3.8.5 Pumps

Baseline Building Summary. Hot water pumping in the baseline building (systems 1, 5, and 7) shall be modeled as a variable flow primary only system. When the spaces served by the hot water system are greater than or equal to 120,000 ft², the pump shall have a variable speed drive, otherwise, the pump “rides the curve”. Pumping energy shall be assumed to be 19 W/gpm. Two-way valves are assumed at the heating coils with a modulating bypass valve at the end of the loop. The bypass valve shall open as necessary to maintain minimum flow through the boiler when the system is activated. This will establish the minimum flow through the system.

Chilled water pumping in the baseline building (systems 7 and 8) is a primary/secondary system. Each chiller has its own primary and condenser water pumps that operate when the chiller is activated. All primary and secondary pumps shall be assumed to be 22 W/gpm and the condenser water pump is assumed to be 19 W/gpm. For plants less than or equal to 300 tons, the secondary pump “rides the curve” for larger plants, the pump has a variable speed drive.

General Notes. The building descriptors in this section are repeated for each pumping system. See the Pump Service building descriptor for a list of common pump services.

Pump Name
Applicability All pumps
Definition A unique descriptor for each pump
Units Text, unique
Input Restrictions User entry. Where applicable, this should match the tags that are used on the plans.
Baseline Rules Same as the proposed design. If there is no equivalent in the proposed design, assign a sequential tag to each piece of equipment. The sequential tags should indicate the pump service as part of the descriptor (e.g. CW for condenser water, CHW for chilled water, or HHW for heating hot water).
Pump Service
Applicability All pumps
Definition The service for each pump. Choices include:
  • Chilled water
  • Chilled water (primary)
  • Chilled water (secondary)
  • Heating water
  • Heating water (primary)
  • Heating water (secondary)
  • Service hot water
  • Condenser water
  • Loop water (for hydronic heat pumps)
Units List (see above)
Input Restrictions As designed
Baseline Rules As needed by the baseline building system
Number of Pumps
Applicability All pumps
Definition The number of identical pumps in service in a particular loop, e.g. the heating hot water loop, chilled water loop, or condenser water loop
Units Numeric: integer
Input Restrictions As designed
Baseline Rules There will be one heating hot water pump for each boiler, one chilled water pump, and one condenser water pump for each chiller.
Water Loop Design
Applicability All pumps
Definition The heating and cooling delivery systems can consist of a simple primary loop system, or more complicated primary/secondary loops or primary/secondary/tertiary loops.
Units List (see above)
Input Restrictions As designed
Baseline Rules Assume primary loops only for heating hot water. For chilled water loops, a primary-secondary loop design is assumed.
Pump Motor Modeling Method
Applicability All pumps
Definition Software commonly models fans in one of two ways: The simple method is for the user to enter the electric power per unit of flow (W/gpm). This method is commonly used for smaller systems. A more detailed method requires a specification of the pumping head, impeller efficiency, motor efficiency, and other inputs.
Units List: Power-Per-Unit-Flow or Detailed
Input Restrictions Either method may be used, as appropriate.
Baseline Rules Power-Per-Unit-Flow
Pump Motor Power-Per-Unit-Flow
Applicability All baseline building pumps and proposed design pumps that use the Power-Per-Unit-Flow method.
Definition The electric power of the pump divided by the flow at design conditions.
Units W/gpm
Input Restrictions As designed
Baseline Rules Prescribed to be 19 W/gpm for condenser and heating hot water pumps and 22 W/gpm for primary and secondary chilled water pumps.
Impeller Efficiency
Applicability All pumps in proposed design that use the detailed modeling method
Definition The full load efficiency of the impeller
Units Ratio
Input Restrictions As designed
Baseline Rules Not applicable
Motor Efficiency
Applicability All pumps in proposed design that use the detailed modeling method
Definition The full load efficiency of the pump motor
Units Ratio
Input Restrictions As designed
Baseline Rules Not applicable
Pump Design Head
Applicability All pumps in proposed design that use the detailed modeling method
Definition The design pressure for the pump
Units Feet of water (or feet of head)
Input Restrictions As designed
Baseline Rules Not applicable
Pump Minimum Speed
Applicability All two-speed or variable-speed pumps
Definition The minimum pump speed for a two-speed for variable-speed pump.  For two-speed pumps this is typically 0.67 or 0.5.  Note that the pump minimum speed is not necessarily the same as the minimum flow ratio, since the system head may change.
Units Ratio
Input Restrictions As designed
Baseline Rules The secondary chilled water pumps for baseline building systems 7 and 8 have variable speed drives when the size of the cooling plant is greater than 300 tons. In these cases the Pump Minimum Speed shall be 0.10.
Pump Design Flow (GPM)
Applicability All pumps
Definition The flow rate of the pump at design conditions. This is derived from the load, and the design supply and return temperatures.
Units gpm or gpm/ton for condenser and primary chilled water pumps
Input Restrictions Not a user input
Baseline Rules The temperature change on the evaporator side of the chillers is 12 F (56 F less 44 F) and this equates to a flow of 2 gpm/ton. The temperature change on the condenser side of the chillers is 10 F, which equates to a flow of 2.5 gpm/ton. The flow for secondary chilled water pumps varies with cooling demand, since there are two-way valves at the coils. The flow for primary only heating varies with demand down to the minimum required for flow through the boiler. A VSD is required for heating pumps when the service area is greater than or equal to 120,000 ft².
Pump Control Type
Applicability All pumps
Definition The type of control for the pump. Choices are:
  • Fixed speed, fixed flow
  • Fixed speed, variable flow (the default, with flow control via a valve)
  • Two-speed
  • Variable speed, variable flow
Units None
Input Restrictions As designed. The default is “Fixed Speed, Variable Flow” which models the action of a constant speed pump riding the curve against 2-way control valves.
Baseline Rules The hot water and condenser water loops shall be primary loops only. When the hot water system serves less than 120,000 ft², the hot water pump shall be modeled as a fixed speed, variable flow pump (riding the pump curve). When the hot water system serves more than 120,000 ft², the hot water pump shall be modeled as a variable speed pump on a primary loop. The chilled water pumping for systems 7 and 8 is primary/secondary with variable flow. When the chilled water system has a capacity of less than 300 tons, the secondary system pumps shall ride the pump curve.  When the chilled water system has a capacity of more than 300 tons, the secondary chilled water pumps shall be variable speed. Chilled water pumps used in the primary loop shall be fixed speed, fixed flow.  Condenser water pumps shall be modeled as fixed speed, fixed flow.
Pump Operation
Applicability All pumps
Definition The type of pump operation can be either On-Demand, Standby or Scheduled. On-Demand operation means the pumps are only pumping when their associated equipment is cycling, so chiller and condenser pumps are on when the chiller is on and the heating hot water pump operates when its associated boiler is cycling. Standby operation allows hot or chilled water to circulate through the primary loop of a primary/secondary loop system or through a reduced portion of a primary-only system, assuming the system has appropriate 3-way valves. Scheduled operation means that the pumps and their associated equipment are turned completely off according to occupancy schedules, time of year, or outside conditions. Under scheduled operation, when the systems are on they are assumed to be in On-Demand mode.
Units List (see above)
Input Restrictions As designed
Baseline Rules The baseline system pumps are assumed to operate in On-Demand mode. The chilled water and condenser pumps are tied to the chiller operation, cycling on and off with the chiller, and the heating hot water pumps are tied to the boiler operation.
Pump Part Load Curve
Applicability All pumps
Definition

A part-load power curve for the pump

(6.8.5-1)

$$ C\!I\!RC - PU\!M\!P - F\!P\!LR = a + b \times PLR + c \times PLR^2 + d \times PLR^3$$

(6.8.5-2)

$$ P_{pump} = P_{design} \times C\!I\!RC - PU\!M\!P - F\!P\!L\!R $$where

PLR Part load ratio (the ratio of operating flow rate in gpm to design flow rate in gpm)
Ppump Pump power draw at part-load conditions (W)
Pdesign Pump power draw at design conditions (W)

[table title="Default Part-Load CIRC-PUMP-FPLR Coefficients – VSD on Circulation Pump" id="default-part-load-CIRC-PUMP-FPLR-Coefficients-–-VSD-on-Circulation-Pump"]

Coefficient CIRC-PUMP-FPLR
a 0.0015303
b 0.0052081
c 1.1086242
d -0.1163556
Units Data structure
Input Restrictions As designed. Default is curve above.
Baseline Rules Use the defaults described above.
90.1-2016 BM

Baseline Building Summary

Hot Water Pumping

Hot water pumping in the baseline building (systems 1, 5, 7, and 12) shall be modeled as a variable flow primary only system. When the spaces served by the hot water system are greater than or equal to 120,000 ft², the pump shall have a variable speed drive, otherwise, the pump “rides the curve”. Pumping energy shall be assumed to be 19 W/gpm. Two-way valves are assumed at the heating coils with a modulating bypass valve at the end of the loop. The bypass valve shall open as necessary to maintain minimum flow through the boiler when the system is activated. This will establish the minimum flow through the system.

Chilled-water systems shall be modeled as primary/secondary systems with constant flow primary loop and variable flow secondary loop.

  • For systems with cooling capacity of 300 tons or more, the secondary pump shall be modeled with variable speed drives and a minimum flow of 25% of the design flow rate.
  • For systems with less than 300 tons cooling capacity, the secondary pump shall be modeled as riding the pump curve.

Chilled Water Pumping

Chilled-water systems shall be modeled as primary/secondary systems with constant flow primary loop and variable flow secondary loop.

  • For systems with cooling capacity of 300 tons or more, the secondary pump shall be modeled with variable speed drives and a minimum flow of 25% of the design flow rate.
  • For systems with less than 300 tons cooling capacity, the secondary pump shall be modeled as riding the pump curve.

The baseline building constant-volume primary pump power shall be modeled as 9 W/gpm, and the variable-flow secondary pump power shall be modeled as 13 W/gpm at design conditions. For computer room systems using System 11 with an integrated water-side economizer, the baseline building design primary chilled-water pump power shall be increased by 3 W/gpm for flow associated with the water-side economizer. For systems using purchased chilled water, the building distribution pump shall be modeled with variable-speed drive, a minimum flow of 25% of the design flow rate, and a pump power of 16 W/gpm.

General Notes. The building descriptors in this section are repeated for each pumping system. See the Pump Service building descriptor for a list of common pump services.

 

Pump Name

Applicability

All pumps

Definition

A unique descriptor for each pump

Units

Text, unique

Input Restrictions

User entry. Where applicable, this should match the tags that are used on the plans.

Baseline Rules

Same as the proposed design. If there is no equivalent in the proposed design, assign a sequential tag to each piece of equipment. The sequential tags should indicate the pump service as part of the descriptor (e.g. CW for condenser water, CHW for chilled water, or HHW for heating hot water).

 

Pump Service

Applicability

All pumps

Definition

The service for each pump. Choices include:

  • Chilled water
  • Chilled water (primary)
  • Chilled water (secondary)
  • Heating water
  • Heating water (primary)
  • Heating water (secondary)
  • Service hot water
  • Condenser water
  • Loop water (for hydronic heat pumps)

Units

List (see above)

Input Restrictions

As designed

Baseline Rules

As needed by the baseline building system

 

Number of Pumps

Applicability

All pumps

Definition

The number of identical pumps in service in a particular loop, e.g. the heating hot water loop, chilled water loop, or condenser water loop

Units

Numeric: integer

Input Restrictions

As designed

Baseline Rules

The number of pumps will be defined as specified below:

  • One heating hot water pump for each boiler
  • One primary chilled water pump for each chiller and one secondary chilled water pump for the chilled water loop
  • One condenser water pump for each chiller
  • One district hot water pump for each building served by a district hot water system
  • One district chilled water pump for each building served by a district chilled water system

 

Water Loop Design

Applicability

All pumps

Definition

The heating and cooling delivery systems can consist of a simple primary loop system, or more complicated primary/secondary loops or primary/secondary/tertiary loops.

Units

List (see above)

Input Restrictions

As designed

Baseline Rules

Heating water systems shall be modeled with primary loops only. Chilled water systems shall be modeled with primary/secondary loops.

 

Pump Motor Modeling Method

Applicability

All pumps

Definition

Software commonly models pumps in one of two ways: The simple method is for the user to enter the electric power per unit of flow (W/gpm). This method is commonly used for smaller systems. A more detailed method requires a specification of the pumping head, impeller efficiency, motor efficiency, and other inputs.

Units

List: Power-Per-Unit-Flow or Detailed

Input Restrictions

Either method may be used, as appropriate.

Baseline Rules

Detailed

 

Pump Motor Power-Per-Unit-Flow

Applicability

All baseline building pumps and proposed design pumps that use the Power-Per-Unit-Flow method.

Definition

The electric power of the pump divided by the flow at design conditions.

Units

W/gpm

Input Restrictions

As designed

Baseline Rules

Not applicable

 

Pump Motor Horspower

Applicability

All pumps that use the detailed modeling method

Definition

The nameplate motor horspower

Units

Horsepower

Input Restrictions

Constrained to be a value from the following list of standard motor sizes:

A standard motor size table (hp) is defined as: 1/12, 1/8, ¼, ½, ¾, 1, 1.5, 2, 3, 5, 7.5, 10, 15, 20, 25, 30, 40, 50, 60, 75, 100, 125, 150, 200

Baseline Rules

Not applicable

 

Pump Design Head

Applicability

All baseline building pumps and proposed design pumps that use the detailed modeling method

Definition

The head of the pump at design flow conditions

Units

ft or wg

Input Restrictions

As designed

Baseline Rules

For the baseline building:

  • District chilled water: 55 ft
  • District hot water: 44 ft
  • Chilled water system: baseline system pumppower is 9 W/gpm for the primary loop and 13 W/gpm for the secondary loop and this 31 ft of head for the primary loop and 44 ft of head for the secondary loop
  • Condenser water system: 60 ft
  • Hot water system: 60 ft

 

Impeller Efficiency

Applicability

All pumps in baseline building and proposed design that use the detailed modeling method

Definition

The full load efficiency of the impeller

Units

Ratio between 0 and 1.0

Input Restrictions

As designed

Baseline Rules

For the baseline building:

  • District chilled water system: 72% (assuming motor efficiency of 90% and a total pump efficiency of 65%)
  • District hot water system: 66.67% (assuming motor efficiency of 90% and a total pump efficiency of 60%)
  • Chilled water system: 72% (assuming motor efficiency of 90% and total pump efficiency of 65%)
  • Condenser water system: 66.67% (assuming motor efficiency of 90% and total pump efficiency of 60%)
  • Hot water system: 66.67% (assuming motor efficiency of 90% and total pump efficiency of 60%)

 

Motor Efficiency

Applicability

All pumps in baseline building and proposed design that use the detailed modeling method

Definition

The full load efficiency of the pump motor

Units

Ratio between 0 and 1.0

Input Restrictions

As designed

Baseline Rules

For the baseline building

  • District chilled water system: 90%
  • District hot water system: 90%
  • Chilled water system: 90%
  • Condenser water system: Motor efficiency = 90%
  • Hot water system: 90%

 

Pump Minimum Speed

Applicability

All two-speed or variable-speed pumps

Definition

The minimum pump speed for a two-speed for variable-speed pump.  For two-speed pumps this is typically 0.67 or 0.5.  Note that the pump minimum speed is not necessarily the same as the minimum flow ratio, since the system head may change.

(Equation 3.8.5-1)

$$Pump \  Speed_{Min} =  Pump \  Speed_{Design} \times \sqrt{\frac{Head_{Min}}{Head_{Design}}}$$

Units

Ratio between 0 and 1.0

Input Restrictions

As designed

Baseline Rules

When the baseline pumps are required to have variable speed drives in accordance with descriptor Pump Control Type, the pump minimum speed shall be 0.10.

 

Pump Design Flow (GPM)

Applicability

All pumps

Definition

The flow rate of the pump at design conditions. For the baseline, this is derived from the heating and cooling loads, the appropriate oversizing factors, and the design supply and return temperatures.

Units

gpm or gpm/ton for condenser and primary chilled water pumps

Input Restrictions

Not a user input

Baseline Rules

The temperature change on the evaporator side of the chillers is 12°F (56°F less 44°F) and this equates to a flow of 2 gpm/ton. The temperature change on the condenser side of the chillers is 10 °F, which equates to a flow of 2.4 gpm/ton. The flow for secondary chilled water pumps varies with cooling demand, since there are two-way valves at the coils. The flow for primary only heating varies with demand down to the minimum required for flow through the boiler. A VSD is required for heating pumps when the service area is greater than or equal to 120,000 ft². For hot water pumps servicing boilers, the flow rate in gpm shall be the boiler capacity in Btu/h / 25,000, which corresponds to a loop temperature drop of 50°F.

 

Pump Control Type

Applicability

All pumps

Definition

The type of control for the pump. Choices are:

  • Fixed speed, fixed flow
  • Fixed speed, variable flow (the default, with flow control via a valve)
  • Two-speed
  • Variable speed, variable flow

Units

None

Input Restrictions

As designed. The default is “Fixed Speed, Variable Flow” which models the action of a constant speed pump riding the curve against two-way control valves.

Baseline Rules

The following rules shall apply:

  • Hot water: Hot water loops are primary loops only. For systems serving less than 120,000 ft², the HW pump is modeled as variable flow with a constant speed pump riding the pump curve. For systems serving more than 120,000 ft², the HW pump is modeled as a variable flow with a variable speed pump controlled with a variable speed drive.
  • Condenser water pumps: Condenser water loops are primary only. CW pumps are required to be modeled as fixed speed and fixed flow.
  • Chilled water pumps:  The CHW pumping for systems 7, 8, 11, 12, and 13 are primary/secondary with variable flow. The chilled water pumps used for the primary loop are fixed speed and fixed flow. For systems with a capacity of less than 300 tons, the secondary system pumps shall ride the pump curve. For systems with a capacity greater than 300 tons, the secondary pumps will be modeled as variable speed.
  • District chilled water pump shall follow the same rules for secondary chilled water pumps.

 

Pump Operation

Applicability

All pumps

Definition

The type of pump operation can be either On-Demand, Standby or Scheduled. On-Demand operation means the pumps are only pumping when their associated equipment is cycling, so chiller and condenser pumps are on when the chiller is on and the heating hot water pump operates when its associated boiler is cycling. Standby operation allows hot or chilled water to circulate through the primary loop of a primary/secondary loop system or through a reduced portion of a primary-only system, assuming the system has appropriate 3-way valves. Scheduled operation means that the pumps and their associated equipment are turned completely off according to occupancy schedules, time of year, or outside conditions. Under scheduled operation, when the systems are on they are assumed to be in On-Demand mode.

Units

List (see above)

Input Restrictions

As designed

Baseline Rules

The baseline system pumps are assumed to operate in on-demand mode. The chilled water and condenser pumps are tied to the chiller operation, cycling on and off with the chiller, and the heating hot water pumps are tied to the boiler operation.

 

Pump Part Load Curve

Applicability

All pumps

Definition

A part-load power curve for the pump

(Equation 3.8.5-2)

$$CIRC\_PUMP\_FPLR = a + b \cdot PLR + c \cdot PLR^{2} + d \cdot PLR^{3}$$

(Equation 3.8.5-3)

$$P_{Pump} = P_{Design} \times CIRC\_PUMP\_FPLR $$

Where

PLR

Part load ratio (the ratio of operating flow rate in gpm to design flow rate in gpm)

Ppump

Pump power draw at part-load conditions (W)

Pdesign

Pump power draw at design conditions (W)

a, b, c, d

Default coefficients from Appendix H

Units

Data structure

Input Restrictions

As designed. Default is curve above.

Baseline Rules

Use the defaults described above based on pump type. The curve with differential pressure reset isn’t used for the baseline building.

Building EQ

General Notes. The building descriptors in this section are repeated for each pumping system. See the Pump Service building descriptor for a list of common pump services.

Pump Name
Applicability All pumps
Definition A unique descriptor for each pump
Units Text, unique
Input Restrictions User entry. Where applicable, this should match the tags that are used on the plans.
Pump Service
Applicability All pumps
Definition The service for each pump. Choices include:
  • Chilled water
  • Chilled water (primary)
  • Chilled water (secondary)
  • Heating water
  • Heating water (primary)
  • Heating water (secondary)
  • Service hot water
  • Condenser water
  • Loop water (for hydronic heat pumps)
Units List (see above)
Input Restrictions As designed
Number of Pumps
Applicability All pumps
Definition The number of identical pumps in service in a particular loop, e.g. the heating hot water loop, chilled water loop, or condenser water loop
Units Numeric: integer
Input Restrictions As designed
Water Loop Design
Applicability All pumps
Definition The heating and cooling delivery systems can consist of a simple primary loop system, or more complicated primary/secondary loops or primary/secondary/tertiary loops.
Units List (see above)
Input Restrictions As designed
Pump Motor Modeling Method
Applicability All pumps
Definition Software commonly models fans in one of two ways: The simple method is for the user to enter the electric power per unit of flow (W/gpm). This method is commonly used for smaller systems. A more detailed method requires a specification of the
Units List: Power-Per-Unit-Flow or Detailed
Input Restrictions Either method may be used, as appropriate.
Pump Motor Power-Per-Unit-Flow
Applicability All baseline building pumps and proposed design pumps that use the Power-Per-Unit-Flow method.
Definition The electric power of the pump divided by the flow at design conditions.
Units W/gpm
Input Restrictions As designed
Impeller Efficiency
Applicability All pumps in proposed design that use the detailed modeling method
Definition The full load efficiency of the impeller
Units Ratio
Input Restrictions As designed
Motor Efficiency
Applicability All pumps in proposed design that use the detailed modeling method
Definition The full load efficiency of the pump motor
Units Ratio
Input Restrictions As designed
Pump Design Head
Applicability All pumps in proposed design that use the detailed modeling method
Definition The design pressure for the pump
Units Feet of water (or feet of head)
Input Restrictions As designed
Pump Minimum Speed
Applicability All two-speed or variable-speed pumps
Definition The minimum pump speed for a two-speed for variable-speed pump.  For two-speed pumps this is typically 0.67 or 0.5.  Note that the pump minimum speed is not necessarily the same as the minimum flow ratio, since the system head may change.
Units Ratio
Input Restrictions As designed
Pump Design Flow (GPM)
Applicability All pumps
Definition The flow rate of the pump at design conditions. This is derived from the load, and the design supply and return temperatures.
Units gpm or gpm/ton for condenser and primary chilled water pumps
Input Restrictions Not a user input
Pump Control Type
Applicability All pumps
Definition The type of control for the pump. Choices are:
  • Fixed speed, fixed flow
  • Fixed speed, variable flow (the default, with flow control via a valve)
  • Two-speed
  • Variable speed, variable flow
Units None
Input Restrictions As designed. The default is “Fixed Speed, Variable Flow” which models the action of a constant speed pump riding the curve against 2-way control valves.
Pump Operation
Applicability All pumps
Definition The type of pump operation can be either On-Demand, Standby or Scheduled. On-Demand operation means the pumps are only pumping when their associated equipment is cycling, so chiller and condenser pumps are on when the chiller is on and the heating hot water pump operates when its associated boiler is cycling. Standby operation allows hot or chilled water to circulate through the primary loop of a primary/secondary loop system or through a reduced portion of a primary-only system, assuming the system has appropriate 3-way valves. Scheduled operation means that the pumps and their associated equipment are turned completely off according to occupancy schedules, time of year, or outside conditions. Under scheduled operation, when the systems are on they are assumed to be in On-Demand mode.
Units List (see above)
Input Restrictions As designed
Pump Part Load Curve
Applicability All pumps
Definition

A part-load power curve for the pump

(6.8.5-1)

$$ C\!I\!RC - PU\!M\!P - F\!P\!LR = a + b \times PLR + c \times PLR^2 + d \times PLR^3$$

(6.8.5-2)

$$ P_{pump} = P_{design} \times C\!I\!RC - PU\!M\!P - F\!P\!L\!R $$where

PLR Part load ratio (the ratio of operating flow rate in gpm to design flow rate in gpm)
Ppump Pump power draw at part-load conditions (W)
Pdesign Pump power draw at design conditions (W)

[table title="Default Part-Load CIRC-PUMP-FPLR Coefficients – VSD on Circulation Pump" id="default-part-load-CIRC-PUMP-FPLR-Coefficients-–-VSD-on-Circulation-Pump"]

Coefficient CIRC-PUMP-FPLR
a 0.0015303
b 0.0052081
c 1.1086242
d -0.1163556
Units Data structure
Input Restrictions As designed. Default is curve above.
Energy Star

General Notes. The building descriptors in this section are repeated for each pumping system. See the Pump Service building descriptor for a list of common pump services.

Pump Name
Applicability All pumps
Definition A unique descriptor for each pump
Units Text, unique
Input Restrictions User entry. Where applicable, this should match the tags that are used on the plans.
Pump Service
Applicability All pumps
Definition The service for each pump. Choices include:
  • Chilled water
  • Chilled water (primary)
  • Chilled water (secondary)
  • Heating water
  • Heating water (primary)
  • Heating water (secondary)
  • Service hot water
  • Condenser water
  • Loop water (for hydronic heat pumps)
Units List (see above)
Input Restrictions As designed
Number of Pumps
Applicability All pumps
Definition The number of identical pumps in service in a particular loop, e.g. the heating hot water loop, chilled water loop, or condenser water loop
Units Numeric: integer
Input Restrictions As designed
Water Loop Design
Applicability All pumps
Definition The heating and cooling delivery systems can consist of a simple primary loop system, or more complicated primary/secondary loops or primary/secondary/tertiary loops.
Units List (see above)
Input Restrictions As designed
Pump Motor Modeling Method
Applicability All pumps
Definition Software commonly models fans in one of two ways: The simple method is for the user to enter the electric power per unit of flow (W/gpm). This method is commonly used for smaller systems. A more detailed method requires a specification of the
Units List: Power-Per-Unit-Flow or Detailed
Input Restrictions Either method may be used, as appropriate.
Pump Motor Power-Per-Unit-Flow
Applicability All baseline building pumps and proposed design pumps that use the Power-Per-Unit-Flow method.
Definition The electric power of the pump divided by the flow at design conditions.
Units W/gpm
Input Restrictions As designed
Impeller Efficiency
Applicability All pumps in proposed design that use the detailed modeling method
Definition The full load efficiency of the impeller
Units Ratio
Input Restrictions As designed
Motor Efficiency
Applicability All pumps in proposed design that use the detailed modeling method
Definition The full load efficiency of the pump motor
Units Ratio
Input Restrictions As designed
Pump Design Head
Applicability All pumps in proposed design that use the detailed modeling method
Definition The design pressure for the pump
Units Feet of water (or feet of head)
Input Restrictions As designed
Pump Minimum Speed
Applicability All two-speed or variable-speed pumps
Definition The minimum pump speed for a two-speed for variable-speed pump.  For two-speed pumps this is typically 0.67 or 0.5.  Note that the pump minimum speed is not necessarily the same as the minimum flow ratio, since the system head may change.
Units Ratio
Input Restrictions As designed
Pump Design Flow (GPM)
Applicability All pumps
Definition The flow rate of the pump at design conditions. This is derived from the load, and the design supply and return temperatures.
Units gpm or gpm/ton for condenser and primary chilled water pumps
Input Restrictions Not a user input
Pump Control Type
Applicability All pumps
Definition The type of control for the pump. Choices are:
  • Fixed speed, fixed flow
  • Fixed speed, variable flow (the default, with flow control via a valve)
  • Two-speed
  • Variable speed, variable flow
Units None
Input Restrictions As designed. The default is “Fixed Speed, Variable Flow” which models the action of a constant speed pump riding the curve against 2-way control valves.
Pump Operation
Applicability All pumps
Definition The type of pump operation can be either On-Demand, Standby or Scheduled. On-Demand operation means the pumps are only pumping when their associated equipment is cycling, so chiller and condenser pumps are on when the chiller is on and the heating hot water pump operates when its associated boiler is cycling. Standby operation allows hot or chilled water to circulate through the primary loop of a primary/secondary loop system or through a reduced portion of a primary-only system, assuming the system has appropriate 3-way valves. Scheduled operation means that the pumps and their associated equipment are turned completely off according to occupancy schedules, time of year, or outside conditions. Under scheduled operation, when the systems are on they are assumed to be in On-Demand mode.
Units List (see above)
Input Restrictions As designed
Pump Part Load Curve
Applicability All pumps
Definition

A part-load power curve for the pump

(6.8.5-1)

$$ C\!I\!RC - PU\!M\!P - F\!P\!LR = a + b \times PLR + c \times PLR^2 + d \times PLR^3$$

(6.8.5-2)

$$ P_{pump} = P_{design} \times C\!I\!RC - PU\!M\!P - F\!P\!L\!R $$where

PLR Part load ratio (the ratio of operating flow rate in gpm to design flow rate in gpm)
Ppump Pump power draw at part-load conditions (W)
Pdesign Pump power draw at design conditions (W)

[table title="Default Part-Load CIRC-PUMP-FPLR Coefficients – VSD on Circulation Pump" id="default-part-load-CIRC-PUMP-FPLR-Coefficients-–-VSD-on-Circulation-Pump"]

Coefficient CIRC-PUMP-FPLR
a 0.0015303
b 0.0052081
c 1.1086242
d -0.1163556
Units Data structure
Input Restrictions As designed. Default is curve above.