Hello All,

I have a LEED project modeling for the baseline of air-to-air heat pump system with electrical auxiliary heat. In G3.1.3.1 of ASHRAE 90.1-2007, the requirement is "The systems are controlled
with multistage space thermostats and an outdoor air thermostat activate
electric heat only on the last thermostat stage and the outdoor air temperature
is 40 oF and below.".

In my DOE2.2 model, the electrical heat is activated only when the outdoor air temperature is below 40 oF. But meanwhile is the air-to-air heat pump system still running or turned off? From the description above we cannot find proof whether it is still running or shut off. I looked up other materials such as the ASHRARE 90.1-2007 user manual or Advanced Energy Modeling For LEED Technical Manual and none mentioned the heat pump is continuously run when the outdoor air temperature is below 40 F.

Does anyone have any good insight on this? Thanks for you help.

Regards,

David