# 3.7.6 Heating Systems

## General

Applicability Heating Source All systems that provide heating The source of heating for the heating and preheat coils. The choices are: Hot water Steam Electric resistance Electric heat pump Gas furnace Gas heat pump (optional feature) Oil furnace Heat recovery (for preheat coils in proposed designs) List (see above) As designed Based on the prescribed system type. Refer to the HVAC System Map in [bookref id="hvac-mapping"].

[table title="Heating Source for Baseline Building" id="heating-source-for-baseline-building"]

 Baseline Building System Heating Source System 1 – PTAC Gas Furnace System 2 – PTHP Heat pump System 3 – PSZ-AC Gas or Oil Furnace System 4 – PSZ-HP Heat pump System 5 – Packaged VAV with Reheat Hot water System 6 – Packaged VAV with PFP boxes Electric Resistance System 7 – VAV with Reheat Hot water System 8 – VAV with PFP boxes Electric Resistance

## Preheat Coil

Applicability Preheat Coil Capacity Systems with a preheat coil located in the outside air stream The heating capacity of a preheating coil at design conditions. Btu/h As designed If the proposed design has a preheat coil and it can be modeled in the baseline building system, then the baseline building also has a preheat coil sized to meet the preheat coil temperature specified for the proposed design. Autosize to maintain the preheat coil temperature of the proposed design.

## Heating Coils

Systems with boilers have heating coils, including baseline building systems 1, 5 and 7.

Applicability Heating Coil Capacity All systems with a heating coil The heating capacity of a heating coil at ARI conditions Btu/h As designed. Adjust the capacity if the number of unmet load hours exceeds 300. Autosize with a heating oversizing factor of 25%. If the number of unmet load hours for the proposed design exceeds the number of unmet load hours for the baseline building by more than 50, reduce the heating coil capacity as indicated in [bookref id="procedure-for-adjusting-equipment-hvac-sizes-in-the-baseline-building"].

## Furnace

Applicability Furnace Capacity Systems with a furnace The full load heating capacity of the unit Btu/h As designed. Adjust the capacity if the number of unmet load hours exceeds 300. Autosize with an oversizing factor of 25% (let the software determine heating capacity based on the building loads). If the number of unmet load hours for the proposed design exceeds the number of unmet load hours for the baseline building by more than 50, reduce the furnace capacity as indicated 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"].
Furnace Fuel Heating Efficiency
Applicability Systems with a furnace
Definition The full load thermal efficiency of either a gas or oil furnace at design conditions. The software must accommodate input in either Thermal Efficiency (Et) or Annual Fuel Utilization Efficiency (AFUE). Where AFUE is provided, Et shall be calculated as follows:

(6.7.6-1)

$1) All\ Single\ Package\ Equipment$
$E_t = 0.005163 \times AFUE + 0.4033$
$2) Split\ Systems, AFUE \leq 83.5$
$E_t = 0.002907 \times AFUE + 0.5787$
$3) Split\ Systems, AFUE \textgreater 83.5$
$E_t = 0.011116 \times AFUE - 0.098185$

where

 AFUE The annual fuel utilization efficiency (%) Et The thermal efficiency (fraction)
Units Fraction
Input Restrictions As designed
Baseline Rules Look up the requirement from the equipment efficiency tables in Table 6.8.1E of Standard 90.1-2007 Table 6.2.1E of Standard 90.1-2001. Use the heating input of the proposed design system to determine the size category.
Furnace Fuel Heating Part Load Efficiency Curve
Applicability Systems with furnaces
Definition An adjustment factor that represents the percentage of full load fuel consumption as a function of the percentage full load capacity. This curve shall take the form of a quadratic equation as follows:

(6.7.6-2)

$$Fuel_{partload} = Fuel_{rated} \times F\!HeatP\!LC$$

(6.7.6-3)

$$F\!HeatP\!LC = \left ( a + b \times \frac{Q_{partload}}{Q_{rated}} + c \times \left( \frac{Q_{partload}}{Q_{rated}} \right )^2 \right )$$

where

 FHeatPLC The Fuel Heating Part Load Efficiency Curve Fuelpartload The fuel consumption at part load conditions (Btu/h) Fuelrated The fuel consumption at full load (Btu/h) Qpartload The capacity at part load conditions (Btu/h) Qrated The capacity at rated conditions (Btu/h)

[table title="Furnace Efficiency Curve Coefficients" id="furnace-efficiency-curve-coefficients"]

 Coefficient Furnace a 0.0186100 b 1.0942090 c -0.1128190
Units Data structure
Input Restrictions As designed when data is available, otherwise use the default values are provided above.
Baseline Rules Use defaults
Applicability Furnace Fuel Heating Pilot Systems that use a furnace for heating The fuel input for a pilot light on a furnace Btu/h As designed Zero (pilotless ignition)
Applicability Furnace Fuel Heating Fan/Auxiliary Systems that use a furnace for heating The fan energy in forced draft furnaces and the auxiliary (pumps and outdoor fan) energy in fuel-fired heat pumps Kilowatts (kW) As designed Not applicable

## Electric Heat Pump

Applicability Electric Heat Pump Heating Capacity All heat pumps The full load heating capacity of the unit, excluding supplemental heating capacity at ARI rated conditions Btu/h As designed Autosize and use an oversizing factor of 25% (let the software determine heating capacity based on the building loads). The autosized equipment may need to be downsized to achieve a maximum difference in unmet load hours between the proposed design and the baseline building of 50.
Applicability Electric Heat Pump Supplemental Heating Source All heat pumps The auxiliary heating source for a heat pump heating system. The common control sequence is to lock out the heat pump compressor when the supplemental heat is activated. Other building descriptors may be needed if this is not the case. Choices for supplemental heat include: Electric resistance Gas furnace Oil furnace Hot water Other List (see above) As designed Electric resistance
Electric Heat Pump Heating Efficiency
Applicability All heat pumps
Definition

The heating efficiency of a heat pump at ARI rated conditions as a dimensionless ratio of output over input. The software must accommodate user input in terms of either the Coefficient of Performance (COP) or the Heating Season Performance Factor (HSPF). Where HSPF is provided, COP shall be calculated as follows:

(6.7.6-4)

$1) All\ Single\ Package\ Equipment$
$C\!O\!P = 0.2778 \times H\!S\!P\!F + 0.9667$
$2) All\ Split\ Systems$
$C\!O\!P = 0.4813 \times H\!S\!P\!F - 0.2606$

For all unitary and applied equipment where the fan energy is part of the equipment efficiency rating, the COP shall be adjusted as follows to remove the fan energy:

(6.7.6-5)

$$C\!O\!P_{adj} = \frac{\frac{H\!C\!A\!P_{rated}}{3.413} - B\!H\!P_{supply} \times 0.7457}{\frac{H\!C\!A\!P_{rated}}{C\!O\!P \times 3.413} - B\!H\!P_{supply} \times 0.7457}$$

where

 COPadj The adjusted coefficient of performance for simulation purposes COP The ARI rated coefficient of performance HCAPrated The ARI rated heating capacity of a packaged unit (kBtu/h) BHPsupply The supply fan brake horsepower (bhp).

Refer to building descriptor Supply Fan BHP.

Units Unitless
Input Restrictions As designed
Baseline Rules For the purpose of green building ratings, look up the requirement from the equipment efficiency Table 6.8.1B and Table 6.8.1D in ASHRAE Standard 90.1-2007. For the purpose of tax deduction calculations, find the equipment efficiency from Table 6.2.1B and 6.2.1D in ASHRAE Standard 90.1-2001. Use the heating capacity of the proposed design to determine the size category.
Electric Heat Pump Heating Capacity Adjustment Curve(s)
Applicability All heat pumps
Definition

A curve or group of curves that represent the available heat-pump heating capacity as a function of evaporator and condenser conditions. The default curves are given as follows:

(6.7.6-6)

$$Q_{available} = C\!A\!P\_FT \times Q_{rated}$$For air-cooled heat pumps:

(6.7.6-7)

$$C\!A\!P\_FT = a + b \times t_{odb} + c \times \left. t_{odb}\right. ^2 + d \times \left. t_{odb}\right. ^3$$

For water-cooled heat pumps:

(6.7.6-8)

$$C\!A\!P\_FT = a + b \times t_{db} + d \times t_{wt}$$

where

 Qavailable Available heating capacity at present evaporator and condenser conditions (kBtu/h) tdb The entering coil dry-bulb temperature (°F) twt The water supply temperature (°F) todb The outside-air dry-bulb temperature (°F) Qrated Rated capacity at ARI conditions (in kBtu/h

 Coefficient Water-Source Air-Source a 0.4886534 0.2536714 b -0.0067774 0.0104351 c N/A 0.0001861 d 0.0140823 -0.0000015
Units Data structure
Input Restrictions User may input curves or use default curves. If defaults are overridden, supporting documentation shall be provided.
Baseline Rules Use default curves.
Electric Heat Pump Heating Efficiency Adjustment Curve(s)
Applicability All heat pumps
Definition

A curve or group of curves that varies the heat-pump heating efficiency as a function of evaporator conditions, condenser conditions and part-load ratio. The default curves are given as follows:

(6.7.6-9)

$$P\!LR = \frac{Q_{operating}}{Q_{available}\left ( t_{db},t_{odb/wt}\right )}$$

(6.7.6-10)

$$E\!I\!R\_F\!P\!LR = a + b \times P\!LR + c \times P\!LR^2 + d \times P\!LR^3$$

Air Source Heat Pumps:

(6.7.6-11)

$$E\!I\!R\_FT = a + b \times \left ( \frac{t_{odb}}{t_{db}} \right ) + c \times \left ( \frac{t_{odb}}{t_{db}} \right ) ^2 + d \times \left ( \frac{t_{odb}}{t_{db}} \right )^3$$Water Source Heat Pumps:

(6.7.6-12)

$$E\!I\!R\_FT = a + b \times t_{wt} + d \times t_{db}$$

(6.7.6-13)

$$P_{operating} = P_{rated} \times E\!I\!R\_F\!P\!LR \times E\!I\!R\_FT \times C\!AP\_FT$$

where

 PLR Part load ratio based on available capacity (not rated capacity) EIR-FPLR A multiplier on the EIR of the heat pump as a function of part load ratio EIR-FT A multiplier on the EIR of the heat pump as a function of the wet-bulb temperature entering the coil and the outdoor dry-bulb temperature Qoperating Present load on heat pump (Btu/h) Qavailable Heat pump available capacity at present evaporator and condenser conditions (Btu/h). tdb The entering coil dry-bulb temperature (°F) twt The water supply temperature (°F) todb The outside air dry-bulb temperature (°F) Prated Rated power draw at ARI conditions (kW) Poperating Power draw at specified operating conditions (kW)

 Coefficient Air-and Water-Source EIR-FPLR Water-Source EIR-FT Air-Source EIR-FT a 0.0856522 1.3876102 2.4600298 b 0.9388137 0.0060479 -0.0622539 c -0.1834361 N/A 0.0008800 d 0.1589702 -0.0115852 -0.0000046
Units None
Input Restrictions User may input curves or use default curves. If defaults are overridden, documentation shall be provided.
Baseline Rules Use default curves
Applicability Electric Heat Pump Supplemental Heating Capacity All heat pumps The design heating capacity of a heat pump supplemental heating coil at ARI conditions Btu/h As designed Autosize
Applicability Electric Supplemental Heating Control Temp All heat pumps The outside dry-bulb temperature below which the heat pump supplemental heating is allowed to operate Degrees Fahrenheit (°F) As designed. Default to 40°F 40°F
Applicability Coil Defrost Air-cooled electric heat pump The defrost control mechanism for an air-cooled heat pump. The choices are: Hot-gas defrost, on-demand Hot-gas defrost, timed 3.5 minute cycle Electric resistance defrost, on-demand Electric resistance defrost, timed 3.5 minute cycle Defrost shall be enabled whenever the outside air dry-bulb temperature drops below 40°F. List (see above) Default to use hot-gas defrost, timed 3.5 minute cycle. User may select any of the above. The baseline building uses the default.
Applicability Coil Defrost kW Heat pumps with electric resistance defrost The capacity of the electric resistance defrost heater Kilowatts (kW) As designed. This descriptor defaults to 0 if nothing is entered. Not applicable. Baseline building systems 2 and 4 use hot-gas, timed 3.5 minute cycle.
Applicability Crank Case Heater kW All heat pumps The capacity of the electric resistance heater in the crank case of a direct expansion (DX) compressor. The crank case heater operates only when the compressor is off. Kilowatts (kW) As designed. This descriptor defaults to 0 if nothing is entered. Zero (0)
Applicability Crank Case Heater Shutoff Temperature All heat pumps The outdoor air dry-bulb temperature above which the crank case heater is not permitted to operate. Degrees Fahrenheit (°F) As designed. This descriptor defaults to 50°F. 50°F

## Heat Recovery

Exhaust to Outside Heat Recovery Effectiveness
Applicability Any system with outside air heat recovery
Definition

The effectiveness of an air-to-air heat exchanger between the building exhaust and entering outside air streams. Effectiveness is defined as follows:

(6.7.6-14)

$$H\!R\!E\!F\!F = \frac{\left ( E\!E\!A_{db} - E\!L\!A_{db}\right )}{\left ( E\!E\!A_{db} - O\!S\!A_{db}\right )}$$where

 HREFF The air-to-air heat exchanger effectiveness EEAdb The exhaust air dry-bulb temperature entering the heat exchanger ELAdb The exhaust air dry-bulb temperature leaving the heat exchanger OSAdb The outside air dry-bulb temperature
Units Ratio
Input Restrictions As designed
Baseline Rules Required for fan systems with a design supply air flow rate of 5,000 cfm or greater if the minimum outside air quantity is 70% of the design air flow rate. If required, the energy recovery system should have at least 50% effectiveness. Energy recovery is not required for heating systems in climate zones 1 through 3 or for cooling systems in climate zones 3c, 4c, 5b, 5c, 6b, 7 and 8.
Applicability Condenser Heat Recovery Effectiveness Systems that use recover heat from a condenser The percentage of heat rejection at design conditions from a DX or heat pump unit in cooling mode that is available for space or water heating. Percent (%) As designed. The software must indicate that supporting documentation is required on the output forms if heat recovery is specified. Not applicable for most conditions. Condenser heat recovery is required for 24-hour facilities when the heat rejection exceeds 6,000,000 Btu/h and the design service water heating load exceeds 1,000,000 Btu/h. When required, the effectiveness will be 60%.
Applicability Heat Recovery Use Systems that use heat recovery The end use of the heat recovered from a DX or heat pump unit. The choices are: Reheat coils Water heating List (see above) As designed. The software must indicate that supporting documentation is required on the output forms if heat recovery is specified. Not applicable for most conditions. The end use will be water heating if required for 24-hour facility operation.
90.1-2007

## /3765-electric-heat-pumpGeneral

Applicability Heating Source All systems that provide heating The source of heating for the heating and preheat coils. The choices are: Hot water Steam Electric resistance Electric heat pump Gas furnace Gas heat pump (optional feature) Oil furnace Heat recovery (for preheat coils in proposed designs) List (see above) As designed Based on the prescribed system type. Refer to the HVAC System Map in [bookref id="hvac-mapping"].

[table title="Heating Source for Baseline Building" id="heating-source-for-baseline-building"]

 Baseline Building System Heating Source System 1 – PTAC Gas Furnace System 2 – PTHP Heat pump System 3 – PSZ-AC Gas or Oil Furnace System 4 – PSZ-HP Heat pump System 5 – Packaged VAV with Reheat Hot water System 6 – Packaged VAV with PFP boxes Electric Resistance System 7 – VAV with Reheat Hot water System 8 – VAV with PFP boxes Electric Resistance

## Preheat Coil

Applicability Preheat Coil Capacity Systems with a preheat coil located in the outside air stream The heating capacity of a preheating coil at design conditions. Btu/h As designed If the proposed design has a preheat coil and it can be modeled in the baseline building system, then the baseline building also has a preheat coil sized to meet the preheat coil temperature specified for the proposed design. Autosize to maintain the preheat coil temperature of the proposed design.

## Heating Coils

Systems with boilers have heating coils, including baseline building systems 1, 5 and 7.

Applicability Heating Coil Capacity All systems with a heating coil The heating capacity of a heating coil at ARI conditions Btu/h As designed. Adjust the capacity if the number of unmet load hours exceeds 300. Autosize with a heating oversizing factor of 25%. If the number of unmet load hours for the proposed design exceeds the number of unmet load hours for the baseline building by more than 50, reduce the heating coil capacity as indicated in [bookref id="procedure-for-adjusting-equipment-hvac-sizes-in-the-baseline-building"].

## Furnace

Applicability Furnace Capacity Systems with a furnace The full load heating capacity of the unit Btu/h As designed. Adjust the capacity if the number of unmet load hours exceeds 300. Autosize with an oversizing factor of 25% (let the software determine heating capacity based on the building loads). If the number of unmet load hours for the proposed design exceeds the number of unmet load hours for the baseline building by more than 50, reduce the furnace capacity as indicated 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"].
Furnace Fuel Heating Efficiency
Applicability Systems with a furnace
Definition The full load thermal efficiency of either a gas or oil furnace at design conditions. The software must accommodate input in either Thermal Efficiency (Et) or Annual Fuel Utilization Efficiency (AFUE). Where AFUE is provided, Et shall be calculated as follows:

(6.7.6-1)

$1) All\ Single\ Package\ Equipment$
$E_t = 0.005163 \times AFUE + 0.4033$
$2) Split\ Systems, AFUE \leq 83.5$
$E_t = 0.002907 \times AFUE + 0.5787$
$3) Split\ Systems, AFUE \textgreater 83.5$
$E_t = 0.011116 \times AFUE - 0.098185$

where

 AFUE The annual fuel utilization efficiency (%) Et The thermal efficiency (fraction)
Units Fraction
Input Restrictions As designed
Baseline Rules Look up the requirement from the equipment efficiency tables in Table 6.8.1E of Standard 90.1-2007. Use the heating input of the proposed design system to determine the size category.
Furnace Fuel Heating Part Load Efficiency Curve
Applicability Systems with furnaces
Definition An adjustment factor that represents the percentage of full load fuel consumption as a function of the percentage full load capacity. This curve shall take the form of a quadratic equation as follows:

(6.7.6-2)

$$Fuel_{partload} = Fuel_{rated} \times F\!HeatP\!LC$$

(6.7.6-3)

$$F\!HeatP\!LC = \left ( a + b \times \frac{Q_{partload}}{Q_{rated}} + c \times \left( \frac{Q_{partload}}{Q_{rated}} \right )^2 \right )$$

where

 FHeatPLC The Fuel Heating Part Load Efficiency Curve Fuelpartload The fuel consumption at part load conditions (Btu/h) Fuelrated The fuel consumption at full load (Btu/h) Qpartload The capacity at part load conditions (Btu/h) Qrated The capacity at rated conditions (Btu/h)

[table title="Furnace Efficiency Curve Coefficients" id="furnace-efficiency-curve-coefficients"]

 Coefficient Furnace a 0.0186100 b 1.0942090 c -0.1128190
Units Data structure
Input Restrictions As designed when data is available, otherwise use the default values are provided above.
Baseline Rules Use defaults
Applicability Furnace Fuel Heating Pilot Systems that use a furnace for heating The fuel input for a pilot light on a furnace Btu/h As designed Zero (pilotless ignition)
Applicability Furnace Fuel Heating Fan/Auxiliary Systems that use a furnace for heating The fan energy in forced draft furnaces and the auxiliary (pumps and outdoor fan) energy in fuel-fired heat pumps Kilowatts (kW) As designed Not applicable

## Electric Heat Pump

Applicability Electric Heat Pump Heating Capacity All heat pumps The full load heating capacity of the unit, excluding supplemental heating capacity at ARI rated conditions Btu/h As designed Autosize and use an oversizing factor of 25% (let the software determine heating capacity based on the building loads). The autosized equipment may need to be downsized to achieve a maximum difference in unmet load hours between the proposed design and the baseline building of 50.
Applicability Electric Heat Pump Supplemental Heating Source All heat pumps The auxiliary heating source for a heat pump heating system. The common control sequence is to lock out the heat pump compressor when the supplemental heat is activated. Other building descriptors may be needed if this is not the case. Choices for supplemental heat include: Electric resistance Gas furnace Oil furnace Hot water Other List (see above) As designed Electric resistance
Electric Heat Pump Heating Efficiency
Applicability All heat pumps
Definition

The heating efficiency of a heat pump at ARI rated conditions as a dimensionless ratio of output over input. The software must accommodate user input in terms of either the Coefficient of Performance (COP) or the Heating Season Performance Factor (HSPF). Where HSPF is provided, COP shall be calculated as follows:

(6.7.6-4)

$1) All\ Single\ Package\ Equipment$
$C\!O\!P = 0.2778 \times H\!S\!P\!F + 0.9667$
$2) All\ Split\ Systems$
$C\!O\!P = 0.4813 \times H\!S\!P\!F - 0.2606$

For all unitary and applied equipment where the fan energy is part of the equipment efficiency rating, the COP shall be adjusted as follows to remove the fan energy:

(6.7.6-5)

$$C\!O\!P_{adj} = \frac{\frac{H\!C\!A\!P_{rated}}{3.413} - B\!H\!P_{supply} \times 0.7457}{\frac{H\!C\!A\!P_{rated}}{C\!O\!P \times 3.413} - B\!H\!P_{supply} \times 0.7457}$$

where

 COPadj The adjusted coefficient of performance for simulation purposes COP The ARI rated coefficient of performance HCAPrated The ARI rated heating capacity of a packaged unit (kBtu/h) BHPsupply The supply fan brake horsepower (bhp).

Refer to building descriptor Supply Fan BHP.

Units Unitless
Input Restrictions As designed
Baseline Rules For the purpose of green building ratings, look up the requirement from the equipment efficiency Table 6.8.1B and Table 6.8.1D in ASHRAE Standard 90.1-2007. Use the heating capacity of the proposed design to determine the size category.
Electric Heat Pump Heating Capacity Adjustment Curve(s)
Applicability All heat pumps
Definition

A curve or group of curves that represent the available heat-pump heating capacity as a function of evaporator and condenser conditions. The default curves are given as follows:

(6.7.6-6)

$$Q_{available} = C\!A\!P\_FT \times Q_{rated}$$For air-cooled heat pumps:

(6.7.6-7)

$$C\!A\!P\_FT = a + b \times t_{odb} + c \times \left. t_{odb}\right. ^2 + d \times \left. t_{odb}\right. ^3$$

For water-cooled heat pumps:

(6.7.6-8)

$$C\!A\!P\_FT = a + b \times t_{db} + d \times t_{wt}$$

where

 Qavailable Available heating capacity at present evaporator and condenser conditions (kBtu/h) tdb The entering coil dry-bulb temperature (°F) twt The water supply temperature (°F) todb The outside-air dry-bulb temperature (°F) Qrated Rated capacity at ARI conditions (in kBtu/h

 Coefficient Water-Source Air-Source a 0.4886534 0.2536714 b -0.0067774 0.0104351 c N/A 0.0001861 d 0.0140823 -0.0000015
Units Data structure
Input Restrictions User may input curves or use default curves. If defaults are overridden, supporting documentation shall be provided.
Baseline Rules Use default curves.
Electric Heat Pump Heating Efficiency Adjustment Curve(s)
Applicability All heat pumps
Definition

A curve or group of curves that varies the heat-pump heating efficiency as a function of evaporator conditions, condenser conditions and part-load ratio. The default curves are given as follows:

(6.7.6-9)

$$P\!LR = \frac{Q_{operating}}{Q_{available}\left ( t_{db},t_{odb/wt}\right )}$$

(6.7.6-10)

$$E\!I\!R\_F\!P\!LR = a + b \times P\!LR + c \times P\!LR^2 + d \times P\!LR^3$$

Air Source Heat Pumps:

(6.7.6-11)

$$E\!I\!R\_FT = a + b \times \left ( \frac{t_{odb}}{t_{db}} \right ) + c \times \left ( \frac{t_{odb}}{t_{db}} \right ) ^2 + d \times \left ( \frac{t_{odb}}{t_{db}} \right )^3$$Water Source Heat Pumps:

(6.7.6-12)

$$E\!I\!R\_FT = a + b \times t_{wt} + d \times t_{db}$$

(6.7.6-13)

$$P_{operating} = P_{rated} \times E\!I\!R\_F\!P\!LR \times E\!I\!R\_FT \times C\!AP\_FT$$

where

 PLR Part load ratio based on available capacity (not rated capacity) EIR-FPLR A multiplier on the EIR of the heat pump as a function of part load ratio EIR-FT A multiplier on the EIR of the heat pump as a function of the wet-bulb temperature entering the coil and the outdoor dry-bulb temperature Qoperating Present load on heat pump (Btu/h) Qavailable Heat pump available capacity at present evaporator and condenser conditions (Btu/h). tdb The entering coil dry-bulb temperature (°F) twt The water supply temperature (°F) todb The outside air dry-bulb temperature (°F) Prated Rated power draw at ARI conditions (kW) Poperating Power draw at specified operating conditions (kW)

 Coefficient Air-and Water-Source EIR-FPLR Water-Source EIR-FT Air-Source EIR-FT a 0.0856522 1.3876102 2.4600298 b 0.9388137 0.0060479 -0.0622539 c -0.1834361 N/A 0.0008800 d 0.1589702 -0.0115852 -0.0000046
Units None
Input Restrictions User may input curves or use default curves. If defaults are overridden, documentation shall be provided.
Baseline Rules Use default curves
Applicability Electric Heat Pump Supplemental Heating Capacity All heat pumps The design heating capacity of a heat pump supplemental heating coil at ARI conditions Btu/h As designed Autosize
Applicability Electric Supplemental Heating Control Temp All heat pumps The outside dry-bulb temperature below which the heat pump supplemental heating is allowed to operate Degrees Fahrenheit (°F) As designed. Default to 40°F 40°F
Applicability Coil Defrost Air-cooled electric heat pump The defrost control mechanism for an air-cooled heat pump. The choices are: Hot-gas defrost, on-demand Hot-gas defrost, timed 3.5 minute cycle Electric resistance defrost, on-demand Electric resistance defrost, timed 3.5 minute cycle Defrost shall be enabled whenever the outside air dry-bulb temperature drops below 40°F. List (see above) Default to use hot-gas defrost, timed 3.5 minute cycle. User may select any of the above. The baseline building uses the default.
Applicability Coil Defrost kW Heat pumps with electric resistance defrost The capacity of the electric resistance defrost heater Kilowatts (kW) As designed. This descriptor defaults to 0 if nothing is entered. Not applicable. Baseline building systems 2 and 4 use hot-gas, timed 3.5 minute cycle.
Applicability Crank Case Heater kW All heat pumps The capacity of the electric resistance heater in the crank case of a direct expansion (DX) compressor. The crank case heater operates only when the compressor is off. Kilowatts (kW) As designed. This descriptor defaults to 0 if nothing is entered. Zero (0)
Applicability Crank Case Heater Shutoff Temperature All heat pumps The outdoor air dry-bulb temperature above which the crank case heater is not permitted to operate. Degrees Fahrenheit (°F) As designed. This descriptor defaults to 50°F. 50°F

## Heat Recovery

Exhaust to Outside Heat Recovery Effectiveness
Applicability Any system with outside air heat recovery
Definition

The effectiveness of an air-to-air heat exchanger between the building exhaust and entering outside air streams. Effectiveness is defined as follows:

(6.7.6-14)

$$H\!R\!E\!F\!F = \frac{\left ( E\!E\!A_{db} - E\!L\!A_{db}\right )}{\left ( E\!E\!A_{db} - O\!S\!A_{db}\right )}$$where

 HREFF The air-to-air heat exchanger effectiveness EEAdb The exhaust air dry-bulb temperature entering the heat exchanger ELAdb The exhaust air dry-bulb temperature leaving the heat exchanger OSAdb The outside air dry-bulb temperature
Units Ratio
Input Restrictions As designed
Baseline Rules Required for fan systems with a design supply air flow rate of 5,000 cfm or greater if the minimum outside air quantity is 70% of the design air flow rate. If required, the energy recovery system should have at least 50% effectiveness. Energy recovery is not required for heating systems in climate zones 1 through 3 or for cooling systems in climate zones 3c, 4c, 5b, 5c, 6b, 7 and 8.
Applicability Condenser Heat Recovery Effectiveness Systems that use recover heat from a condenser The percentage of heat rejection at design conditions from a DX or heat pump unit in cooling mode that is available for space or water heating. Percent (%) As designed. The software must indicate that supporting documentation is required on the output forms if heat recovery is specified. Not applicable for most conditions. Condenser heat recovery is required for 24-hour facilities when the heat rejection exceeds 6,000,000 Btu/h and the design service water heating load exceeds 1,000,000 Btu/h. When required, the effectiveness will be 60%.
Applicability Heat Recovery Use Systems that use heat recovery The end use of the heat recovered from a DX or heat pump unit. The choices are: Reheat coils Water heating List (see above) As designed. The software must indicate that supporting documentation is required on the output forms if heat recovery is specified. Not applicable for most conditions. The end use will be water heating if required for 24-hour facility operation.
90.1-2010

## General

Applicability Heating Source All systems that provide heating The source of heating for the heating and preheat coils. The choices are: Hot water Steam Electric resistance Electric heat pump Gas furnace Gas heat pump (optional feature) Oil furnace Heat recovery (for preheat coils in proposed designs) List (see above) As designed Based on the prescribed system type. Refer to the HVAC System Map in Figure 6.1.2-1.

Table 6.7.6-1: Heating Source for Baseline Building

 Baseline Building System Heating Source System 1 – PTAC Gas Furnace System 2 – PTHP Heat pump System 3 – PSZ-AC Gas or Oil Furnace System 4 – PSZ-HP Heat pump System 5 – Packaged VAV with Reheat Hot water System 6 – Packaged VAV with PFP boxes Electric Resistance System 7 – VAV with Reheat Hot water System 8 – VAV with PFP boxes Electric Resistance System 9 – Heating and Ventilation Electric Resistance System 10 – Heating and Ventilation Gas Furnace

## Preheat Coil

Applicability Preheat Coil Capacity Systems with a preheat coil located in the outside air stream The heating capacity of a preheating coil at design conditions. Btu/h As designed If the proposed design has a preheat coil and it can be modeled in the baseline building system, then the baseline building also has a preheat coil sized to meet the preheat coil temperature specified for the proposed design. Autosize to maintain the preheat coil temperature of the proposed design.

## Heating Coils

Systems with boilers have heating coils, including baseline building systems 1, 5 and 7.

Applicability Heating Coil Capacity All systems with a heating coil The heating capacity of a heating coil at ARI conditions Btu/h As designed. Adjust the capacity if the number of unmet load hours exceeds 300. Autosize with a heating oversizing factor of 25%.

## Furnace

Applicability Furnace Capacity Systems with a furnace The full load heating capacity of the unit Btu/h As designed. Adjust the capacity if the number of unmet load hours exceeds 300. Autosize with an oversizing factor of 25% (let the software determine heating capacity based on the building loads).
Furnace Fuel Heating Efficiency
Applicability Systems with a furnace
Definition The full load thermal efficiency of either a gas or oil furnace at design conditions. The software must accommodate input in either Thermal Efficiency (Et) or Annual Fuel Utilization Efficiency (AFUE). Where AFUE is provided, Et shall be calculated as follows:

(6.7.6-1)

$1) All\ Single\ Package\ Equipment$
$E_t = 0.005163 \times AFUE + 0.4033$
$2) Split\ Systems, AFUE \leq 83.5$
$E_t = 0.002907 \times AFUE + 0.5787$
$3) Split\ Systems, AFUE \textgreater 83.5$
$E_t = 0.011116 \times AFUE - 0.098185$

where

 AFUE The annual fuel utilization efficiency (%) Et The thermal efficiency (fraction)
Units Fraction
Input Restrictions As designed
Baseline Rules Look up the requirement from the equipment efficiency tables in Table 6.8.1E of Standard 90.1-2007. Use the heating input of the proposed design system to determine the size category.
Furnace Fuel Heating Part Load Efficiency Curve
Applicability Systems with furnaces
Definition An adjustment factor that represents the percentage of full load fuel consumption as a function of the percentage full load capacity. This curve shall take the form of a quadratic equation as follows:

(6.7.6-2)

$$Fuel_{partload} = Fuel_{rated} \times F\!HeatP\!LC$$

(6.7.6-3)

$$F\!HeatP\!LC = \left ( a + b \times \frac{Q_{partload}}{Q_{rated}} + c \times \left( \frac{Q_{partload}}{Q_{rated}} \right )^2 \right )$$

where

 FHeatPLC The Fuel Heating Part Load Efficiency Curve Fuelpartload The fuel consumption at part load conditions (Btu/h) Fuelrated The fuel consumption at full load (Btu/h) Qpartload The capacity at part load conditions (Btu/h) Qrated The capacity at rated conditions (Btu/h)

Table 6.7.6-2: Furnace Efficiency Curve Coefficients

 Coefficient Furnace a 0.0186100 b 1.0942090 c -0.1128190
Units Data structure
Input Restrictions As designed when data is available, otherwise use the default values are provided above.
Baseline Rules Use defaults
Applicability Furnace Fuel Heating Pilot Systems that use a furnace for heating The fuel input for a pilot light on a furnace Btu/h As designed Zero (pilotless ignition)
Applicability Furnace Fuel Heating Fan/Auxiliary Systems that use a furnace for heating The fan energy in forced draft furnaces and the auxiliary (pumps and outdoor fan) energy in fuel-fired heat pumps Kilowatts (kW) As designed Not applicable

## Electric Heat Pump

Applicability Electric Heat Pump Heating Capacity All heat pumps The full load heating capacity of the unit, excluding supplemental heating capacity at ARI rated conditions Btu/h As designed Autosize and use an oversizing factor of 25% (let the software determine heating capacity based on the building loads). The autosized equipment may need to be downsized to achieve a maximum difference in unmet load hours between the proposed design and the baseline building of 50.
Applicability Electric Heat Pump Supplemental Heating Source All heat pumps The auxiliary heating source for a heat pump heating system. The common control sequence is to lock out the heat pump compressor when the supplemental heat is activated. Other building descriptors may be needed if this is not the case. Choices for supplemental heat include: Electric resistance Gas furnace Oil furnace Hot water Other List (see above) As designed Electric resistance
Electric Heat Pump Heating Efficiency
Applicability All heat pumps
Definition

The heating efficiency of a heat pump at ARI rated conditions as a dimensionless ratio of output over input. The software must accommodate user input in terms of either the Coefficient of Performance (COP) or the Heating Season Performance Factor (HSPF). Where HSPF is provided, COP shall be calculated as follows:

(6.7.6-4)

$1) All\ Single\ Package\ Equipment$
$C\!O\!P = 0.2778 \times H\!S\!P\!F + 0.9667$
$2) All\ Split\ Systems$
$C\!O\!P = 0.4813 \times H\!S\!P\!F - 0.2606$

For all unitary and applied equipment where the fan energy is part of the equipment efficiency rating, the COP shall be adjusted as follows to remove the fan energy:

(6.7.6-5)

$$C\!O\!P_{adj} = \frac{\frac{H\!C\!A\!P_{rated}}{3.413} - B\!H\!P_{supply} \times 0.7457}{\frac{H\!C\!A\!P_{rated}}{C\!O\!P \times 3.413} - B\!H\!P_{supply} \times 0.7457}$$

where

 COPadj The adjusted coefficient of performance for simulation purposes COP The ARI rated coefficient of performance HCAPrated The ARI rated heating capacity of a packaged unit (kBtu/h) BHPsupply The supply fan brake horsepower (bhp).

Refer to building descriptor Supply Fan BHP.

Units Unitless
Input Restrictions As designed
Baseline Rules For the purpose of green building ratings, look up the requirement from the equipment efficiency Table 6.8.1B and Table 6.8.1D in ASHRAE Standard 90.1-2007. Use the heating capacity of the proposed design to determine the size category.
Electric Heat Pump Heating Capacity Adjustment Curve(s)
Applicability All heat pumps
Definition

A curve or group of curves that represent the available heat-pump heating capacity as a function of evaporator and condenser conditions. The default curves are given as follows:

(6.7.6-6)

$$Q_{available} = C\!A\!P\_FT \times Q_{rated}$$For air-cooled heat pumps:

(6.7.6-7)

$$C\!A\!P\_FT = a + b \times t_{odb} + c \times \left. t_{odb}\right. ^2 + d \times \left. t_{odb}\right. ^3$$

For water-cooled heat pumps:

(6.7.6-8)

$$C\!A\!P\_FT = a + b \times t_{db} + d \times t_{wt}$$

where

 Qavailable Available heating capacity at present evaporator and condenser conditions (kBtu/h) tdb The entering coil dry-bulb temperature (°F) twt The water supply temperature (°F) todb The outside-air dry-bulb temperature (°F) Qrated Rated capacity at ARI conditions (in kBtu/h

Table 6.7.6-3: Heat Pump Capacity Adjustment Curves (CAP-FT)

 Coefficient Water-Source Air-Source a 0.4886534 0.2536714 b -0.0067774 0.0104351 c N/A 0.0001861 d 0.0140823 -0.0000015
Units Data structure
Input Restrictions User may input curves or use default curves. If defaults are overridden, supporting documentation shall be provided.
Baseline Rules Use default curves.
Electric Heat Pump Heating Efficiency Adjustment Curve(s)
Applicability All heat pumps
Definition

A curve or group of curves that varies the heat-pump heating efficiency as a function of evaporator conditions, condenser conditions and part-load ratio. The default curves are given as follows:

(6.7.6-9)

$$P\!LR = \frac{Q_{operating}}{Q_{available}\left ( t_{db},t_{odb/wt}\right )}$$

(6.7.6-10)

$$E\!I\!R\_F\!P\!LR = a + b \times P\!LR + c \times P\!LR^2 + d \times P\!LR^3$$

Air Source Heat Pumps:

(6.7.6-11)

$$E\!I\!R\_FT = a + b \times \left ( \frac{t_{odb}}{t_{db}} \right ) + c \times \left ( \frac{t_{odb}}{t_{db}} \right ) ^2 + d \times \left ( \frac{t_{odb}}{t_{db}} \right )^3$$Water Source Heat Pumps:

(6.7.6-12)

$$E\!I\!R\_FT = a + b \times t_{wt} + d \times t_{db}$$

(6.7.6-13)

$$P_{operating} = P_{rated} \times E\!I\!R\_F\!P\!LR \times E\!I\!R\_FT \times C\!AP\_FT$$

where

 PLR Part load ratio based on available capacity (not rated capacity) EIR-FPLR A multiplier on the EIR of the heat pump as a function of part load ratio EIR-FT A multiplier on the EIR of the heat pump as a function of the wet-bulb temperature entering the coil and the outdoor dry-bulb temperature Qoperating Present load on heat pump (Btu/h) Qavailable Heat pump available capacity at present evaporator and condenser conditions (Btu/h). tdb The entering coil dry-bulb temperature (°F) twt The water supply temperature (°F) todb The outside air dry-bulb temperature (°F) Prated Rated power draw at ARI conditions (kW) Poperating Power draw at specified operating conditions (kW)

Table 6.7.6-4: Heat Pump Heating Efficiency Adjustment (Curves)

 Coefficient Air-and Water-Source EIR-FPLR Water-Source EIR-FT Air-Source EIR-FT a 0.0856522 1.3876102 2.4600298 b 0.9388137 0.0060479 -0.0622539 c -0.1834361 N/A 0.0008800 d 0.1589702 -0.0115852 -0.0000046
Units None
Input Restrictions User may input curves or use default curves. If defaults are overridden, documentation shall be provided.
Baseline Rules Use default curves
Applicability Electric Heat Pump Supplemental Heating Capacity All heat pumps The design heating capacity of a heat pump supplemental heating coil at ARI conditions Btu/h As designed Autosize
Applicability Electric Supplemental Heating Control Temp All heat pumps The outside dry-bulb temperature below which the heat pump supplemental heating is allowed to operate Degrees Fahrenheit (°F) As designed. Default to 40°F 40°F
Applicability Coil Defrost Air-cooled electric heat pump The defrost control mechanism for an air-cooled heat pump. The choices are: Hot-gas defrost, on-demand Hot-gas defrost, timed 3.5 minute cycle Electric resistance defrost, on-demand Electric resistance defrost, timed 3.5 minute cycle Defrost shall be enabled whenever the outside air dry-bulb temperature drops below 40°F. List (see above) Default to use hot-gas defrost, timed 3.5 minute cycle. User may select any of the above. The baseline building uses the default.
Applicability Coil Defrost kW Heat pumps with electric resistance defrost The capacity of the electric resistance defrost heater Kilowatts (kW) As designed. This descriptor defaults to 0 if nothing is entered. Not applicable. Baseline building systems 2 and 4 use hot-gas, timed 3.5 minute cycle.
Applicability Crank Case Heater kW All heat pumps The capacity of the electric resistance heater in the crank case of a direct expansion (DX) compressor. The crank case heater operates only when the compressor is off. Kilowatts (kW) As designed. This descriptor defaults to 0 if nothing is entered. Zero (0)
Applicability Crank Case Heater Shutoff Temperature All heat pumps The outdoor air dry-bulb temperature above which the crank case heater is not permitted to operate. Degrees Fahrenheit (°F) As designed. This descriptor defaults to 50°F. 50°F

## Heat Recovery

Exhaust to Outside Heat Recovery Effectiveness
Applicability Any system with outside air heat recovery
Definition

The effectiveness of an air-to-air heat exchanger between the building exhaust and entering outside air streams. Effectiveness is defined as follows:

(6.7.6-14)

$$H\!R\!E\!F\!F = \frac{\left ( E\!E\!A_{db} - E\!L\!A_{db}\right )}{\left ( E\!E\!A_{db} - O\!S\!A_{db}\right )}$$where

 HREFF The air-to-air heat exchanger effectiveness EEAdb The exhaust air dry-bulb temperature entering the heat exchanger ELAdb The exhaust air dry-bulb temperature leaving the heat exchanger OSAdb The outside air dry-bulb temperature
Units Ratio
Input Restrictions As designed
Baseline Rules Required for fan systems with a design supply air flow rate of 5,000 cfm or greater if the minimum outside air quantity is 70% of the design air flow rate. If required, the energy recovery system should have at least 50% effectiveness. Energy recovery is not required for heating systems in climate zones 1 through 3 or for cooling systems in climate zones 3c, 4c, 5b, 5c, 6b, 7 and 8.
Applicability Condenser Heat Recovery Effectiveness Systems that use recover heat from a condenser The percentage of heat rejection at design conditions from a DX or heat pump unit in cooling mode that is available for space or water heating. Percent (%) As designed. The software must indicate that supporting documentation is required on the output forms if heat recovery is specified. Not applicable for most conditions. Condenser heat recovery is required for 24-hour facilities when the heat rejection exceeds 6,000,000 Btu/h and the design service water heating load exceeds 1,000,000 Btu/h. When required, the effectiveness will be 60%.
Applicability Heat Recovery Use Systems that use heat recovery The end use of the heat recovered from a DX or heat pump unit. The choices are: Reheat coils Water heating List (see above) As designed. The software must indicate that supporting documentation is required on the output forms if heat recovery is specified. Not applicable for most conditions. The end use will be water heating if required for 24-hour facility operation.
90.1-2016 BM
Building EQ

## General

Applicability Heating Source All systems that provide heating The source of heating for the heating and preheat coils. The choices are: Hot water Steam Electric resistance Electric heat pump Gas furnace Gas heat pump (optional feature) Oil furnace Heat recovery (for preheat coils in proposed designs) List (see above) As designed

## Preheat Coil

Applicability Preheat Coil Capacity Systems with a preheat coil located in the outside air stream The heating capacity of a preheating coil at design conditions. Btu/h As designed

## Heating Coils

Applicability Heating Coil Capacity All systems with a heating coil The heating capacity of a heating coil at ARI conditions Btu/h As designed. Adjust the capacity if the number of unmet load hours exceeds 300.

## Furnace

Applicability Furnace Capacity Systems with a furnace The full load heating capacity of the unit Btu/h As designed. Adjust the capacity if the number of unmet load hours exceeds 300.
Furnace Fuel Heating Efficiency
Applicability Systems with a furnace
Definition The full load thermal efficiency of either a gas or oil furnace at design conditions. The software must accommodate input in either Thermal Efficiency (Et) or Annual Fuel Utilization Efficiency (AFUE). Where AFUE is provided, Et shall be calculated as follows:

(6.7.6-1)

$1) All\ Single\ Package\ Equipment$
$E_t = 0.005163 \times AFUE + 0.4033$
$2) Split\ Systems, AFUE \leq 83.5$
$E_t = 0.002907 \times AFUE + 0.5787$
$3) Split\ Systems, AFUE \textgreater 83.5$
$E_t = 0.011116 \times AFUE - 0.098185$

where

 AFUE The annual fuel utilization efficiency (%) Et The thermal efficiency (fraction)
Units Fraction
Input Restrictions As designed
Furnace Fuel Heating Part Load Efficiency Curve
Applicability Systems with furnaces
Definition An adjustment factor that represents the percentage of full load fuel consumption as a function of the percentage full load capacity. This curve shall take the form of a quadratic equation as follows:

(6.7.6-2)

$$Fuel_{partload} = Fuel_{rated} \times F\!HeatP\!LC$$

(6.7.6-3)

$$F\!HeatP\!LC = \left ( a + b \times \frac{Q_{partload}}{Q_{rated}} + c \times \left( \frac{Q_{partload}}{Q_{rated}} \right )^2 \right )$$

where

 FHeatPLC The Fuel Heating Part Load Efficiency Curve Fuelpartload The fuel consumption at part load conditions (Btu/h) Fuelrated The fuel consumption at full load (Btu/h) Qpartload The capacity at part load conditions (Btu/h) Qrated The capacity at rated conditions (Btu/h)

[table title="Furnace Efficiency Curve Coefficients" id="furnace-efficiency-curve-coefficients"]

 Coefficient Furnace a 0.0186100 b 1.0942090 c -0.1128190
Units Data structure
Input Restrictions As designed when data is available, otherwise use the default values are provided above.
Applicability Furnace Fuel Heating Pilot Systems that use a furnace for heating The fuel input for a pilot light on a furnace Btu/h As designed
Applicability Furnace Fuel Heating Fan/Auxiliary Systems that use a furnace for heating The fan energy in forced draft furnaces and the auxiliary (pumps and outdoor fan) energy in fuel-fired heat pumps Kilowatts (kW) As designed

## Electric Heat Pump

Applicability Electric Heat Pump Heating Capacity All heat pumps The full load heating capacity of the unit, excluding supplemental heating capacity at ARI rated conditions Btu/h As designed
Applicability Electric Heat Pump Supplemental Heating Source All heat pumps The auxiliary heating source for a heat pump heating system. The common control sequence is to lock out the heat pump compressor when the supplemental heat is activated. Other building descriptors may be needed if this is not the case. Choices for supplemental heat include: Electric resistance Gas furnace Oil furnace Hot water Other List (see above) As designed
Electric Heat Pump Heating Efficiency
Applicability All heat pumps
Definition

The heating efficiency of a heat pump at ARI rated conditions as a dimensionless ratio of output over input. The software must accommodate user input in terms of either the Coefficient of Performance (COP) or the Heating Season Performance Factor (HSPF). Where HSPF is provided, COP shall be calculated as follows:

(6.7.6-4)

$1) All\ Single\ Package\ Equipment$
$C\!O\!P = 0.2778 \times H\!S\!P\!F + 0.9667$
$2) All\ Split\ Systems$
$C\!O\!P = 0.4813 \times H\!S\!P\!F - 0.2606$

For all unitary and applied equipment where the fan energy is part of the equipment efficiency rating, the COP shall be adjusted as follows to remove the fan energy:

(6.7.6-5)

$$C\!O\!P_{adj} = \frac{\frac{H\!C\!A\!P_{rated}}{3.413} - B\!H\!P_{supply} \times 0.7457}{\frac{H\!C\!A\!P_{rated}}{C\!O\!P \times 3.413} - B\!H\!P_{supply} \times 0.7457}$$

where

 COPadj The adjusted coefficient of performance for simulation purposes COP The ARI rated coefficient of performance HCAPrated The ARI rated heating capacity of a packaged unit (kBtu/h) BHPsupply The supply fan brake horsepower (bhp).

Refer to building descriptor Supply Fan BHP.

Units Unitless
Input Restrictions As designed
Electric Heat Pump Heating Capacity Adjustment Curve(s)
Applicability All heat pumps
Definition

A curve or group of curves that represent the available heat-pump heating capacity as a function of evaporator and condenser conditions. The default curves are given as follows:

(6.7.6-6)

$$Q_{available} = C\!A\!P\_FT \times Q_{rated}$$For air-cooled heat pumps:

(6.7.6-7)

$$C\!A\!P\_FT = a + b \times t_{odb} + c \times \left. t_{odb}\right. ^2 + d \times \left. t_{odb}\right. ^3$$

For water-cooled heat pumps:

(6.7.6-8)

$$C\!A\!P\_FT = a + b \times t_{db} + d \times t_{wt}$$

where

 Qavailable Available heating capacity at present evaporator and condenser conditions (kBtu/h) tdb The entering coil dry-bulb temperature (°F) twt The water supply temperature (°F) todb The outside-air dry-bulb temperature (°F) Qrated Rated capacity at ARI conditions (in kBtu/h

 Coefficient Water-Source Air-Source a 0.4886534 0.2536714 b -0.0067774 0.0104351 c N/A 0.0001861 d 0.0140823 -0.0000015
Units Data structure
Input Restrictions User may input curves or use default curves. If defaults are overridden, supporting documentation shall be provided.
Electric Heat Pump Heating Efficiency Adjustment Curve(s)
Applicability All heat pumps
Definition

A curve or group of curves that varies the heat-pump heating efficiency as a function of evaporator conditions, condenser conditions and part-load ratio. The default curves are given as follows:

(6.7.6-9)

$$P\!LR = \frac{Q_{operating}}{Q_{available}\left ( t_{db},t_{odb/wt}\right )}$$

(6.7.6-10)

$$E\!I\!R\_F\!P\!LR = a + b \times P\!LR + c \times P\!LR^2 + d \times P\!LR^3$$

Air Source Heat Pumps:

(6.7.6-11)

$$E\!I\!R\_FT = a + b \times \left ( \frac{t_{odb}}{t_{db}} \right ) + c \times \left ( \frac{t_{odb}}{t_{db}} \right ) ^2 + d \times \left ( \frac{t_{odb}}{t_{db}} \right )^3$$Water Source Heat Pumps:

(6.7.6-12)

$$E\!I\!R\_FT = a + b \times t_{wt} + d \times t_{db}$$

(6.7.6-13)

$$P_{operating} = P_{rated} \times E\!I\!R\_F\!P\!LR \times E\!I\!R\_FT \times C\!AP\_FT$$

where

 PLR Part load ratio based on available capacity (not rated capacity) EIR-FPLR A multiplier on the EIR of the heat pump as a function of part load ratio EIR-FT A multiplier on the EIR of the heat pump as a function of the wet-bulb temperature entering the coil and the outdoor dry-bulb temperature Qoperating Present load on heat pump (Btu/h) Qavailable Heat pump available capacity at present evaporator and condenser conditions (Btu/h). tdb The entering coil dry-bulb temperature (°F) twt The water supply temperature (°F) todb The outside air dry-bulb temperature (°F) Prated Rated power draw at ARI conditions (kW) Poperating Power draw at specified operating conditions (kW)

 Coefficient Air-and Water-Source EIR-FPLR Water-Source EIR-FT Air-Source EIR-FT a 0.0856522 1.3876102 2.4600298 b 0.9388137 0.0060479 -0.0622539 c -0.1834361 N/A 0.0008800 d 0.1589702 -0.0115852 -0.0000046
Units None
Input Restrictions User may input curves or use default curves. If defaults are overridden, documentation shall be provided.
Applicability Electric Heat Pump Supplemental Heating Capacity All heat pumps The design heating capacity of a heat pump supplemental heating coil at ARI conditions Btu/h As designed
Applicability Electric Supplemental Heating Control Temp All heat pumps The outside dry-bulb temperature below which the heat pump supplemental heating is allowed to operate Degrees Fahrenheit (°F) As designed. Default to 40°F
Applicability Coil Defrost Air-cooled electric heat pump The defrost control mechanism for an air-cooled heat pump. The choices are: Hot-gas defrost, on-demand Hot-gas defrost, timed 3.5 minute cycle Electric resistance defrost, on-demand Electric resistance defrost, timed 3.5 minute cycle Defrost shall be enabled whenever the outside air dry-bulb temperature drops below 40°F. List (see above) Default to use hot-gas defrost, timed 3.5 minute cycle. User may select any of the above.
Applicability Coil Defrost kW Heat pumps with electric resistance defrost The capacity of the electric resistance defrost heater Kilowatts (kW) As designed. This descriptor defaults to 0 if nothing is entered.
Applicability Crank Case Heater kW All heat pumps The capacity of the electric resistance heater in the crank case of a direct expansion (DX) compressor. The crank case heater operates only when the compressor is off. Kilowatts (kW) As designed. This descriptor defaults to 0 if nothing is entered.
Applicability Crank Case Heater Shutoff Temperature All heat pumps The outdoor air dry-bulb temperature above which the crank case heater is not permitted to operate. Degrees Fahrenheit (°F) As designed. This descriptor defaults to 50°F.

## Heat Recovery

Exhaust to Outside Heat Recovery Effectiveness
Applicability Any system with outside air heat recovery
Definition

The effectiveness of an air-to-air heat exchanger between the building exhaust and entering outside air streams. Effectiveness is defined as follows:

(6.7.6-14)

$$H\!R\!E\!F\!F = \frac{\left ( E\!E\!A_{db} - E\!L\!A_{db}\right )}{\left ( E\!E\!A_{db} - O\!S\!A_{db}\right )}$$where

 HREFF The air-to-air heat exchanger effectiveness EEAdb The exhaust air dry-bulb temperature entering the heat exchanger ELAdb The exhaust air dry-bulb temperature leaving the heat exchanger OSAdb The outside air dry-bulb temperature
Units Ratio
Input Restrictions As designed
Applicability Condenser Heat Recovery Effectiveness Systems that use recover heat from a condenser The percentage of heat rejection at design conditions from a DX or heat pump unit in cooling mode that is available for space or water heating. Percent (%) As designed. The software must indicate that supporting documentation is required on the output forms if heat recovery is specified.
Applicability Heat Recovery Use Systems that use heat recovery The end use of the heat recovered from a DX or heat pump unit. The choices are: Reheat coils Water heating List (see above) As designed. The software must indicate that supporting documentation is required on the output forms if heat recovery is specified.
Energy Star

## General

Applicability Heating Source All systems that provide heating The source of heating for the heating and preheat coils. The choices are: Hot water Steam Electric resistance Electric heat pump Gas furnace Gas heat pump (optional feature) Oil furnace Heat recovery (for preheat coils in proposed designs) List (see above) As designed

## Preheat Coil

Applicability Preheat Coil Capacity Systems with a preheat coil located in the outside air stream The heating capacity of a preheating coil at design conditions. Btu/h As designed

## Heating Coils

Applicability Heating Coil Capacity All systems with a heating coil The heating capacity of a heating coil at ARI conditions Btu/h As designed. Adjust the capacity if the number of unmet load hours exceeds 300.

## Furnace

Applicability Furnace Capacity Systems with a furnace The full load heating capacity of the unit Btu/h As designed. Adjust the capacity if the number of unmet load hours exceeds 300.
Furnace Fuel Heating Efficiency
Applicability Systems with a furnace
Definition The full load thermal efficiency of either a gas or oil furnace at design conditions. The software must accommodate input in either Thermal Efficiency (Et) or Annual Fuel Utilization Efficiency (AFUE). Where AFUE is provided, Et shall be calculated as follows:

(6.7.6-1)

$1) All\ Single\ Package\ Equipment$
$E_t = 0.005163 \times AFUE + 0.4033$
$2) Split\ Systems, AFUE \leq 83.5$
$E_t = 0.002907 \times AFUE + 0.5787$
$3) Split\ Systems, AFUE \textgreater 83.5$
$E_t = 0.011116 \times AFUE - 0.098185$

where

 AFUE The annual fuel utilization efficiency (%) Et The thermal efficiency (fraction)
Units Fraction
Input Restrictions As designed
Furnace Fuel Heating Part Load Efficiency Curve
Applicability Systems with furnaces
Definition An adjustment factor that represents the percentage of full load fuel consumption as a function of the percentage full load capacity. This curve shall take the form of a quadratic equation as follows:

(6.7.6-2)

$$Fuel_{partload} = Fuel_{rated} \times F\!HeatP\!LC$$

(6.7.6-3)

$$F\!HeatP\!LC = \left ( a + b \times \frac{Q_{partload}}{Q_{rated}} + c \times \left( \frac{Q_{partload}}{Q_{rated}} \right )^2 \right )$$

where

 FHeatPLC The Fuel Heating Part Load Efficiency Curve Fuelpartload The fuel consumption at part load conditions (Btu/h) Fuelrated The fuel consumption at full load (Btu/h) Qpartload The capacity at part load conditions (Btu/h) Qrated The capacity at rated conditions (Btu/h)

[table title="Furnace Efficiency Curve Coefficients" id="furnace-efficiency-curve-coefficients"]

 Coefficient Furnace a 0.0186100 b 1.0942090 c -0.1128190
Units Data structure
Input Restrictions As designed when data is available, otherwise use the default values are provided above.
Applicability Furnace Fuel Heating Pilot Systems that use a furnace for heating The fuel input for a pilot light on a furnace Btu/h As designed
Applicability Furnace Fuel Heating Fan/Auxiliary Systems that use a furnace for heating The fan energy in forced draft furnaces and the auxiliary (pumps and outdoor fan) energy in fuel-fired heat pumps Kilowatts (kW) As designed

## Electric Heat Pump

Applicability Electric Heat Pump Heating Capacity All heat pumps The full load heating capacity of the unit, excluding supplemental heating capacity at ARI rated conditions Btu/h As designed
Applicability Electric Heat Pump Supplemental Heating Source All heat pumps The auxiliary heating source for a heat pump heating system. The common control sequence is to lock out the heat pump compressor when the supplemental heat is activated. Other building descriptors may be needed if this is not the case. Choices for supplemental heat include: Electric resistance Gas furnace Oil furnace Hot water Other List (see above) As designed
Electric Heat Pump Heating Efficiency
Applicability All heat pumps
Definition

The heating efficiency of a heat pump at ARI rated conditions as a dimensionless ratio of output over input. The software must accommodate user input in terms of either the Coefficient of Performance (COP) or the Heating Season Performance Factor (HSPF). Where HSPF is provided, COP shall be calculated as follows:

(6.7.6-4)

$1) All\ Single\ Package\ Equipment$
$C\!O\!P = 0.2778 \times H\!S\!P\!F + 0.9667$
$2) All\ Split\ Systems$
$C\!O\!P = 0.4813 \times H\!S\!P\!F - 0.2606$

For all unitary and applied equipment where the fan energy is part of the equipment efficiency rating, the COP shall be adjusted as follows to remove the fan energy:

(6.7.6-5)

$$C\!O\!P_{adj} = \frac{\frac{H\!C\!A\!P_{rated}}{3.413} - B\!H\!P_{supply} \times 0.7457}{\frac{H\!C\!A\!P_{rated}}{C\!O\!P \times 3.413} - B\!H\!P_{supply} \times 0.7457}$$

where

 COPadj The adjusted coefficient of performance for simulation purposes COP The ARI rated coefficient of performance HCAPrated The ARI rated heating capacity of a packaged unit (kBtu/h) BHPsupply The supply fan brake horsepower (bhp).

Refer to building descriptor Supply Fan BHP.

Units Unitless
Input Restrictions As designed
Electric Heat Pump Heating Capacity Adjustment Curve(s)
Applicability All heat pumps
Definition

A curve or group of curves that represent the available heat-pump heating capacity as a function of evaporator and condenser conditions. The default curves are given as follows:

(6.7.6-6)

$$Q_{available} = C\!A\!P\_FT \times Q_{rated}$$For air-cooled heat pumps:

(6.7.6-7)

$$C\!A\!P\_FT = a + b \times t_{odb} + c \times \left. t_{odb}\right. ^2 + d \times \left. t_{odb}\right. ^3$$

For water-cooled heat pumps:

(6.7.6-8)

$$C\!A\!P\_FT = a + b \times t_{db} + d \times t_{wt}$$

where

 Qavailable Available heating capacity at present evaporator and condenser conditions (kBtu/h) tdb The entering coil dry-bulb temperature (°F) twt The water supply temperature (°F) todb The outside-air dry-bulb temperature (°F) Qrated Rated capacity at ARI conditions (in kBtu/h

 Coefficient Water-Source Air-Source a 0.4886534 0.2536714 b -0.0067774 0.0104351 c N/A 0.0001861 d 0.0140823 -0.0000015
Units Data structure
Input Restrictions User may input curves or use default curves. If defaults are overridden, supporting documentation shall be provided.
Electric Heat Pump Heating Efficiency Adjustment Curve(s)
Applicability All heat pumps
Definition

A curve or group of curves that varies the heat-pump heating efficiency as a function of evaporator conditions, condenser conditions and part-load ratio. The default curves are given as follows:

(6.7.6-9)

$$P\!LR = \frac{Q_{operating}}{Q_{available}\left ( t_{db},t_{odb/wt}\right )}$$

(6.7.6-10)

$$E\!I\!R\_F\!P\!LR = a + b \times P\!LR + c \times P\!LR^2 + d \times P\!LR^3$$

Air Source Heat Pumps:

(6.7.6-11)

$$E\!I\!R\_FT = a + b \times \left ( \frac{t_{odb}}{t_{db}} \right ) + c \times \left ( \frac{t_{odb}}{t_{db}} \right ) ^2 + d \times \left ( \frac{t_{odb}}{t_{db}} \right )^3$$Water Source Heat Pumps:

(6.7.6-12)

$$E\!I\!R\_FT = a + b \times t_{wt} + d \times t_{db}$$

(6.7.6-13)

$$P_{operating} = P_{rated} \times E\!I\!R\_F\!P\!LR \times E\!I\!R\_FT \times C\!AP\_FT$$

where

 PLR Part load ratio based on available capacity (not rated capacity) EIR-FPLR A multiplier on the EIR of the heat pump as a function of part load ratio EIR-FT A multiplier on the EIR of the heat pump as a function of the wet-bulb temperature entering the coil and the outdoor dry-bulb temperature Qoperating Present load on heat pump (Btu/h) Qavailable Heat pump available capacity at present evaporator and condenser conditions (Btu/h). tdb The entering coil dry-bulb temperature (°F) twt The water supply temperature (°F) todb The outside air dry-bulb temperature (°F) Prated Rated power draw at ARI conditions (kW) Poperating Power draw at specified operating conditions (kW)

 Coefficient Air-and Water-Source EIR-FPLR Water-Source EIR-FT Air-Source EIR-FT a 0.0856522 1.3876102 2.4600298 b 0.9388137 0.0060479 -0.0622539 c -0.1834361 N/A 0.0008800 d 0.1589702 -0.0115852 -0.0000046
Units None
Input Restrictions User may input curves or use default curves. If defaults are overridden, documentation shall be provided.
Applicability Electric Heat Pump Supplemental Heating Capacity All heat pumps The design heating capacity of a heat pump supplemental heating coil at ARI conditions Btu/h As designed
Applicability Electric Supplemental Heating Control Temp All heat pumps The outside dry-bulb temperature below which the heat pump supplemental heating is allowed to operate Degrees Fahrenheit (°F) As designed. Default to 40°F
Applicability Coil Defrost Air-cooled electric heat pump The defrost control mechanism for an air-cooled heat pump. The choices are: Hot-gas defrost, on-demand Hot-gas defrost, timed 3.5 minute cycle Electric resistance defrost, on-demand Electric resistance defrost, timed 3.5 minute cycle Defrost shall be enabled whenever the outside air dry-bulb temperature drops below 40°F. List (see above) Default to use hot-gas defrost, timed 3.5 minute cycle. User may select any of the above.
Applicability Coil Defrost kW Heat pumps with electric resistance defrost The capacity of the electric resistance defrost heater Kilowatts (kW) As designed. This descriptor defaults to 0 if nothing is entered.
Applicability Crank Case Heater kW All heat pumps The capacity of the electric resistance heater in the crank case of a direct expansion (DX) compressor. The crank case heater operates only when the compressor is off. Kilowatts (kW) As designed. This descriptor defaults to 0 if nothing is entered.
Applicability Crank Case Heater Shutoff Temperature All heat pumps The outdoor air dry-bulb temperature above which the crank case heater is not permitted to operate. Degrees Fahrenheit (°F) As designed. This descriptor defaults to 50°F.

## Heat Recovery

Exhaust to Outside Heat Recovery Effectiveness
Applicability Any system with outside air heat recovery
Definition

The effectiveness of an air-to-air heat exchanger between the building exhaust and entering outside air streams. Effectiveness is defined as follows:

(6.7.6-14)

$$H\!R\!E\!F\!F = \frac{\left ( E\!E\!A_{db} - E\!L\!A_{db}\right )}{\left ( E\!E\!A_{db} - O\!S\!A_{db}\right )}$$where

 HREFF The air-to-air heat exchanger effectiveness EEAdb The exhaust air dry-bulb temperature entering the heat exchanger ELAdb The exhaust air dry-bulb temperature leaving the heat exchanger OSAdb The outside air dry-bulb temperature
Units Ratio
Input Restrictions As designed
Applicability Condenser Heat Recovery Effectiveness Systems that use recover heat from a condenser The percentage of heat rejection at design conditions from a DX or heat pump unit in cooling mode that is available for space or water heating. Percent (%) As designed. The software must indicate that supporting documentation is required on the output forms if heat recovery is specified.
Applicability Heat Recovery Use Systems that use heat recovery The end use of the heat recovered from a DX or heat pump unit. The choices are: Reheat coils Water heating List (see above) As designed. The software must indicate that supporting documentation is required on the output forms if heat recovery is specified.