Electric Heat Pump Heating Capacity 


Applicability 
All heat pumps 
Definition 
The full load heating capacity of the unit, excluding supplemental heating capacity at ARI rated conditions 
Units 
Btu/h 
Input Restrictions 
As designed 
Baseline Rules 
Autosize and use an oversizing factor of 25% (let the software determine heating capacity based on the building loads). The equipment capacity may need to be increased to ensure that the number of unmet load hours do not exceed 300. 
Electric Heat Pump Supplemental Heating Source 


Applicability 
All heat pumps 
Definition 
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:

Units 
List (see above) 
Input Restrictions 
As designed 
Baseline Rules 
Baseline electric airsource heat pumps shall be modeled with electric auxiliary heat and an outdoor air thermostat. The systems shall be controlled to energize auxiliary heat only when the outdoor air temperature is less than 40°F. The airsource heat pump shall be modeled to continue to operate while auxiliary heat is energized. 
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). The ARI ratings include the energy of the supply air fan. 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:
When COP_{47} is given (Equation 3.7.64) $$COP_{nfheating}=1.48\times 10^{7}\cdot COP_{47} \cdot Q +1.062 \cdot COP_{47}$$When HSPF is given (Equation 3.7.65) $$COP_{nfheating}=0.0296\cdot HSPF^{2} + 0.7134 \cdot HSPF$$
where


Units 
Unitless 

Input Restrictions 
As designed 

Baseline Rules 
The heat pump efficiency for baseline systems 2 and 4 shall be determined from the data below.

Electric Heat Pump Heating Capacity Adjustment Curve(s) 


Applicability 
All heat pumps 

Definition 
A curve or group of curves that represent the available heatpump heating capacity as a function of evaporator and condenser conditions. The default curves are given as follows: (Equation 3.7.66) $$Q_{available} = CAP\_FT \times Q_{rated}$$ For aircooled heat pumps: (Equation 3.7.67) $$CAP\_FT = a+b \cdot t_{odb} + c \cdot t_{odb}^{2} + c \cdot t_{odb}^{3}$$ For watercooled heat pumps: (Equation 3.7.68) $$CAP\_FT = a + b \cdot t_{db} + d \cdot t_{wt}$$ where


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 heatpump heating efficiency as a function of evaporator conditions, condenser conditions and partload ratio. The default curves are given as follows: (Equation 3.7.69) $$PLR  \frac{Q_{operating}}{Q_{available, (t_{db},t_{odb/wt})}}$$ (Equation 3.7.610) $$EIR\_FPLR = a + b \cdot PLR + c \cdot PLR^{2}+ d \cdot PLR^{3}$$ Air Source Heat Pumps: (Equation 3.7.611) $$EIR\_FT = a + b \cdot t_{odb} + c \cdot t_{odb}^{2}+ d \cdot t_{odb}^{3}$$ Water Source Heat Pumps: (Equation 3.7.612) $$EIR\_FT = a + b \cdot t_{wt} + d \cdot t_{db}$$ (Equation 3.7.613) $$P_{operating} = P_{rated} \times EIR\_FPLR \times EIR\_FT \times CAP\_FT$$ where


Units 
Data structure 

Input Restrictions 
User may input curves or use default curves. If defaults are overridden, documentation shall be provided. 

Baseline Rules 
Use default curves 
Electric Heat Pump Supplemental Heating Capacity 


Applicability 
All heat pumps 
Definition 
The design heating capacity of a heat pump supplemental heating coil at ARI conditions 
Units 
Btu/h 
Input Restrictions 
As designed 
Baseline Rules 
Autosize 
Electric Supplemental Heating Control Temp 


Applicability 
All heat pumps 
Definition 
The outside drybulb temperature below which the heat pump supplemental heating is allowed to operate 
Units 
Degrees Fahrenheit (°F) 
Input Restrictions 
As designed. Default to 40°F 
Baseline Rules 
The space is required to be controlled with multistage space thermostats and an outdoor air thermostat which would energize the auxiliary heat on the last thermostat stage and when the outdoor air temperature is less than 40°F 
Coil Defrost 


Applicability 
Aircooled electric heat pump 
Definition 
The defrost control mechanism for an aircooled heat pump. The choices are:
Defrost shall be enabled whenever the outside air drybulb temperature drops below 40°F. 
Units 
List (see above) 
Input Restrictions 
Default is to use hotgas defrost, timed 3.5 minute cycle. User may select any of the above. 
Baseline Rules 
The baseline building uses the default. 
Coil Defrost kW 


Applicability 
Heat pumps with electric resistance defrost 
Definition 
The capacity of the electric resistance defrost heater 
Units 
Kilowatts (kW) 
Input Restrictions 
As designed. This descriptor defaults to 0 if nothing is entered. 
Baseline Rules 
Not applicable. 
Crank Case Heater kW 


Applicability 
All heat pumps 
Definition 
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. 
Units 
Kilowatts (kW) 
Input Restrictions 
As designed. This descriptor defaults to 0 if nothing is entered. 
Baseline Rules 
Zero (0) 
Crank Case Heater Shutoff Temperature 


Applicability 
All heat pumps 
Definition 
The outdoor air drybulb temperature above which the crank case heater is not permitted to operate. 
Units 
Degrees Fahrenheit (°F) 
Input Restrictions 
As designed. This descriptor defaults to 50°F. 
Baseline Rules 
50°F 