepower is allocated in proportion to the proposed design.

Return/Relief Design Static Pressure
Applicability	Any system with return or relief fans that uses the static pressure method
Definition	The design static pressure for return fan system. This is important for both fan electric energy usage and duct heat gain calculations.
Units	Inches of water column (in. H₂0)
Input Restrictions	As designed. The design static pressure for the return fan does not need to be specified if the return fan brake horsepower (bhp) is specified.
Baseline Rules	Not applicable. When Static Pressure and Fan Efficiency are entered for the proposed design, the baseline building shall use Brake Horsepower.

Return/Relief Fan Efficiency
Applicability	Any system with return or relief fans that uses the static pressure method
Definition	The efficiency of the fan at design conditions
Units	Unitless
Input Restrictions	As designed. The return/relief fan efficiency does not need to be specified if the return fan brake horsepower (bhp) is specified.
Baseline Rules	Not applicable. When Static Pressure and Fan Efficiency are entered for the proposed design, the baseline building shall use Brake Horsepower.

Return/Relief Motor Efficiency
Applicability	All return fans, except those specified using the power-per-unit-flow method
Definition	The full-load efficiency of the motor serving the supply fan
Units	Unitless
Input Restrictions	As designed. Not applicable when the power-per-unit-flow method is used.
Baseline Rules	From Table 10.8 of ASHRAE Standard 90.1-2007

Motor Position
Applicability	All return fans
Definition	The position of the supply fan motor relative to the cooling air stream. The choices are: in the air stream or out of the air stream.
Units	List (see above)
Input Restrictions	As designed.
Baseline Rules	In the air stream

Fan Part-Flow Power Curve
Applicability	All return fans for variable flow fan systems.
Definition	A part-load power curve which represents the percentage full-load power draw of the supply fan as a function of the percentage full-load air flow.
Units	Unitless ratio
Input Restrictions	As designed. The default fan curve shall be selected from Equation (6.7.3-1) and Table 6.7.3-3 for the type of fan specified in the proposed design.
Baseline Rules	Not applicable for baseline building systems 1-4. The curve for VSD fans shall be used for baseline building systems 5-8 that have a return/relief fan.

Return/Relief Fan kW
Applicability	Any system with a return fan
Definition	The supply fan power per unit of flow
Units	kW/cfm
Input Restrictions	As specified in the manufacturers’ literature
Baseline Rules	Applicable when the baseline building uses the power-per-unit-flow method. Fan power is determined using Table 6.7.3-1 for ASHRAE Standard 90.1-2007. This power is then multiplied by the return fan ratio.

Exhaust Fan Systems

Exhaust fans include toilet exhaust, kitchen exhaust, as well as fume hoods in laboratories and other spaces. Some systems typically operate at constant flow, while flow varies for other systems depending on, for instance, the position of the sash for fume hoods. Exhaust fan flow is specified and scheduled for each thermal block. An exhaust fan system may serve multiple thermal blocks. The baseline building has exhaust fans when the proposed design has exhaust fans. The exhaust air flow is the same for the baseline building and the proposed design.

Exhaust Fan Name
Applicability	All exhaust systems serving multiple thermal blocks
Definition	A unique descriptor for each exhaust fan. This should be keyed to the construction documents, if possible, to facilitate plan checking. Exhaust rates and schedules at the thermal block level refer to this name.
Units	Text, unique
Input Restrictions	Where applicable, this should match the tags that are used on the plans.
Baseline Rules	The baseline building will have an exhaust system that corresponds to the proposed design. The name can be identical to that used for the proposed design or some other appropriate name may be used.

Exhaust Fan System Modeling Method
Applicability	All exhaust fan systems
Definition	Software commonly models fans in three ways. See definition for supply system modeling method.
Units	List: power-per-unit-flow, static pressure or brake horsepower
Input Restrictions	As designed
Baseline Rules	If the proposed design uses the power-per-unit-flow method, the baseline building shall also use this method, otherwise the baseline building shall use the brake horsepower method.

Exhaust Fan Rated Capacity
Applicability	All exhaust systems
Definition	The rated design air flow rate of the exhaust fan system. This building descriptor defines the 100% flow case for the part-flow curve. Actual air flow is the sum of the flow specified for each thermal block, as modified by the schedule for each thermal block.
Units	cfm
Input Restrictions	As designed
Baseline Rules	Same as the proposed design except that baseline building kitchen exhaust rate may not exceed the maximum levels defined by ASHRAE 90.1-2010, Table 6.5.7.1.3.

Fan Control Method
Applicability	All exhaust fan systems
Definition	A description of how the exhaust fan(s) are controlled. The options include: Constant volume Two-speed Variable-flow, inlet or discharge dampers Variable-flow, inlet guide vanes Variable-flow, variable speed drive (VSD) Variable-flow, variable pitch blades
Units	List (see above)
Input Restrictions	As designed, however, when exhaust fan flow at the thermal block level is varied through a schedule, one of the variable-flow options shall be specified.
Baseline Rules	The baseline building exhaust fan control shall generally be the same as the proposed design. For laboratories that have exhaust flow of 5,000 cfm or more, the baseline building exhaust flow shall vary in response to scheduled fume hood exhaust and lab zone airflow schedules. Fume hood exhaust flow control shall be the same as design, and general exhaust (relief) shall be VSD. If a kitchen zone design exhaust rate is greater than 5,000 cfm, the baseline building system serving the kitchen shall be system type 5 or 7 with a demand ventilation system on 75% of the exhaust air. The system shall reduce exhaust and replacement air system airflow rates by 50% for one half of the kitchen occupied hours.

Exhaust Fan Schedule
Applicability	All exhaust fan systems
Definition	A schedule that indicates when the exhaust fan system is available for operation. Exhaust fan flow is specified at the thermal block level.
Units	Data structure: schedule, on/off
Input Restrictions	The exhaust fan system shall be available during all periods when one or more thermal blocks served by the system are scheduling exhaust.
Baseline Rules	Same as the proposed design

Exhaust Fan Brake Horsepower
Applicability	All exhaust fan systems
Definition	The design shaft brake horsepower of the exhaust fan(s).
Units	Brake horsepower (bhp)
Input Restrictions	As designed
Baseline Rules	The bhp for the baseline building is the total system fan horsepower from Table 6.7.3-1 times the exhaust fan ratio.

Exhaust Fan Design Static Pressure
Applicability	Any system with return or relief fans that uses the static pressure method
Definition	The design static pressure for exhaust fan system. This is important for both fan electric energy usage and duct heat gain calculations.
Units	Inches of water column (in. H₂0)
Input Restrictions	As designed. The design static pressure for the exhaust fan does not need to be specified if the exhaust fan brake horsepower (bhp) is specified.
Baseline Rules	Not applicable. When static pressure and fan efficiency are entered for the proposed design, the baseline building shall use brake horsepower.

Exhaust Fan Efficiency
Applicability	Any exhaust fan system that uses the static pressure method
Definition	The efficiency of the exhaust fan at rated capacity
Units	Unitless
Input Restrictions	As designed. The exhaust fan efficiency does not need to be specified if the return fan brake horsepower (bhp) is specified.
Baseline Rules	Not applicable. When static pressure and fan efficiency are entered for the proposed design, the baseline building shall use brake horsepower.

Exhaust Fan Motor Efficiency
Applicability	All exhaust fan systems
Definition	The full-load efficiency of the motor serving the exhaust fan
Units	Unitless
Input Restrictions	As designed
Baseline Rules	From Table 10.8 of ASHRAE Standard 90.1-2007

Fan Part-Flow Power Curve
Applicability	All variable flow exhaust fan systems
Definition	A part-load power curve which represents the ratio full-load power draw of the exhaust fan as a function of the ratio full-load air flow.
Units	Unitless ratio
Input Restrictions	As designed. The default fan curve shall be selected from Equation (6.7.3-1) and Table 6.7.3-3 for the type of fan specified in the proposed design.
Baseline Rules	The baseline building fan curve shall be selected from Equation (6.7.3-1) and Table 6.7.3-3 for the type of fan specified in the proposed design.

Exhaust Fan KW
Applicability	All exhaust systems
Definition	The fan power of the exhaust fan per unit of flow. This building descriptor is applicable only with the power-per-unit-flow method.
Units	W/cfm
Input Restrictions	As designed.
Baseline Rules	The fan system power from Table 6.7.3-1.

This section addresses:

90.1-2019

Baseline Building Fan System Summary

The baseline building fan system is summarized in this section. See Table 3 for the HVAC baseline building system mapping.

Total baseline building fan system power for the baseline building fan systems is given in the following sections as well as Table 53 and Table 54. Table 52 summarizes all descriptors for fan systems and their applicability to supply, return/relief, and exhaust fans.

Table 4 summarizes inputs for each of the three approaches for imputing system fan power (fan power method, brake horsepower method, and design pressure drop method).

· In these tables, CFMs is the baseline fan supply fan airflow at peak design conditions.

· The fan system power includes the supply fan, the return fan, and exhaust fans.

· Exhaust fans include kitchen hoods, toilets, fume hoods, and other miscellaneous fans that operate at design conditions.

When the proposed design has return fans, exhaust fans (toilets or kitchens), or fume hood exhaust systems, the baseline building has the same systems. Fan power will be allocated to the baseline supply, return, and exhaust fans based on the Fan System Power described below and the ratio of each fans power in the proposed design to the proposed design fan system power.

Table 52. Building Descriptor Applicability for Fan Systems

Inputs	Supply Fan	Return/ Relief Fan	Exhaust Fans (Hoods)
Modeling Method	yes	Same as supply	yes
Air Rated Capacity	yes	yes	yes
Plenum Zone	no	yes	no
Return Air Path	no	yes	no
Fan Control Method	no	Same as supply	yes
Brake Horsepower	yes	yes	yes
Static Pressure	yes	yes	yes
Fan Efficiency	yes	yes	yes
Motor Efficiency	yes	yes	yes
Fan Position	yes	no	no
Motor Position	yes	yes	no
Part-Load Power Curve	yes	yes	yes
Fan KW	yes	yes	yes

Table 53. Baseline Fan System Details for Fan System Power

System	Fan Power Method (W/cfm)	Brake Horsepower Method (bhp/cfm)	Design Pressure Drop (DPD) Method	Fan Motor Efficiency ŋm	Fan Mech Efficiency	DPD (If no additional pressure drop credits) (a)
1 & 2	0.3	W/cfm x ŋm x 0.00134	bhp/cfm x fan mech efficiency x 6356	80%	65%	1.33 in. w.g
3, 4, 12. & 13	(bhp x 746)/ŋm	0.00094 x CFMs + A	bhp/cfm x fan mech efficiency x 6356	Standard 90.1-2019, Table G3.9.1(a)	65%	3.88 in. w.g.
5 through 8	(bhp x 746)/ŋm	0.0013 x CFMs + A	bhp/cfm x fan mech efficiency x 6356	Standard 90.1-2019, Table G3.9.1(a)	65%	5.37 in. w.g.
9 & 10 supply fan	0.3	W/cfm x ŋm x 0.00134	bhp/cfm x fan mech efficiency x 6356	Standard 90.1-2019, Table G3.9.1(a)	65%	1.33 in. w.g.
9 & 10 non- mechanical cooling fan(b)	0.054	W/cfm x ŋm x 0.00134	bhp/cfm x fan mech efficiency x 6356	80%	65%	0.24 in. w.g.
11	(bhp x 746)/ŋm	0.00062 x CFMs + A	bhp/cfm x fan mech efficiency x 6356	Standard 90.1-2019, Table G3.9.1(a)	65%	2.56 in. w.g.

The term “A” for system types 3 through 8 is calculated based on equipment included in the proposed design

using the procedure in Table 6.5.3.1.1 of ASHRAE Standard 90.1-2019 and the airflows from the baseline

design. This accounts for various additional fan pressure drops associated with special conditions.

(a) Fan motor efficiency is the efficiency from Table G3.9.1 of Standard 90.1-2019 for the next motor size

greater than the bhp.

(b) This alternate equation is only used if there is a non-mechanical cooling fan in place in the proposed design.

(c) If system qualified for additional pressure drop credits DPD should be calculated based on adjusted bhp.

Pressure Drop Adjustment
Applicability	Any system serving zones served by systems in the proposed design which qualify for pressure drop adjustments in Table 54
Definition	Adjustments to fan power limitations related to application-specific requirements as allowed by Standard 90.1-2019 Table 6.5.3.1-1
Units	List
Input Restrictions	As designed
Baseline Building	Calculated from Section 6.5.3.1-1 of Standard 90.1-2019 for baseline system fans. Pressure drop adjustment is based on the device from Table 54 being present in the proposed design.

Table 54. Baseline Building: Fan Power Limitation Pressure Drop Adjustment

Device	Adjustment
Credits
Return or exhaust systems required by code or accreditation standards to be fully ducted, or systems required to maintain air pressure differentials between adjacent rooms.	0.5 in. w.c. (2.15 in. w.c. for laboratory and vivarium systems)
Return and/or exhaust airflow control devices	0.5 in. w.c.
Exhaust filters, scrubbers, or other exhaust treatment	The pressure drop of device calculated at fan system design condition
Particulate filtration credit: MERV 9 through 12	0.5 in. w.c.
Particulate filtration credit: MERV 13 through 15	0.9 in. w.c.
Particulate filtration credit: MERV 16 and greater and electronically enhanced filters	Pressure drop calculated at 2x clean filter pressure drop at fan system design condition
Carbon and other gas-phase air cleaners	Clean filter pressure drop at fan system design condition
Biosafety cabinet	Pressure drop of device at fan system design condition
Energy recovery device and other coil runaround loop	(2.2 × Energy Recovery Effectiveness)—0.5 in w.c. for each airstream
Coil runaround loop	0.6 in. w.c. for each airstream
Evaporative humidifier/cooler in series with another cooling coil	Pressure drop of device at fan system design condition
Sound attenuation section	0.15 in. w.c.
Exhaust systems serving fume hoods	0.35 in. w.c.
Laboratory and vivarium exhaust systems in high-rise buildings	0.25 in. w.c./100 ft of vertical duct exceeding 75 ft.
Deductions
Systems without central cooling device	–0.6 in. w.c.
Systems without central heating device	–0.3 in. w.c.
Systems with central electric resistance heat	–0.2 in. w.c.

Fan Power Adjustment
Applicability	All fan systems qualifying for pressure drop adjustments as described above.
Definition	Standard 90.1-2019 specifies a “pressure drop adjustment” for fan systems with requirements for filtration or other process requirements.
Units	List
Input Restrictions	Derived from other building descriptors
Baseline Building	Pressure drop adjustment is calculated separately for each applicable device. Credit for each device is specified in the section above. A = sum of zones (PD_sum ´ CFMd_baseline/4131) Where: PD = Each applicable pressure drop adjustment from the proposed design CFMd = The design airflow through each applicable device in cfm from the baseline building Note: In scenarios where the proposed and baseline building have varying zone to system assignment, the pressure drop credit ‘A’ shall be calculated for each thermal zone in the proposed building, using the design flow rates in the proposed building design. For multi-zone systems in the proposed building, the pressure drop adjustment will be split for each zone based on the zone to system airflow ratio. The pressure drop adjustment for the baseline building will then be calculated by adjusting the calculated PDA by the ratio of baseline building design airflow rate to proposed building design air flow rate for each zone. The baseline system pressure drop adjustment will be a sum of the individual pressure drop adjustments of the applicable zones.

Supply Fan Ratio
Applicability	Systems that serve thermal blocks that have exhaust, fume hoods, kitchen exhaust, or return fans
Definition	The ratio of supply fan brake horsepower in the proposed design to total fan system brake horsepower for the proposed design at design conditions.
Units	Unitless fraction (0 to 1)
Input Restrictions	As designed
Baseline Building	Same as proposed

Return Fan Ratio
Applicability	Systems that serve thermal blocks that have exhaust, fume hoods, kitchen exhaust, or return fans
Definition	The ratio of return fan brake horsepower in the proposed design to total fan system brake horsepower for the proposed design at design conditions
Units	Unitless fraction (0 to 1)
Input Restrictions	Derived from other building descriptors
Baseline Building	Same as proposed

Exhaust Fan Ratio
Applicability	Systems that serve thermal blocks that have exhaust, fume hoods, kitchen exhaust, or return fans
Definition	The ratio of exhaust fan brake horsepower in the proposed design to total fan system brake hp for the proposed design at design conditions. Exhaust fans include toilet exhaust, kitchen hoods, and other miscellaneous exhaust. For fan systems with multiple exhaust fans, the exhaust fan ratios shall be calculated separately for each exhaust fan.
Units	Unitless ratio
Input Restrictions	Derived from other building descriptors. In the event that a common exhaust system serves thermal blocks that are served by different HVAC systems, the brake horsepower shall be divided in proportion to design cfm.
Baseline Building	Same as proposed

Supply Fans

Fan System Modeling Method
Applicability	All fan systems
Definition	Software commonly models fans in three ways. The simple method is for the user to enter the electric power per unit of flow (W/cfm). This method is commonly used for unitary equipment and other small fan systems. A more detailed method is to model the fan as a system whereby the static pressure, fan efficiency, and motor efficiency are specified at design conditions. A third method is to specify brake horsepower at design conditions instead of fan efficiency and static pressure. This is a variation of the second method whereby brake horsepower is specified in lieu of static pressure and fan efficiency.
Units	List: Power-Per-Unit-Flow, Design Pressure Drop, or Brake Horsepower
Input Restrictions	As designed
Baseline Building	Systems 1, 2, 9, and 10 should use power per unit flow if allowed by the software. If not allowed used one of the other methods as described in Table 54. All other baseline system shall use the brake horsepower method. If that method is not available, static pressure method should be used.

Supply Fan Design Air Rated Capacity
Applicability	All fan systems
Definition	The design airflow rate of the supply fan(s) at design conditions. This building descriptor sets the 100% point for the fan part-load curve.
Units	cfm
Input Restrictions	As designed
Baseline Building	The software shall automatically size the system airflow to meet the baseline building loads based on · a supply-air-to-room-air temperature difference of 20°F, · or the minimum outdoor airflow rate, · or the airflow rate required to comply with the applicable codes or accreditation standards, whichever is greater. The baseline system airflow is determined by the load to be met by the airflow and the 20°F (11°C) temperature difference. The loads to be used would be the design load as determined by the sizing runs specified in Section G3.1.2.2, not the cooling or heating capacity of the system as determined using the sizing factors, also specified in G3.1.2.2. Using the system cooling and heating capacity will result in oversized baseline system airflows and energy cost because of the oversizing factors used in G3.1.2.2. See additional discussion in Section 3.5.5.1 for VAV systems. spaces with special process requirements.) The supply fan design airflow rate shall be the sum of the calculated design airflow for the thermal zones served by the fan system. For laboratory spaces, the design airflow rate calculation shall be based on a 17°F temperature differential rather than 20°F. For baseline systems 9 and 10, the design supply airflow rates shall be based on the temperature difference between a SAT setpoint of 105°F and the design space heating temperature setpoint, the minimum outdoor airflow rate or the airflow rate required to comply with applicable codes, whichever is greater. If the proposed design HVAC system airflow rate based on latent loads greater than the same based on sensible loads, then the same supply-air-to-room humidity ratio difference (gr/lb) used to calculate the proposed design airflow should be used to calculate the design airflow rates for the baseline building.

Fan Control Method
Applicability	All fan systems
Definition	A description of how the supply (and return/relief) fan(s) is controlled. The options include: · Constant volume · Variable-flow, inlet or discharge dampers · Variable-flow, inlet guide vanes · Variable-flow, variable speed drive (VSD) · Variable-flow, variable pitch blades · Variable-flow, other · Two-speed · Constant volume, cycling (fan cycles with heating and cooling)
Units	List (see above)
Input Restrictions	As designed
Baseline Building	Based on the baseline system type, summarized in Table 55

Table 55. Baseline Building Fan Control Method

System No.	System Type	Fan Control
System 1	Package terminal air conditioner	Constant volume
System 2	Packaged terminal heat pump	Constant volume
System 3	Packaged roof top air conditioner	Constant volume
System 4	Packaged roof top heat pump	Constant volume
System 5	Packaged rooftop VAV with reheat	Variable volume, variable speed drive (VSD)
System 6	Packaged rooftop VAV with PFP boxes and reheat	Variable volume, VSD
System 7	Packaged rooftop VAV with reheat	Variable volume, VS
System 8	VAV with parallel fan-powered boxes and reheat	Variable volume, VSD
System 9	Warm air furnace, gas fired	Constant volume
System 10	Warm air furnace, electric	Constant volume
System 11	Single zone VAV	Variable volume, VSD
System 12	Single zone system (CHW and HW boiler)	Constant volume
System 13	Single zone system (CHW and electric resistance)	Constant volume

Supply Fan Brake Horsepower
Applicability	All fan systems, except those specified using the power-per-unit-flow method
Definition	The design shaft brake horsepower of the supply fan(s). This input does not need to be supplied if the supply fan kW is supplied.
Units	Horsepower (hp)
Input Restrictions	As designed. If this building descriptor is specified for the proposed design, then the static pressure and fan efficiency are not required.
Baseline Building	Fans for parallel fan-powered boxes are not included in fan power calculations. Table 53 of this document gives the baseline building fan system brake horsepower. The brake horsepower for the supply fan is this value times the supply fan ratio (see above).

Supply Fan Static Pressure
Applicability	All fan systems, except those specified using the power-per-unit-flow method
Definition	The design static pressure for the supply fan. This is important for both fan electric energy usage and duct heat gain calculations.
Units	Inches of water column (in. H2O)
Input Restrictions	As designed. The design static pressure for the supply fan does not need to be specified if the supply fan brake horsepower (bhp) is specified.
Baseline Building	The baseline building is defined by Table 53. This approach only works if the system has only a supply fan. If return/exhaust fans are also present in the system, then the supply fan bhp needs to be calculated and divided amongst the supply, return, and exhaust fans.

Supply Fan Efficiency
Applicability	All fan systems, except those specified using the power-per-unit-flow method
Definition	The efficiency of the fan at design conditions; this is the static efficiency and does not include motor losses
Units	Unitless
Input Restrictions	As designed. The supply fan efficiency does not need to be specified if the supply fan brake horsepower (bhp) is specified.
Baseline Building	The baseline supply fan efficiency shall be 65%.

Supply Motor Efficiency
Applicability	All supply fans, except those specified using the power-per-unit-flow method
Definition	The full-load efficiency of the motor serving the supply fan
Units	Unitless
Input Restrictions	As designed. Not applicable when the power-per-unit-flow method is used.
Baseline Building	For systems 1, 2, 9, and 10, motor efficiency is assumed to be 80%. The motor efficiency for systems 3 through 8 is determined from Table G3.9.1 of ASHRAE Standard 90.1-2019 (Table 56 below).

Table 56. Minimum Nominal Efficiency for Electric Motors (%)

Shaft Input Power	Full-Load Motor Efficiency, %
1	82.5
1.5	84
2	84
3	87.5
5	87.5
7.5	89.5
10	89.5
15	91
20	91
25	92.4
30	92.4
40	93
50	93
60	93.6
75	94.1
100	94.5
125	94.5
150	95
200	95

Fan Position
Applicability	All supply fans
Definition	The position of the supply fan relative to the cooling coil. The configuration is either draw through (fan is downstream of the coil) or blow through (fan is upstream of the coil).
Units	List (see above)
Input Restrictions	As designed
Baseline Building	Draw through

Motor Position
Applicability	All supply fans
Definition	The position of the supply fan motor relative to the cooling air stream. The choices are: in the air stream or out of the air stream.
Units	List (see above)
Input Restrictions	As designed
Baseline Building	In the air stream

Fan Part-Flow Power Curve

Applicability

All variable flow fan systems

Definition

A part-load power curve that represents the percentage full-load power draw of the supply fan as a function of the percentage full-load airflow. The curve is typically represented as a cubic equation with an absolute minimum power draw specified.

Units

Unitless ratio

Input Restrictions

The fan curve shall be selected from Equation (11) and Table 57 for the type of fan specified in the proposed design.

??????? ?? ???=?+?⋅????????+?⋅????????2+?⋅????????3 ???=????????

Where:

PLR = Ratio of fan power at part load conditions to full load fan power

PowerMin = Minimum fan power ratio

FanRatio = Ratio of cfm at part-load to full-load cfm

a, b, c and d = Constants from Table 57

Table 57. Fan Curve Default Values

Fan Type- Control Type	A	B	c	d	%PowerMin
Multi Zone VAV with Airfoil (AF) or Backward Incline (BI) riding the curve(a)	0.1631	1.5901	-0.8817	0.1281	70%
Multi Zone VAV with AF or BI with inlet vanes(a)	0.9977	-0.659	0.9547	-0.2936	50%
Multi Zone VAV with Forward Curved (FC) fans riding the curve(a)	0.1224	0.612	0.5983	-0.3334	30%
Multi Zone VAV with FC with inlet vanes(a)	0.3038	-0.7608	2.2729	-0.8169	30%
Multi Zone VAV with vane-axial with variable pitch blades(a)	0.1639	-0.4016	1.9909	-0.7541	20%
Multi Zone VAV with VSD and fixed SP setpoint(b)	0.0013	0.1470	0.9506	-0.0998	20%
Multi zone VAV with static pressure reset(c)	0.04076	0.0881	-0.0729	0.9437	10%
Single zone VAV fan(d)	0.027828	0.026583	-0.087069	1.030920	10%

Data Sources:

(a) ECB Compliance Supplement, public review draft, Version 1.2, March 1996, but adjusted to be relatively consistent with the curve specified in the PRM.

(b) The fan curve for VSD is specified in Table G3.1.3.15.

(c) This is the good SP reset VSD fan curve from the advanced VAV design guide used for MZVAV systems.

(d) This is the perfect SP reset VSD fan curve from the advanced VAV design guide used for SZVAV systems.

http://www.energy.ca.gov/2003publications/CEC-500-2003-082/CEC-500-2003-082-A-11.PDF

Baseline Building

Not applicable for baseline building systems 1 through 4. Baseline systems 5 through 8 will use the curve for “Multi zone VAV with fixed static pressure setpoint” curve. System 11 shall use the “Single zone VAV fan” curve. Constant volume fans are used for systems 9, 10, 12, and 13 and hence the descriptor is not applicable.

Supply Fan Power Index (kW/cfm)
Applicability	Fan systems that use the power-per-unit-flow method
Definition	The supply fan power per unit of flow
Units	kW/cfm
Input Restrictions	As designed or specified in the manufacturers’ literature
Baseline Building	Applicable when the baseline building uses the power-per-unit-flow method. Fan power is determined using Table 53 of this document. This power is then multiplied by the supply fan ratio.

Static Pressure Reset Controls
Applicability	All VAV fan systems. Baseline systems 5 through 8.
Definition	Static pressure reset controls, reset the fan static pressure for VAV systems-based zone damper position. For systems with DDC of individual zone boxes reporting to the central control panel, static pressure setpoint shall be reset based on the zone requiring the most pressure.
Units	Unitless
Input Restrictions	As designed. If static pressure reset is implemented in the proposed system, the curve for “Multi zone VAV with static pressure reset curve” shall be used.
Baseline Building	Not applicable for baseline building systems 1 through 4 or 9, 10, 11, 12, and 13. The curve for “Multi Zone VAV with VSD and fixed SP setpoint”’ shall be used for baseline building systems 5 through 8.

Return/ Relief Fans

System design supply airflow rates for the baseline building design shall be based on a supply-air-to room-air temperature difference of 20°F or the minimum outdoor airflow rate, or the airflow rate required to comply with applicable codes or accreditation standards, whichever is greater. For systems 3, 4, and 11 through 13, if return or relief fans are specified for systems serving the corresponding zones in the proposed design, the baseline building design shall also be modeled with fans serving the same functions. For systems 5 through 8, if return or relief fans are specified in the proposed building, then the baseline systems serving the corresponding zones will be modeled with a return/relief fan.

Plenum Zone
Applicability	Any system with return ducts or return air plenum
Definition	A reference to the thermal zone that serves as return plenum or where the return ducts are located
Units	Text, unique
Input Restrictions	As designed
Baseline Building	Applicable when the baseline building has a return fan. Same as the proposed design when the proposed design has a plenum; otherwise, the return air ducts are assumed to be located in the space.

Return Air Path
Applicability	Any system with return ducts or return air plenum
Definition	Describes the return path for air. This can be one of the following: ducted return; plenum return; or direct-to-unit.
Units	List (see above)
Input Restrictions	As designed
Baseline Building	For baseline building systems 1 and 2, the return air path shall be direct-to-unit. For baseline building systems 3 through 8 and 11 through 13 and when the proposed design is direct-to-unit, the baseline building shall be ducted return, otherwise the baseline building return air path shall be the same as proposed design.

Return/ Relief Air Rated Capacity
Applicability	All systems with a return or relief fan
Definition	The design airflow fan capacity of the return or relief fan(s). This sets the 100% fan flow point for the part-load curve (see below).
Units	cfm
Input Restrictions	As designed
Baseline Building	Applicable when the baseline building has a return fan. Return or relief fans shall be sized for the baseline system supply fan air quantity less the minimum outdoor air, or 90% of the supply fan air quantity, whichever is larger.

Return/ Relief Fan Brake Horsepower
Applicability	Any system with return or relief fans that uses the brake horsepower method
Definition	The design shaft brake horsepower of the return/relief fan(s)
Units	Brake horsepower (bhp)
Input Restrictions	As designed
Baseline Building	Applicable when the baseline building has a return fan. The bhp of the return fan shall be the system fan brake horsepower multiplied by the return fan ratio. In other words, brake horsepower is allocated in proportion to the proposed design.

Return/ Relief Design Static Pressure
Applicability	Any system with return or relief fans that uses the static pressure method
Definition	The design static pressure for return fan system. This is important for both fan electric energy usage and duct heat gain calculations.
Units	Inches of water column (in. H2O gauge)
Input Restrictions	As designed. The design static pressure for the return fan does not need to be specified if the return fan brake horsepower (bhp) is specified.
Baseline Building	Return fan static pressure = (Return fan BHP ´ 6356 ´ 0.65)/cfm return

Return/ Relief Fan Efficiency
Applicability	Any system with return or relief fans that uses the static pressure method
Definition	The efficiency of the fan at design conditions; this is the static efficiency and does not include the efficiency loss of the motor
Units	Unitless
Input Restrictions	As designed. The return/relief fan efficiency does not need to be specified if the return fan brake horsepower (bhp) is specified.
Baseline Building	65%

Return/ Relief Motor Efficiency
Applicability	All return fans, except those specified using the power-per-unit-flow method
Definition	The full-load efficiency of the motor serving the supply fan
Units	Unitless
Input Restrictions	As designed. Not applicable when the power-per-unit-flow method is used.
Baseline Building	For baseline systems 1, 2, 9, 10, 12, and 13 is 80%. For baseline systems 3 through 8 and 11, fan motor efficiency is determined from Table G3.9.1 of Standard 90.1-2019 for the next motor size greater than the bhp calculated, through the process described above, using a totally enclosed fan motor at 1800 rpm.

Motor Position
Applicability	All return fans
Definition	The position of the supply fan motor relative to the cooling air stream. The choices are in the air stream or out of the air stream.
Units	List (see above)
Input Restrictions	As designed
Baseline Building	In the air stream

Fan Part-Flow Power Curve
Applicability	All return fans for variable flow fan systems
Definition	A part-load power curve that represents the percentage full-load power draw of the return fan as a function of the percentage full-load airflow
Units	Unitless ratio
Input Restrictions	As designed. The default fan curve shall be selected from Equation (11) and Table 57 for the type of fan specified in the proposed design.
Baseline Building	Not applicable for baseline building systems 1 through 4. The curve for “Multi zone VAV with static pressure reset curve” shall be used for baseline building systems 5 through 8 and system 11.

Return/ Relief Fan Power Index
Applicability	Any system with a return fan
Definition	The return fan power per unit of flow
Units	kW/cfm
Input Restrictions	As specified in the manufacturers’ literature
Baseline Building	Applicable when the baseline building uses the power-per-unit-flow method. Fan power is determined using Table 53. This power is then multiplied by the return fan ratio.

Exhaust Fan Systems

Exhaust fans include toilet, kitchen and laboratory exhaust. Some systems typically operate at constant flow, while flow varies for other systems depending on, for instance, the position of the sash for fume hoods. Exhaust fan flow is specified and scheduled for each thermal zone. An exhaust fan system may serve multiple thermal zones. The baseline building has exhaust fans when the proposed design has exhaust fans. The design exhaust airflow is the same for the baseline building and the proposed building.

Exhaust Fan Name
Applicability	All exhaust systems serving multiple thermal zones
Definition	A unique descriptor for each exhaust fan. This should be keyed to the construction documents, if possible, to facilitate plan checking. Exhaust rates and schedules at the thermal zone level refer to this name.
Units	Text, unique
Input Restrictions	Where applicable, this should match the tags that are used on the plans
Baseline Building	The baseline building will have an exhaust system that corresponds to the proposed design. The name can be identical to that used for the proposed design or some other appropriate name may be used.

Exhaust Fan System Modeling Guide
Applicability	All exhaust fan systems
Definition	Software commonly models fans in three ways. See definition for supply system modeling method.
Units	List: Power-Per-Unit-Flow, Static Pressure, or Brake Horsepower
Input Restrictions	As designed
Baseline Building	If the proposed design uses the power-per-unit-flow method, the baseline building shall also use this method, otherwise the baseline building shall use the static pressure method

Exhaust Fan Rated Capacity
Applicability	All exhaust systems
Definition	The rated design airflow rate of the exhaust fan system. This building descriptor defines the 100% flow case for the part-flow curve. Actual airflow is the sum of the flow specified for each thermal zone, as modified by the schedule for each thermal zone.
Units	cfm
Input Restrictions	As designed
Baseline Building	Same as the proposed design except that baseline building kitchen exhaust rate may not exceed the maximum levels defined by Section 3.5.5.3 of this document

Fan Control Method
Applicability	All exhaust fan systems
Definition	A description of how the exhaust fan(s) are controlled. The options include: · Constant volume · Two-speed · Variable-flow, inlet or discharge dampers · Variable-flow, inlet guide vanes · Variable-flow, VSD · Variable-flow, variable pitch blades
Units	List (see above)
Input Restrictions	As designed, however, when exhaust fan flow at the thermal zone level is varied through a schedule, one of the variable-flow options shall be specified
Baseline Building	The baseline building exhaust fan control shall generally be the same as the proposed design. Exceptions: Exhaust fans s serving laboratory spaces shall reduce the exhaust air volume during unoccupied periods to the largest of 50% of zone peak airflow, the minimum outdoor airflow rate, or the airflow rate required to comply with applicable codes or accreditation standards as described in Section 3.5.5.3 under descriptor Laboratory: Exhaust Minimum Airflow Rate.

Exhaust Fan Schedule
Applicability	All exhaust fan systems
Definition	A schedule that indicates when the exhaust fan system is available for operation. Exhaust fan flow is specified at the thermal zone level.
Units	Data structure: schedule, on/off
Input Restrictions	As designed
Baseline Building	Same as the proposed design for exhaust fans not serving kitchen or laboratory spaces For kitchen and laboratory zone exhaust, refer to Section 3.5.5.3 of this document

Exhaust Fan Brake Horsepower
Applicability	All exhaust fan systems
Definition	The design shaft brake horsepower of the exhaust fan(s)
Units	Brake horsepower (bhp)
Input Restrictions	As designed
Baseline Building	The bhp for the baseline building is the total system fan horsepower from Table 53 of this document multiplied by the exhaust fan ratio

Exhaust Fan Design Static Pressure
Applicability	Any system with return or relief fans that uses the static pressure method
Definition	The design static pressure for exhaust fan system. This is important for both fan electric energy usage and duct heat gain calculations.
Units	Inches of water column (in. H2O)
Input Restrictions	As designed for exhaust fans not serving kitchens. The design static pressure for the exhaust fan does not need to be specified if the exhaust fan bhp is specified.
Baseline Building	The exhaust fan static pressure for the baseline building would be equal to the total fan system static pressure (specified in section Supply Fan Static Pressure) multiplied by the exhaust fan ratio Exhaust Fan Static Pressure = (Exhaust Fan BHP ´ 6356 ´ 0.65)/cfm exhaust

Exhaust Fan Efficiency
Applicability	Any exhaust fan system that uses the static pressure method
Definition	The efficiency of the exhaust fan at rated capacity; this is the static efficiency and does not include losses through the motor
Units	Unitless
Input Restrictions	As designed. The exhaust fan efficiency does not need to be specified if the return fan bhp is specified.
Baseline Building	For baseline system, fan efficiency is 65%

Exhaust Fan Motor Efficiency
Applicability	All exhaust fan systems
Definition	The full-load efficiency of the motor serving the exhaust fan
Units	Unitless
Input Restrictions	As designed
Baseline Building	From Table G3.9.1 of Standard 90.1-2019 for the next motor size greater than the bhp calculated, through the process described above, using a totally enclosed fan motor at 1800 rpm

Fan Part-Flow Power Curve
Applicability	All variable flow exhaust fan systems
Definition	A part-load power curve that represents the power draw of the exhaust fan as a function of the airflow
Units	Unitless ratio
Input Restrictions	As designed. The default fan curve shall be selected from Equation (11) and Table 57 for the type of fan specified in the proposed design.
Baseline Building	Same as proposed

Exhaust Fan Power Index
Applicability	All exhaust systems
Definition	The fan power of the exhaust fan per unit of flow. This building descriptor is applicable only with the power-per-unit-flow method.
Units	kW/cfm
Input Restrictions	As designed
Baseline Building	The fan system power from Table 53 multiplied by the exhaust fan ratio

Supply Fans

Fan System Modeling Method
Applicability	All fan systems
Definition	Software commonly models fans in three ways. Power-per-unit-flow. The simple method is for the user to enter the electric power per unit of flow (W/cfm). This method is commonly used for unitary equipment and other small fan systems. Static pressure. A more detailed method is to model the fan as a system whereby the static pressure, fan efficiency, part-load curve, and motor efficiency are specified at design conditions. Break horsepower. A third method is to specify brake horsepower at design conditions instead of fan efficiency and static pressure. This is a variation of the second method whereby brake horsepower is specified in lieu of static pressure and fan efficiency. The latter two methods are commonly used for VAV and other larger fan systems.
Units	List: power-per-unit-flow, static pressure or brake horsepower
Input Restrictions	As designed. The power-per-unit-flow method shall be used when no fan performance data is available for the proposed design cooling system, e.g. only EER or SEER are available.
Baseline Rules	If the proposed design uses the power-per-unit-flow method, the baseline building shall also use this method, otherwise the baseline building shall use the brake horsepower method.

Supply Fan Design Air Rated Capacity
Applicability	All fan systems
Definition	The design air flow rate of the supply fan(s) at design conditions. This building descriptor sets the 100% point for the fan part-load curve.
Units	cfm
Input Restrictions	As designed. This input should be at least as great as the sum of the design air flow specified for each of the thermal blocks that are served by the fan system. For multiple deck systems, a separate entry should be made for each deck.
Baseline Rules	The program shall automatically size the air flow at each thermal block to meet the loads. The design air flow rate calculation shall be based on a 20 degree temperature differential between supply air and the room air. The supply fan design air flow rate shall be the sum of the calculated design air flow for the thermal blocks served by the fan system.

Fan Control Method
Applicability	All fan systems
Definition	A description of how the supply (and return/relief) fan(s) are controlled. The options include: Constant volume Variable-flow, inlet or discharge dampers Variable-flow, inlet guide vanes Variable-flow, variable speed drive (VSD) Variable-flow, variable pitch blades Variable-flow, other Two-speed Constant volume, cycling (fan cycles with heating and cooling)
Units	List (see above)
Input Restrictions	As designed

Supply Fan Brake Horsepower
Applicability	All fan systems, except those specified using the power-per-unit-flow method
Definition	The design shaft brake horsepower of the supply fan(s). This input does not need to be supplied if the Supply Fan kW is supplied.
Units	Horsepower (hp)
Input Restrictions	As designed. If this building descriptor is specified for the proposed design, then the Static Pressure and Fan Efficiency are not.

Supply Fan Static Pressure
Applicability	All fan systems, except those specified using the power-per-unit-flow method
Definition	The design static pressure for the supply fan. This is important for both fan electric energy usage and duct heat gain calculations.
Units	Inches of water column (in. H₂0)
Input Restrictions	As designed. The design static pressure for the supply fan does not need to be specified if the supply fan brake horsepower (bhp) is specified.

Supply Fan Efficiency
Applicability	All fan systems, except those specified using the power-per-unit-flow method
Definition	The efficiency of the fan at design conditions
Units	Unitless
Input Restrictions	As designed. The supply fan efficiency does not need to be specified if the supply fan brake horsepower (bhp) is specified.

Supply Motor Efficiency
Applicability	All supply fans, except those specified using the power-per-unit-flow method
Definition	The full-load efficiency of the motor serving the supply fan
Units	Unitless
Input Restrictions	As designed. Not applicable when the power-per-unit-flow method is used.

Fan Position
Applicability	All supply fans
Definition	The position of the supply fan relative to the cooling coil. The configuration is either draw through (fan is downstream of the coil) or blow through (fan is upstream of the coil).
Units	List (see above)
Input Restrictions	As designed.

Motor Position
Applicability	All supply fans
Definition	The position of the supply fan motor relative to the cooling air stream. The choices are: in the air stream or out of the air stream.
Units	List (see above)
Input Restrictions	As designed.

Fan Part-Flow Power Curve

Applicability

All variable flow fan systems

Definition

A part-load power curve which represents the percentage full-load power draw of the supply fan as a function of the percentage full-load air flow. The curve is typically represented as a quadratic equation with an absolute minimum power draw specified.

Units

Unitless ratio

Input Restrictions

As designed. The default fan curve shall be selected from Equation (6.7.3-1) and [bookref id="fan-curve-default-values"] for the type of fan specified in the proposed design.

(6.7.3-1)

$Greater \;of$

$PLR = a + b \cdot FanRatio + c \cdot FanRatio^2 + d \cdot FanRatio^3$

$PLR = PowerMin $

where

PLR	Ratio of fan power at part load conditions to full load fan power
PowerMin	Minimum fan power
FanRatio	Ratio of cfm at part-load to full-load cfm
a, b, c and d	Constants from [bookref id="fan-curve-default-values"] below

[table title="Fan Curve Default Values" id="fan-curve-default-values"]

Fan Type - Control Type	a	b	c	d	%Power_Min
AF or BI riding the curve^a	0.1631	1.5901	-0.8817	0.1281	70%
AF or BI with inlet vanes^a	0.9977	-0.659	0.9547	-0.2936	50%
FC riding the curve^a	0.1224	0.612	0.5983	-0.3334	30%
FC with inlet vanes^a	0.3038	-0.7608	2.2729	-0.8169	30%
Vane-axial with variable pitch blades^a	0.1639	-0.4016	1.9909	-0.7541	20%
Any fan with VSD (use for baseline building)^b	0.0013	0.1470	0.9506	-0.0998	20%
VSD with static pressure reset^c	-0.0031	0.0991	1.0268	-0.1128	20%
Data Sources: a. ECB Compliance Supplement, public review draft, Version 1.2, March 1996, but adjusted to be relatively consistent with the curve specified in the PRM. b. The fan curve for VSD is specified in Table G3.1.3.15 c. Advanced VAV System Design Guide, California Energy Commission, CEC Publication 500,-03-082 A-11, April 2005, but adjusted to be relatively consistent with the curve specified in the PRM..

Supply Fan kW

Applicability

Fan systems that use the power-per-unit-flow method

Definition

The supply fan power per unit of flow.

Units

kW/cfm

Input Restrictions

As designed or specified in the manufacturers’ literature. For units with rated total cooling capacities less than 120,000 Btu/h, the user may default to a value calculated as follows:

(6.7.3-2)

$$ Fan_{kw} = 0.365 \times \frac{Q_{rated}}{30,000} $$

where

Fan_kw	The supply fan power (kW)
Q_rated	The rated total cooling capacity (Btu/h)

Relief Fans

The baseline building has a return fan when the baseline building system is type 3 through 8 and the proposed design has a return fan.

Plenum Zone
Applicability	Any system with return ducts or return air plenum
Definition	A reference to the thermal block that serves as return plenum or where the return ducts are located
Units	Text, unique
Input Restrictions	As designed

Return Air Path
Applicability	Any system with return ducts or return air plenum
Definition	Describes the return path for air. This can be one of the following: ducted return; plenum return; or direct-to-unit.
Units	List (see above)
Input Restrictions	As designed

Return/Relief Air Rated Capacity
Applicability	All systems with a return or relief fan
Definition	The design air flow fan capacity of the return or relief fan(s). This sets the 100% fan flow point for the part-load curve (see below).
Units	cfm
Input Restrictions	As designed

Return/Relief Fan Brake Horsepower
Applicability	Any system with return or relief fans that uses the brake horsepower method
Definition	The design shaft brake horsepower of the return/relief fan(s)
Units	Brake horsepower (bhp)
Input Restrictions	As designed

Return/Relief Design Static Pressure
Applicability	Any system with return or relief fans that uses the static pressure method
Definition	The design static pressure for return fan system. This is important for both fan electric energy usage and duct heat gain calculations.
Units	Inches of water column (in. H₂0)
Input Restrictions	As designed. The design static pressure for the return fan does not need to be specified if the return fan brake horsepower (bhp) is specified.

Return/Relief Fan Efficiency
Applicability	Any system with return or relief fans that uses the static pressure method
Definition	The efficiency of the fan at design conditions
Units	Unitless
Input Restrictions	As designed. The return/relief fan efficiency does not need to be specified if the return fan brake horsepower (bhp) is specified.

Return/Relief Motor Efficiency
Applicability	All return fans, except those specified using the power-per-unit-flow method
Definition	The full-load efficiency of the motor serving the supply fan
Units	Unitless
Input Restrictions	As designed. Not applicable when the power-per-unit-flow method is used.

Motor Position
Applicability	All return fans
Definition	The position of the supply fan motor relative to the cooling air stream. The choices are: in the air stream or out of the air stream.
Units	List (see above)
Input Restrictions	As designed.

Fan Part-Flow Power Curve
Applicability	All return fans for variable flow fan systems.
Definition	A part-load power curve which represents the percentage full-load power draw of the supply fan as a function of the percentage full-load air flow.
Units	Unitless ratio
Input Restrictions	As designed. The default fan curve shall be selected from Equation (6.7.3-1) and [bookref id="fan-curve-default-values"] for the type of fan specified in the proposed design.

Return/Relief Fan kW
Applicability	Any system with a return fan
Definition	The supply fan power per unit of flow
Units	kW/cfm
Input Restrictions	As specified in the manufacturers’ literature

Exhaust Fan Systems

Exhaust fans include toilet exhaust, kitchen exhaust, as well as fume hoods in laboratories and other spaces. Some systems typically operate at constant flow, while flow varies for other systems depending on, for instance, the position of the sash for fume hoods. Exhaust fan flow is specified and scheduled for each thermal block. An exhaust fan system may serve multiple thermal blocks.

Exhaust Fan Name
Applicability	All exhaust systems serving multiple thermal blocks
Definition	A unique descriptor for each exhaust fan. This should be keyed to the construction documents, if possible, to facilitate plan checking. Exhaust rates and schedules at the thermal block level refer to this name.
Units	Text, unique
Input Restrictions	Where applicable, this should match the tags that are used on the plans.

Exhaust Fan System Modeling Method
Applicability	All exhaust fan systems
Definition	Software commonly models fans in three ways. See definition for supply system modeling method.
Units	List: power-per-unit-flow, static pressure or brake horsepower
Input Restrictions	As designed

Exhaust Fan Rated Capacity
Applicability	All exhaust systems
Definition	The rated design air flow rate of the exhaust fan system. This building descriptor defines the 100% flow case for the part-flow curve. Actual air flow is the sum of the flow specified for each thermal block, as modified by the schedule for each thermal block.
Units	cfm
Input Restrictions	As designed

Fan Control Method
Applicability	All exhaust fan systems
Definition	A description of how the exhaust fan(s) are controlled. The options include: Constant volume Two-speed Variable-flow, inlet or discharge dampers Variable-flow, inlet guide vanes Variable-flow, variable speed drive (VSD) Variable-flow, variable pitch blades
Units	List (see above)
Input Restrictions	As designed, however, when exhaust fan flow at the thermal block level is varied through a schedule, one of the variable-flow options shall be specified.

Exhaust Fan Schedule
Applicability	All exhaust fan systems
Definition	A schedule that indicates when the exhaust fan system is available for operation. Exhaust fan flow is specified at the thermal block level.
Units	Data structure: schedule, on/off
Input Restrictions	The exhaust fan system shall be available during all periods when one or more thermal blocks served by the system are scheduling exhaust.

Exhaust Fan Brake Horsepower
Applicability	All exhaust fan systems
Definition	The design shaft brake horsepower of the exhaust fan(s).
Units	Brake horsepower (bhp)
Input Restrictions	As designed

Exhaust Fan Design Static Pressure
Applicability	Any system with return or relief fans that uses the static pressure method
Definition	The design static pressure for exhaust fan system. This is important for both fan electric energy usage and duct heat gain calculations.
Units	Inches of water column (in. H₂0)
Input Restrictions	As designed. The design static pressure for the exhaust fan does not need to be specified if the exhaust fan brake horsepower (bhp) is specified.

Exhaust Fan Efficiency
Applicability	Any exhaust fan system that uses the static pressure method
Definition	The efficiency of the exhaust fan at rated capacity
Units	Unitless
Input Restrictions	As designed. The exhaust fan efficiency does not need to be specified if the return fan brake horsepower (bhp) is specified.

Exhaust Fan Motor Efficiency
Applicability	All exhaust fan systems
Definition	The full-load efficiency of the motor serving the exhaust fan
Units	Unitless
Input Restrictions	As designed

Fan Part-Flow Power Curve
Applicability	All variable flow exhaust fan systems
Definition	A part-load power curve which represents the ratio full-load power draw of the exhaust fan as a function of the ratio full-load air flow.
Units	Unitless ratio
Input Restrictions	As designed. The default fan curve shall be selected from Equation (6.7.3-1) and [bookref id="fan-curve-default-values"] for the type of fan specified in the proposed design.

Exhaust Fan KW
Applicability	All exhaust systems
Definition	The fan power of the exhaust fan per unit of flow. This building descriptor is applicable only with the power-per-unit-flow method.
Units	W/cfm
Input Restrictions	As designed.

Supply Fans

Fan System Modeling Method
Applicability	All fan systems
Definition	Software commonly models fans in three ways. Power-per-unit-flow. The simple method is for the user to enter the electric power per unit of flow (W/cfm). This method is commonly used for unitary equipment and other small fan systems. Static pressure. A more detailed method is to model the fan as a system whereby the static pressure, fan efficiency, part-load curve, and motor efficiency are specified at design conditions. Break horsepower. A third method is to specify brake horsepower at design conditions instead of fan efficiency and static pressure. This is a variation of the second method whereby brake horsepower is specified in lieu of static pressure and fan efficiency. The latter two methods are commonly used for VAV and other larger fan systems.
Units	List: power-per-unit-flow, static pressure or brake horsepower
Input Restrictions	As designed. The power-per-unit-flow method shall be used when no fan performance data is available for the proposed design cooling system, e.g. only EER or SEER are available.
Baseline Rules	If the proposed design uses the power-per-unit-flow method, the baseline building shall also use this method, otherwise the baseline building shall use the brake horsepower method.

Supply Fan Design Air Rated Capacity
Applicability	All fan systems
Definition	The design air flow rate of the supply fan(s) at design conditions. This building descriptor sets the 100% point for the fan part-load curve.
Units	cfm
Input Restrictions	As designed. This input should be at least as great as the sum of the design air flow specified for each of the thermal blocks that are served by the fan system. For multiple deck systems, a separate entry should be made for each deck.
Baseline Rules	The program shall automatically size the air flow at each thermal block to meet the loads. The design air flow rate calculation shall be based on a 20 degree temperature differential between supply air and the room air. The supply fan design air flow rate shall be the sum of the calculated design air flow for the thermal blocks served by the fan system.

Fan Control Method
Applicability	All fan systems
Definition	A description of how the supply (and return/relief) fan(s) are controlled. The options include: Constant volume Variable-flow, inlet or discharge dampers Variable-flow, inlet guide vanes Variable-flow, variable speed drive (VSD) Variable-flow, variable pitch blades Variable-flow, other Two-speed Constant volume, cycling (fan cycles with heating and cooling)
Units	List (see above)
Input Restrictions	As designed

Supply Fan Brake Horsepower
Applicability	All fan systems, except those specified using the power-per-unit-flow method
Definition	The design shaft brake horsepower of the supply fan(s). This input does not need to be supplied if the Supply Fan kW is supplied.
Units	Horsepower (hp)
Input Restrictions	As designed. If this building descriptor is specified for the proposed design, then the Static Pressure and Fan Efficiency are not.

Supply Fan Static Pressure
Applicability	All fan systems, except those specified using the power-per-unit-flow method
Definition	The design static pressure for the supply fan. This is important for both fan electric energy usage and duct heat gain calculations.
Units	Inches of water column (in. H₂0)
Input Restrictions	As designed. The design static pressure for the supply fan does not need to be specified if the supply fan brake horsepower (bhp) is specified.

Supply Fan Efficiency
Applicability	All fan systems, except those specified using the power-per-unit-flow method
Definition	The efficiency of the fan at design conditions
Units	Unitless
Input Restrictions	As designed. The supply fan efficiency does not need to be specified if the supply fan brake horsepower (bhp) is specified.

Supply Motor Efficiency
Applicability	All supply fans, except those specified using the power-per-unit-flow method
Definition	The full-load efficiency of the motor serving the supply fan
Units	Unitless
Input Restrictions	As designed. Not applicable when the power-per-unit-flow method is used.

Fan Position
Applicability	All supply fans
Definition	The position of the supply fan relative to the cooling coil. The configuration is either draw through (fan is downstream of the coil) or blow through (fan is upstream of the coil).
Units	List (see above)
Input Restrictions	As designed.

Motor Position
Applicability	All supply fans
Definition	The position of the supply fan motor relative to the cooling air stream. The choices are: in the air stream or out of the air stream.
Units	List (see above)
Input Restrictions	As designed.

Fan Part-Flow Power Curve

Applicability

All variable flow fan systems

Definition

A part-load power curve which represents the percentage full-load power draw of the supply fan as a function of the percentage full-load air flow. The curve is typically represented as a quadratic equation with an absolute minimum power draw specified.

Units

Unitless ratio

Input Restrictions

As designed. The default fan curve shall be selected from Equation (6.7.3-1) and [bookref id="fan-curve-default-values"] for the type of fan specified in the proposed design.

(6.7.3-1)

$Greater \;of$

$PLR = a + b \cdot FanRatio + c \cdot FanRatio^2 + d \cdot FanRatio^3$

$PLR = PowerMin $

where

PLR	Ratio of fan power at part load conditions to full load fan power
PowerMin	Minimum fan power
FanRatio	Ratio of cfm at part-load to full-load cfm
a, b, c and d	Constants from [bookref id="fan-curve-default-values"] below

[table title="Fan Curve Default Values" id="fan-curve-default-values"]

Fan Type - Control Type	a	b	c	d	%Power_Min
AF or BI riding the curve^a	0.1631	1.5901	-0.8817	0.1281	70%
AF or BI with inlet vanes^a	0.9977	-0.659	0.9547	-0.2936	50%
FC riding the curve^a	0.1224	0.612	0.5983	-0.3334	30%
FC with inlet vanes^a	0.3038	-0.7608	2.2729	-0.8169	30%
Vane-axial with variable pitch blades^a	0.1639	-0.4016	1.9909	-0.7541	20%
Any fan with VSD (use for baseline building)^b	0.0013	0.1470	0.9506	-0.0998	20%
VSD with static pressure reset^c	-0.0031	0.0991	1.0268	-0.1128	20%
Data Sources: a. ECB Compliance Supplement, public review draft, Version 1.2, March 1996, but adjusted to be relatively consistent with the curve specified in the PRM. b. The fan curve for VSD is specified in Table G3.1.3.15 c. Advanced VAV System Design Guide, California Energy Commission, CEC Publication 500,-03-082 A-11, April 2005, but adjusted to be relatively consistent with the curve specified in the PRM..

Supply Fan kW

Applicability

Fan systems that use the power-per-unit-flow method

Definition

The supply fan power per unit of flow.

Units

kW/cfm

Input Restrictions

As designed or specified in the manufacturers’ literature. For units with rated total cooling capacities less than 120,000 Btu/h, the user may default to a value calculated as follows:

(6.7.3-2)

$$ Fan_{kw} = 0.365 \times \frac{Q_{rated}}{30,000} $$

where

Fan_kw	The supply fan power (kW)
Q_rated	The rated total cooling capacity (Btu/h)

Relief Fans

The baseline building has a return fan when the baseline building system is type 3 through 8 and the proposed design has a return fan.

Plenum Zone
Applicability	Any system with return ducts or return air plenum
Definition	A reference to the thermal block that serves as return plenum or where the return ducts are located
Units	Text, unique
Input Restrictions	As designed

Return Air Path
Applicability	Any system with return ducts or return air plenum
Definition	Describes the return path for air. This can be one of the following: ducted return; plenum return; or direct-to-unit.
Units	List (see above)
Input Restrictions	As designed

Return/Relief Air Rated Capacity
Applicability	All systems with a return or relief fan
Definition	The design air flow fan capacity of the return or relief fan(s). This sets the 100% fan flow point for the part-load curve (see below).
Units	cfm
Input Restrictions	As designed

Return/Relief Fan Brake Horsepower
Applicability	Any system with return or relief fans that uses the brake horsepower method
Definition	The design shaft brake horsepower of the return/relief fan(s)
Units	Brake horsepower (bhp)
Input Restrictions	As designed

Return/Relief Design Static Pressure
Applicability	Any system with return or relief fans that uses the static pressure method
Definition	The design static pressure for return fan system. This is important for both fan electric energy usage and duct heat gain calculations.
Units	Inches of water column (in. H₂0)
Input Restrictions	As designed. The design static pressure for the return fan does not need to be specified if the return fan brake horsepower (bhp) is specified.

Return/Relief Fan Efficiency
Applicability	Any system with return or relief fans that uses the static pressure method
Definition	The efficiency of the fan at design conditions
Units	Unitless
Input Restrictions	As designed. The return/relief fan efficiency does not need to be specified if the return fan brake horsepower (bhp) is specified.

Return/Relief Motor Efficiency
Applicability	All return fans, except those specified using the power-per-unit-flow method
Definition	The full-load efficiency of the motor serving the supply fan
Units	Unitless
Input Restrictions	As designed. Not applicable when the power-per-unit-flow method is used.

Motor Position
Applicability	All return fans
Definition	The position of the supply fan motor relative to the cooling air stream. The choices are: in the air stream or out of the air stream.
Units	List (see above)
Input Restrictions	As designed.

Fan Part-Flow Power Curve
Applicability	All return fans for variable flow fan systems.
Definition	A part-load power curve which represents the percentage full-load power draw of the supply fan as a function of the percentage full-load air flow.
Units	Unitless ratio
Input Restrictions	As designed. The default fan curve shall be selected from Equation (6.7.3-1) and [bookref id="fan-curve-default-values"] for the type of fan specified in the proposed design.

Return/Relief Fan kW
Applicability	Any system with a return fan
Definition	The supply fan power per unit of flow
Units	kW/cfm
Input Restrictions	As specified in the manufacturers’ literature

Exhaust Fan Systems

Exhaust fans include toilet exhaust, kitchen exhaust, as well as fume hoods in laboratories and other spaces. Some systems typically operate at constant flow, while flow varies for other systems depending on, for instance, the position of the sash for fume hoods. Exhaust fan flow is specified and scheduled for each thermal block. An exhaust fan system may serve multiple thermal blocks.

Exhaust Fan Name
Applicability	All exhaust systems serving multiple thermal blocks
Definition	A unique descriptor for each exhaust fan. This should be keyed to the construction documents, if possible, to facilitate plan checking. Exhaust rates and schedules at the thermal block level refer to this name.
Units	Text, unique
Input Restrictions	Where applicable, this should match the tags that are used on the plans.

Exhaust Fan System Modeling Method
Applicability	All exhaust fan systems
Definition	Software commonly models fans in three ways. See definition for supply system modeling method.
Units	List: power-per-unit-flow, static pressure or brake horsepower
Input Restrictions	As designed

Exhaust Fan Rated Capacity
Applicability	All exhaust systems
Definition	The rated design air flow rate of the exhaust fan system. This building descriptor defines the 100% flow case for the part-flow curve. Actual air flow is the sum of the flow specified for each thermal block, as modified by the schedule for each thermal block.
Units	cfm
Input Restrictions	As designed

Fan Control Method
Applicability	All exhaust fan systems
Definition	A description of how the exhaust fan(s) are controlled. The options include: Constant volume Two-speed Variable-flow, inlet or discharge dampers Variable-flow, inlet guide vanes Variable-flow, variable speed drive (VSD) Variable-flow, variable pitch blades
Units	List (see above)
Input Restrictions	As designed, however, when exhaust fan flow at the thermal block level is varied through a schedule, one of the variable-flow options shall be specified.

Exhaust Fan Schedule
Applicability	All exhaust fan systems
Definition	A schedule that indicates when the exhaust fan system is available for operation. Exhaust fan flow is specified at the thermal block level.
Units	Data structure: schedule, on/off
Input Restrictions	The exhaust fan system shall be available during all periods when one or more thermal blocks served by the system are scheduling exhaust.

Exhaust Fan Brake Horsepower
Applicability	All exhaust fan systems
Definition	The design shaft brake horsepower of the exhaust fan(s).
Units	Brake horsepower (bhp)
Input Restrictions	As designed

Exhaust Fan Design Static Pressure
Applicability	Any system with return or relief fans that uses the static pressure method
Definition	The design static pressure for exhaust fan system. This is important for both fan electric energy usage and duct heat gain calculations.
Units	Inches of water column (in. H₂0)
Input Restrictions	As designed. The design static pressure for the exhaust fan does not need to be specified if the exhaust fan brake horsepower (bhp) is specified.

Exhaust Fan Efficiency
Applicability	Any exhaust fan system that uses the static pressure method
Definition	The efficiency of the exhaust fan at rated capacity
Units	Unitless
Input Restrictions	As designed. The exhaust fan efficiency does not need to be specified if the return fan brake horsepower (bhp) is specified.

Exhaust Fan Motor Efficiency
Applicability	All exhaust fan systems
Definition	The full-load efficiency of the motor serving the exhaust fan
Units	Unitless
Input Restrictions	As designed

Fan Part-Flow Power Curve
Applicability	All variable flow exhaust fan systems
Definition	A part-load power curve which represents the ratio full-load power draw of the exhaust fan as a function of the ratio full-load air flow.
Units	Unitless ratio
Input Restrictions	As designed. The default fan curve shall be selected from Equation (6.7.3-1) and [bookref id="fan-curve-default-values"] for the type of fan specified in the proposed design.

Exhaust Fan KW
Applicability	All exhaust systems
Definition	The fan power of the exhaust fan per unit of flow. This building descriptor is applicable only with the power-per-unit-flow method.
Units	W/cfm
Input Restrictions	As designed.