# 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 cfms + A 0.0013 x cfms + 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 cfms (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 + Pfilter + Pprocess + Prelief 0.0017 x cfms + Pfilter + Pprocess + Prelief => 20,000 cfm 0.0011 x cfms + Pfilter + Pprocess + Prelief 0.0015 x cfms + Pfilter + Pprocess + Prelief 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.

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

## Supply Fans

Applicability Fan System Modeling Method All fan systems 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. List: power-per-unit-flow, static pressure or brake horsepower 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. 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.
Applicability Supply Fan Design Air Rated Capacity All fan systems 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. cfm 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. 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.
Applicability Fan Control Method All fan systems 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) List (see above) As designed 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)
Applicability Supply Fan Brake Horsepower All fan systems, except those specified using the power-per-unit-flow method 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. Horsepower (hp) As designed. If this building descriptor is specified for the proposed design, then the Static Pressure and Fan Efficiency are not. 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).
Applicability Supply Fan Static Pressure All fan systems, except those specified using the power-per-unit-flow method The design static pressure for the supply fan. This is important for both fan electric energy usage and duct heat gain calculations. Inches of water column (in. H20) 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. Not applicable. When Static Pressure and Fan Efficiency are entered for the proposed design, the baseline building shall use Brake Horsepower.
Applicability Supply Fan Efficiency All fan systems, except those specified using the power-per-unit-flow method The efficiency of the fan at design conditions Unitless As designed. The supply fan efficiency does not need to be specified if the supply fan brake horsepower (bhp) is specified. Not applicable. When Static Pressure and Fan Efficiency are entered for the proposed design, the baseline building shall use Brake Horsepower.
Applicability Supply Motor Efficiency All supply fans, except those specified using the power-per-unit-flow method The full-load efficiency of the motor serving the supply fan Unitless As designed. Not applicable when the power-per-unit-flow method is used. From Table 10.8 of ASHRAE Standard 90.1-2007 or Table 10.2 of ASHRAE Standard 90.1-2001
Applicability Fan Position All supply fans 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). List (see above) As designed. Draw through
Applicability Motor Position All supply fans 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. List (see above) As designed. 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 %PowerMin AF or BI riding the curvea 0.1631 1.5901 -0.8817 0.1281 70% AF or BI with inlet vanesa 0.9977 -0.659 0.9547 -0.2936 50% FC riding the curvea 0.1224 0.612 0.5983 -0.3334 30% FC with inlet vanesa 0.3038 -0.7608 2.2729 -0.8169 30% Vane-axial with variable pitch bladesa 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 resetc -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

 Fankw The supply fan power (kW) Qrated 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.

Applicability Plenum Zone Any system with return ducts or return air plenum A reference to the thermal block that serves as return plenum or where the return ducts are located Text, unique As designed 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.
Applicability Return Air Path Any system with return ducts or return air plenum Describes the return path for air. This can be one of the following: ducted return; plenum return; or direct-to-unit. List (see above) As designed 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.
Applicability Return/Relief Air Rated Capacity All systems with a return or relief fan 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). cfm As designed 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.
Applicability Return/Relief Fan Brake Horsepower Any system with return or relief fans that uses the brake horsepower method The design shaft brake horsepower of the return/relief fan(s) Brake horsepower (bhp) As designed 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.
Applicability Return/Relief Design Static Pressure Any system with return or relief fans that uses the static pressure method The design static pressure for return fan system. This is important for both fan electric energy usage and duct heat gain calculations. Inches of water column (in. H20) 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. Not applicable. When Static Pressure and Fan Efficiency are entered for the proposed design, the baseline building shall use Brake Horsepower.
Applicability Return/Relief Fan Efficiency Any system with return or relief fans that uses the static pressure method The efficiency of the fan at design conditions Unitless As designed. The return/relief fan efficiency does not need to be specified if the return fan brake horsepower (bhp) is specified. Not applicable. When Static Pressure and Fan Efficiency are entered for the proposed design, the baseline building shall use Brake Horsepower.
Applicability Return/Relief Motor Efficiency All return fans, except those specified using the power-per-unit-flow method The full-load efficiency of the motor serving the supply fan Unitless As designed. Not applicable when the power-per-unit-flow method is used. From Table 10.8 of ASHRAE Standard 90.1-2007 or Table 10.2 of ASHRAE Standard 90.1-2001
Applicability Motor Position All return fans 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. List (see above) As designed. In the air stream
Applicability Fan Part-Flow Power Curve All return fans for variable flow fan systems. 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. Unitless ratio 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. 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.
Applicability Return/Relief Fan kW Any system with a return fan The supply fan power per unit of flow kW/cfm As specified in the manufacturers’ literature 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.

Applicability Exhaust Fan Name All exhaust systems serving multiple thermal blocks 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. Text, unique Where applicable, this should match the tags that are used on the plans. 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.
Applicability Exhaust Fan System Modeling Method All exhaust fan systems Software commonly models fans in three ways. See definition for supply system modeling method. List: power-per-unit-flow, static pressure or brake horsepower As designed 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.
Applicability Exhaust Fan Rated Capacity All exhaust systems 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. cfm As designed Same as proposed design
Applicability Fan Control Method All exhaust fan systems 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 List (see above) 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. 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.
Applicability Exhaust Fan Schedule All exhaust fan systems A schedule that indicates when the exhaust fan system is available for operation. Exhaust fan flow is specified at the thermal block level. Data structure: schedule, on/off The exhaust fan system shall be available during all periods when one or more thermal blocks served by the system are scheduling exhaust. Same as the proposed design
Applicability Exhaust Fan Brake Horsepower All exhaust fan systems The design shaft brake horsepower of the exhaust fan(s). Brake horsepower (bhp) As designed 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.
Applicability Exhaust Fan Design Static Pressure Any system with return or relief fans that uses the static pressure method The design static pressure for exhaust fan system. This is important for both fan electric energy usage and duct heat gain calculations. Inches of water column (in. H20) 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. Not applicable. When static pressure and fan efficiency are entered for the proposed design, the baseline building shall use brake horsepower.
Applicability Exhaust Fan Efficiency Any exhaust fan system that uses the static pressure method The efficiency of the exhaust fan at rated capacity Unitless As designed. The exhaust fan efficiency does not need to be specified if the return fan brake horsepower (bhp) is specified. Not applicable. When static pressure and fan efficiency are entered for the proposed design, the baseline building shall use brake horsepower.
Applicability Exhaust Fan Motor Efficiency All exhaust fan systems The full-load efficiency of the motor serving the exhaust fan Unitless As designed From Table 10.8 of ASHRAE Standard 90.1-2007 or Table 10.2 of ASHRAE Standard 90.1-2001
Applicability Fan Part-Flow Power Curve All variable flow exhaust fan systems 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. Unitless ratio 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. 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.
Applicability Exhaust Fan KW All exhaust systems The fan power of the exhaust fan per unit of flow. This building descriptor is applicable only with the power-per-unit-flow method. W/cfm As designed. 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 cfms + A 0.0013 x cfms + 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 cfms (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.

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

## Supply Fans

Applicability Fan System Modeling Method All fan systems 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. List: power-per-unit-flow, static pressure or brake horsepower 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. 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.
Applicability Supply Fan Design Air Rated Capacity All fan systems 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. cfm 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. 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.
Applicability Fan Control Method All fan systems 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) List (see above) As designed 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)
Applicability Supply Fan Brake Horsepower All fan systems, except those specified using the power-per-unit-flow method 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. Horsepower (hp) As designed. If this building descriptor is specified for the proposed design, then the Static Pressure and Fan Efficiency are not. 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).
Applicability Supply Fan Static Pressure All fan systems, except those specified using the power-per-unit-flow method The design static pressure for the supply fan. This is important for both fan electric energy usage and duct heat gain calculations. Inches of water column (in. H20) 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. Not applicable. When Static Pressure and Fan Efficiency are entered for the proposed design, the baseline building shall use Brake Horsepower.
Applicability Supply Fan Efficiency All fan systems, except those specified using the power-per-unit-flow method The efficiency of the fan at design conditions Unitless As designed. The supply fan efficiency does not need to be specified if the supply fan brake horsepower (bhp) is specified. Not applicable. When Static Pressure and Fan Efficiency are entered for the proposed design, the baseline building shall use Brake Horsepower.
Applicability Supply Motor Efficiency All supply fans, except those specified using the power-per-unit-flow method The full-load efficiency of the motor serving the supply fan Unitless As designed. Not applicable when the power-per-unit-flow method is used. From Table 10.8 of ASHRAE Standard 90.1-2007
Applicability Fan Position All supply fans 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). List (see above) As designed. Draw through
Applicability Motor Position All supply fans 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. List (see above) As designed. 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 %PowerMin AF or BI riding the curvea 0.1631 1.5901 -0.8817 0.1281 70% AF or BI with inlet vanesa 0.9977 -0.659 0.9547 -0.2936 50% FC riding the curvea 0.1224 0.612 0.5983 -0.3334 30% FC with inlet vanesa 0.3038 -0.7608 2.2729 -0.8169 30% Vane-axial with variable pitch bladesa 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 resetc -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

 Fankw The supply fan power (kW) Qrated 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.

Applicability Plenum Zone Any system with return ducts or return air plenum A reference to the thermal block that serves as return plenum or where the return ducts are located Text, unique As designed 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.
Applicability Return Air Path Any system with return ducts or return air plenum Describes the return path for air. This can be one of the following: ducted return; plenum return; or direct-to-unit. List (see above) As designed 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.
Applicability Return/Relief Air Rated Capacity All systems with a return or relief fan 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). cfm As designed 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.
Applicability Return/Relief Fan Brake Horsepower Any system with return or relief fans that uses the brake horsepower method The design shaft brake horsepower of the return/relief fan(s) Brake horsepower (bhp) As designed 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.
Applicability Return/Relief Design Static Pressure Any system with return or relief fans that uses the static pressure method The design static pressure for return fan system. This is important for both fan electric energy usage and duct heat gain calculations. Inches of water column (in. H20) 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. Not applicable. When Static Pressure and Fan Efficiency are entered for the proposed design, the baseline building shall use Brake Horsepower.
Applicability Return/Relief Fan Efficiency Any system with return or relief fans that uses the static pressure method The efficiency of the fan at design conditions Unitless As designed. The return/relief fan efficiency does not need to be specified if the return fan brake horsepower (bhp) is specified. Not applicable. When Static Pressure and Fan Efficiency are entered for the proposed design, the baseline building shall use Brake Horsepower.
Applicability Return/Relief Motor Efficiency All return fans, except those specified using the power-per-unit-flow method The full-load efficiency of the motor serving the supply fan Unitless As designed. Not applicable when the power-per-unit-flow method is used. From Table 10.8 of ASHRAE Standard 90.1-2007
Applicability Motor Position All return fans 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. List (see above) As designed. In the air stream
Applicability Fan Part-Flow Power Curve All return fans for variable flow fan systems. 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. Unitless ratio 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. 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.
Applicability Return/Relief Fan kW Any system with a return fan The supply fan power per unit of flow kW/cfm As specified in the manufacturers’ literature 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.

Applicability Exhaust Fan Name All exhaust systems serving multiple thermal blocks 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. Text, unique Where applicable, this should match the tags that are used on the plans. 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.
Applicability Exhaust Fan System Modeling Method All exhaust fan systems Software commonly models fans in three ways. See definition for supply system modeling method. List: power-per-unit-flow, static pressure or brake horsepower As designed 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.
Applicability Exhaust Fan Rated Capacity All exhaust systems 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. cfm As designed Same as proposed design
Applicability Fan Control Method All exhaust fan systems 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 List (see above) 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. 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.
Applicability Exhaust Fan Schedule All exhaust fan systems A schedule that indicates when the exhaust fan system is available for operation. Exhaust fan flow is specified at the thermal block level. Data structure: schedule, on/off The exhaust fan system shall be available during all periods when one or more thermal blocks served by the system are scheduling exhaust. Same as the proposed design
Applicability Exhaust Fan Brake Horsepower All exhaust fan systems The design shaft brake horsepower of the exhaust fan(s). Brake horsepower (bhp) As designed 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.
Applicability Exhaust Fan Design Static Pressure Any system with return or relief fans that uses the static pressure method The design static pressure for exhaust fan system. This is important for both fan electric energy usage and duct heat gain calculations. Inches of water column (in. H20) 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. Not applicable. When static pressure and fan efficiency are entered for the proposed design, the baseline building shall use brake horsepower.
Applicability Exhaust Fan Efficiency Any exhaust fan system that uses the static pressure method The efficiency of the exhaust fan at rated capacity Unitless As designed. The exhaust fan efficiency does not need to be specified if the return fan brake horsepower (bhp) is specified. Not applicable. When static pressure and fan efficiency are entered for the proposed design, the baseline building shall use brake horsepower.
Applicability Exhaust Fan Motor Efficiency All exhaust fan systems The full-load efficiency of the motor serving the exhaust fan Unitless As designed From Table 10.8 of ASHRAE Standard 90.1-2007
Applicability Fan Part-Flow Power Curve All variable flow exhaust fan systems 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. Unitless ratio 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. 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.
Applicability Exhaust Fan KW All exhaust systems The fan power of the exhaust fan per unit of flow. This building descriptor is applicable only with the power-per-unit-flow method. W/cfm As designed. The fan system power from [bookref id="baseline-building-fan-system-–-ASHRAE-standard-90.1-2007"]
90.1-2010

## 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 cfms + A 0.0013 x cfms + 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 cfms (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.

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

## Supply Fans

Applicability Fan System Modeling Method All fan systems 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. List: power-per-unit-flow, static pressure or brake horsepower 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. 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.
Applicability Supply Fan Design Air Rated Capacity All fan systems 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. cfm 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. 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.
Applicability Fan Control Method All fan systems 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) List (see above) As designed 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.
Applicability Supply Fan Brake Horsepower All fan systems, except those specified using the power-per-unit-flow method 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. Horsepower (hp) As designed. If this building descriptor is specified for the proposed design, then the Static Pressure and Fan Efficiency are not. 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).
Applicability Supply Fan Static Pressure All fan systems, except those specified using the power-per-unit-flow method The design static pressure for the supply fan. This is important for both fan electric energy usage and duct heat gain calculations. Inches of water column (in. H20) 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. Not applicable. When Static Pressure and Fan Efficiency are entered for the proposed design, the baseline building shall use Brake Horsepower.
Applicability Supply Fan Efficiency All fan systems, except those specified using the power-per-unit-flow method The efficiency of the fan at design conditions Unitless As designed. The supply fan efficiency does not need to be specified if the supply fan brake horsepower (bhp) is specified. Not applicable. When Static Pressure and Fan Efficiency are entered for the proposed design, the baseline building shall use Brake Horsepower.
Applicability Supply Motor Efficiency All supply fans, except those specified using the power-per-unit-flow method The full-load efficiency of the motor serving the supply fan Unitless As designed. Not applicable when the power-per-unit-flow method is used. From Table 10.8 of ASHRAE Standard 90.1-2007
Applicability Fan Position All supply fans 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). List (see above) As designed. Draw through
Applicability Motor Position All supply fans 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. List (see above) As designed. 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 %PowerMin AF or BI riding the curvea 0.1631 1.5901 -0.8817 0.1281 70% AF or BI with inlet vanesa 0.9977 -0.659 0.9547 -0.2936 50% FC riding the curvea 0.1224 0.612 0.5983 -0.3334 30% FC with inlet vanesa 0.3038 -0.7608 2.2729 -0.8169 30% Vane-axial with variable pitch bladesa 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 resetc -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

 Fankw The supply fan power (kW) Qrated 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.

Applicability Plenum Zone Any system with return ducts or return air plenum A reference to the thermal block that serves as return plenum or where the return ducts are located Text, unique As designed 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.
Applicability Return Air Path Any system with return ducts or return air plenum Describes the return path for air. This can be one of the following: ducted return; plenum return; or direct-to-unit. List (see above) As designed 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.
Applicability Return/Relief Air Rated Capacity All systems with a return or relief fan 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). cfm As designed 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.
Applicability Return/Relief Fan Brake Horsepower Any system with return or relief fans that uses the brake horsepower method The design shaft brake horsepower of the return/relief fan(s) Brake horsepower (bhp) As designed 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.
Applicability Return/Relief Design Static Pressure Any system with return or relief fans that uses the static pressure method The design static pressure for return fan system. This is important for both fan electric energy usage and duct heat gain calculations. Inches of water column (in. H20) 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. Not applicable. When Static Pressure and Fan Efficiency are entered for the proposed design, the baseline building shall use Brake Horsepower.
Applicability Return/Relief Fan Efficiency Any system with return or relief fans that uses the static pressure method The efficiency of the fan at design conditions Unitless As designed. The return/relief fan efficiency does not need to be specified if the return fan brake horsepower (bhp) is specified. Not applicable. When Static Pressure and Fan Efficiency are entered for the proposed design, the baseline building shall use Brake Horsepower.
Applicability Return/Relief Motor Efficiency All return fans, except those specified using the power-per-unit-flow method The full-load efficiency of the motor serving the supply fan Unitless As designed. Not applicable when the power-per-unit-flow method is used. From Table 10.8 of ASHRAE Standard 90.1-2007
Applicability Motor Position All return fans 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. List (see above) As designed. In the air stream
Applicability Fan Part-Flow Power Curve All return fans for variable flow fan systems. 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. Unitless ratio 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. 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.
Applicability Return/Relief Fan kW Any system with a return fan The supply fan power per unit of flow kW/cfm As specified in the manufacturers’ literature 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.

Applicability Exhaust Fan Name All exhaust systems serving multiple thermal blocks 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. Text, unique Where applicable, this should match the tags that are used on the plans. 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.
Applicability Exhaust Fan System Modeling Method All exhaust fan systems Software commonly models fans in three ways. See definition for supply system modeling method. List: power-per-unit-flow, static pressure or brake horsepower As designed 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.
Applicability Exhaust Fan Rated Capacity All exhaust systems 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. cfm As designed 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.
Applicability Fan Control Method All exhaust fan systems 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 List (see above) 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. 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.
Applicability Exhaust Fan Schedule All exhaust fan systems A schedule that indicates when the exhaust fan system is available for operation. Exhaust fan flow is specified at the thermal block level. Data structure: schedule, on/off The exhaust fan system shall be available during all periods when one or more thermal blocks served by the system are scheduling exhaust. Same as the proposed design
Applicability Exhaust Fan Brake Horsepower All exhaust fan systems The design shaft brake horsepower of the exhaust fan(s). Brake horsepower (bhp) As designed The bhp for the baseline building is the total system fan horsepower from Table 6.7.3-1 times the exhaust fan ratio.
Applicability Exhaust Fan Design Static Pressure Any system with return or relief fans that uses the static pressure method The design static pressure for exhaust fan system. This is important for both fan electric energy usage and duct heat gain calculations. Inches of water column (in. H20) 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. Not applicable. When static pressure and fan efficiency are entered for the proposed design, the baseline building shall use brake horsepower.
Applicability Exhaust Fan Efficiency Any exhaust fan system that uses the static pressure method The efficiency of the exhaust fan at rated capacity Unitless As designed. The exhaust fan efficiency does not need to be specified if the return fan brake horsepower (bhp) is specified. Not applicable. When static pressure and fan efficiency are entered for the proposed design, the baseline building shall use brake horsepower.
Applicability Exhaust Fan Motor Efficiency All exhaust fan systems The full-load efficiency of the motor serving the exhaust fan Unitless As designed From Table 10.8 of ASHRAE Standard 90.1-2007
Applicability Fan Part-Flow Power Curve All variable flow exhaust fan systems 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. Unitless ratio 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. 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.
Applicability Exhaust Fan KW All exhaust systems The fan power of the exhaust fan per unit of flow. This building descriptor is applicable only with the power-per-unit-flow method. W/cfm As designed. The fan system power from Table 6.7.3-1.
90.1-2016 BM

Building EQ

## Supply Fans

Applicability Fan System Modeling Method All fan systems 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. List: power-per-unit-flow, static pressure or brake horsepower 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. 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.
Applicability Supply Fan Design Air Rated Capacity All fan systems 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. cfm 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. 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.
Applicability Fan Control Method All fan systems 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) List (see above) As designed

Applicability Supply Fan Brake Horsepower All fan systems, except those specified using the power-per-unit-flow method 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. Horsepower (hp) As designed. If this building descriptor is specified for the proposed design, then the Static Pressure and Fan Efficiency are not.
Applicability Supply Fan Static Pressure All fan systems, except those specified using the power-per-unit-flow method The design static pressure for the supply fan. This is important for both fan electric energy usage and duct heat gain calculations. Inches of water column (in. H20) 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.
Applicability Supply Fan Efficiency All fan systems, except those specified using the power-per-unit-flow method The efficiency of the fan at design conditions Unitless As designed. The supply fan efficiency does not need to be specified if the supply fan brake horsepower (bhp) is specified.
Applicability Supply Motor Efficiency All supply fans, except those specified using the power-per-unit-flow method The full-load efficiency of the motor serving the supply fan Unitless As designed. Not applicable when the power-per-unit-flow method is used.
Applicability Fan Position All supply fans 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). List (see above) As designed.
Applicability Motor Position All supply fans 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. List (see above) 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 %PowerMin AF or BI riding the curvea 0.1631 1.5901 -0.8817 0.1281 70% AF or BI with inlet vanesa 0.9977 -0.659 0.9547 -0.2936 50% FC riding the curvea 0.1224 0.612 0.5983 -0.3334 30% FC with inlet vanesa 0.3038 -0.7608 2.2729 -0.8169 30% Vane-axial with variable pitch bladesa 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 resetc -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

 Fankw The supply fan power (kW) Qrated 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.

Applicability Plenum Zone Any system with return ducts or return air plenum A reference to the thermal block that serves as return plenum or where the return ducts are located Text, unique As designed
Applicability Return Air Path Any system with return ducts or return air plenum Describes the return path for air. This can be one of the following: ducted return; plenum return; or direct-to-unit. List (see above) As designed
Applicability Return/Relief Air Rated Capacity All systems with a return or relief fan 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). cfm As designed
Applicability Return/Relief Fan Brake Horsepower Any system with return or relief fans that uses the brake horsepower method The design shaft brake horsepower of the return/relief fan(s) Brake horsepower (bhp) As designed
Applicability Return/Relief Design Static Pressure Any system with return or relief fans that uses the static pressure method The design static pressure for return fan system. This is important for both fan electric energy usage and duct heat gain calculations. Inches of water column (in. H20) 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.
Applicability Return/Relief Fan Efficiency Any system with return or relief fans that uses the static pressure method The efficiency of the fan at design conditions Unitless As designed. The return/relief fan efficiency does not need to be specified if the return fan brake horsepower (bhp) is specified.
Applicability Return/Relief Motor Efficiency All return fans, except those specified using the power-per-unit-flow method The full-load efficiency of the motor serving the supply fan Unitless As designed. Not applicable when the power-per-unit-flow method is used.
Applicability Motor Position All return fans 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. List (see above) As designed.
Applicability Fan Part-Flow Power Curve All return fans for variable flow fan systems. 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. Unitless ratio 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.
Applicability Return/Relief Fan kW Any system with a return fan The supply fan power per unit of flow kW/cfm 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.

Applicability Exhaust Fan Name All exhaust systems serving multiple thermal blocks 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. Text, unique Where applicable, this should match the tags that are used on the plans.
Applicability Exhaust Fan System Modeling Method All exhaust fan systems Software commonly models fans in three ways. See definition for supply system modeling method. List: power-per-unit-flow, static pressure or brake horsepower As designed
Applicability Exhaust Fan Rated Capacity All exhaust systems 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. cfm As designed
Applicability Fan Control Method All exhaust fan systems 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 List (see above) 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.
Applicability Exhaust Fan Schedule All exhaust fan systems A schedule that indicates when the exhaust fan system is available for operation. Exhaust fan flow is specified at the thermal block level. Data structure: schedule, on/off The exhaust fan system shall be available during all periods when one or more thermal blocks served by the system are scheduling exhaust.
Applicability Exhaust Fan Brake Horsepower All exhaust fan systems The design shaft brake horsepower of the exhaust fan(s). Brake horsepower (bhp) As designed
Applicability Exhaust Fan Design Static Pressure Any system with return or relief fans that uses the static pressure method The design static pressure for exhaust fan system. This is important for both fan electric energy usage and duct heat gain calculations. Inches of water column (in. H20) 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.
Applicability Exhaust Fan Efficiency Any exhaust fan system that uses the static pressure method The efficiency of the exhaust fan at rated capacity Unitless As designed. The exhaust fan efficiency does not need to be specified if the return fan brake horsepower (bhp) is specified.
Applicability Exhaust Fan Motor Efficiency All exhaust fan systems The full-load efficiency of the motor serving the exhaust fan Unitless As designed
Applicability Fan Part-Flow Power Curve All variable flow exhaust fan systems 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. Unitless ratio 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.
Applicability Exhaust Fan KW All exhaust systems The fan power of the exhaust fan per unit of flow. This building descriptor is applicable only with the power-per-unit-flow method. W/cfm As designed.
Energy Star

## Supply Fans

Applicability Fan System Modeling Method All fan systems 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. List: power-per-unit-flow, static pressure or brake horsepower 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. 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.
Applicability Supply Fan Design Air Rated Capacity All fan systems 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. cfm 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. 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.
Applicability Fan Control Method All fan systems 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) List (see above) As designed

Applicability Supply Fan Brake Horsepower All fan systems, except those specified using the power-per-unit-flow method 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. Horsepower (hp) As designed. If this building descriptor is specified for the proposed design, then the Static Pressure and Fan Efficiency are not.
Applicability Supply Fan Static Pressure All fan systems, except those specified using the power-per-unit-flow method The design static pressure for the supply fan. This is important for both fan electric energy usage and duct heat gain calculations. Inches of water column (in. H20) 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.
Applicability Supply Fan Efficiency All fan systems, except those specified using the power-per-unit-flow method The efficiency of the fan at design conditions Unitless As designed. The supply fan efficiency does not need to be specified if the supply fan brake horsepower (bhp) is specified.
Applicability Supply Motor Efficiency All supply fans, except those specified using the power-per-unit-flow method The full-load efficiency of the motor serving the supply fan Unitless As designed. Not applicable when the power-per-unit-flow method is used.
Applicability Fan Position All supply fans 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). List (see above) As designed.
Applicability Motor Position All supply fans 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. List (see above) 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 %PowerMin AF or BI riding the curvea 0.1631 1.5901 -0.8817 0.1281 70% AF or BI with inlet vanesa 0.9977 -0.659 0.9547 -0.2936 50% FC riding the curvea 0.1224 0.612 0.5983 -0.3334 30% FC with inlet vanesa 0.3038 -0.7608 2.2729 -0.8169 30% Vane-axial with variable pitch bladesa 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 resetc -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

 Fankw The supply fan power (kW) Qrated 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.

Applicability Plenum Zone Any system with return ducts or return air plenum A reference to the thermal block that serves as return plenum or where the return ducts are located Text, unique As designed
Applicability Return Air Path Any system with return ducts or return air plenum Describes the return path for air. This can be one of the following: ducted return; plenum return; or direct-to-unit. List (see above) As designed
Applicability Return/Relief Air Rated Capacity All systems with a return or relief fan 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). cfm As designed
Applicability Return/Relief Fan Brake Horsepower Any system with return or relief fans that uses the brake horsepower method The design shaft brake horsepower of the return/relief fan(s) Brake horsepower (bhp) As designed
Applicability Return/Relief Design Static Pressure Any system with return or relief fans that uses the static pressure method The design static pressure for return fan system. This is important for both fan electric energy usage and duct heat gain calculations. Inches of water column (in. H20) 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.
Applicability Return/Relief Fan Efficiency Any system with return or relief fans that uses the static pressure method The efficiency of the fan at design conditions Unitless As designed. The return/relief fan efficiency does not need to be specified if the return fan brake horsepower (bhp) is specified.
Applicability Return/Relief Motor Efficiency All return fans, except those specified using the power-per-unit-flow method The full-load efficiency of the motor serving the supply fan Unitless As designed. Not applicable when the power-per-unit-flow method is used.
Applicability Motor Position All return fans 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. List (see above) As designed.
Applicability Fan Part-Flow Power Curve All return fans for variable flow fan systems. 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. Unitless ratio 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.
Applicability Return/Relief Fan kW Any system with a return fan The supply fan power per unit of flow kW/cfm 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.

Applicability Exhaust Fan Name All exhaust systems serving multiple thermal blocks 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. Text, unique Where applicable, this should match the tags that are used on the plans.
Applicability Exhaust Fan System Modeling Method All exhaust fan systems Software commonly models fans in three ways. See definition for supply system modeling method. List: power-per-unit-flow, static pressure or brake horsepower As designed
Applicability Exhaust Fan Rated Capacity All exhaust systems 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. cfm As designed
Applicability Fan Control Method All exhaust fan systems 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 List (see above) 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.
Applicability Exhaust Fan Schedule All exhaust fan systems A schedule that indicates when the exhaust fan system is available for operation. Exhaust fan flow is specified at the thermal block level. Data structure: schedule, on/off The exhaust fan system shall be available during all periods when one or more thermal blocks served by the system are scheduling exhaust.
Applicability Exhaust Fan Brake Horsepower All exhaust fan systems The design shaft brake horsepower of the exhaust fan(s). Brake horsepower (bhp) As designed
Applicability Exhaust Fan Design Static Pressure Any system with return or relief fans that uses the static pressure method The design static pressure for exhaust fan system. This is important for both fan electric energy usage and duct heat gain calculations. Inches of water column (in. H20) 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.
Applicability Exhaust Fan Efficiency Any exhaust fan system that uses the static pressure method The efficiency of the exhaust fan at rated capacity Unitless As designed. The exhaust fan efficiency does not need to be specified if the return fan brake horsepower (bhp) is specified.
Applicability Exhaust Fan Motor Efficiency All exhaust fan systems The full-load efficiency of the motor serving the exhaust fan Unitless As designed
Applicability Fan Part-Flow Power Curve All variable flow exhaust fan systems 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. Unitless ratio 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.
Applicability Exhaust Fan KW All exhaust systems The fan power of the exhaust fan per unit of flow. This building descriptor is applicable only with the power-per-unit-flow method. W/cfm As designed.