Dear experts,
?
how can I modulate the COP of a heat pump in eQUEST in relation to outdoor dry bulb temperature, outdoor wetbulb temperature and partial load.?
I see that I can enter the value for electricity input ratio (BTU/BTU)? in a box (e.g. 0.3) and there are two different fraction curves available which
can be defined as linear or quadratic or else functions. But it is unclear to me how these curves are linked to the EIR value (e.g. EIR x frac1 x frac 2 ?)
and furthermore, how the supplemental heater could be considered. I have this problem with the baseline case for a LEED project and the reviewer has
sent to me the following comment:

It is unclear if the packaged rooftop heat pumps in the Baseline model were modeled according to Section G3.1.3.1, which requires that the electric
airsource heat pumps are modeled with electric auxiliary heat that only energizes on the last thermostat stage and when the outdoor air temperature
is less than 40 degrees F. Per ASHRAE Interpretation 90.1-2007-09, this means that the heat pump and auxiliary heat should operate together at low
temperature conditions, with the compressor as the lead machine. The outside air cutoff temperature for the compressor must be no greater than the
temperature associated with the low-temperature heating efficiency requirements of Table 6.8.1B (17 degrees F). Note that for packaged heat pump
units smaller than 65,000 Btuh and packaged terminal heat pumps, the HSPF rating accounts for electric auxiliary operation, and includes test
conditions at 17 degrees F.

The interesting aspect is that there is no cop curve specified in ASHRAE 90.1. There are only two different values for the COP defined (3,3 and 3,22).
So it seems that for the reference model (baseline) the value could be set to constant and I just have to consider three different situations:

toutdb < 17 F --> COP = 1
toutdb = 17 F --> COP = 2,25
toutdb > 40 F --> COP = 3,3

Is this true ? How should I model that in EQUEST ? Any friendly advise is welcome.

Thank you in advance and with best regards

Matt