Hello all. After fighting with eQUEST (and losing), I'm looking for ideas to solve my issue:

I have an air cooled chiller serving a cooling loop which serves fan coils for cooling only. I also have an air-source heat pump as my primary heating plant (with gas boiler as backup). My problem is that my cooling plant will not turn on when the ASHP is created.

I had modeled my heating as a hot water loop with gas boiler only (had not included the ASHP yet). I modeled my cooling loop and cooling plant and everything was working as intended. Then I changed my heating water loop to a two-pipe loop and added my air source heat pump to it:

? chiller type: Heat Pump

? Chilled water loop: Heating Water Loop (the two pipe loop)

? Condenser: Air cooled

I then set my two pipe loop to Snap, with an outdoor snap temperature of 140?F (which will never happen here, effectively making it a heating only loop).

My ASHP works well, everything looks good, except that my cooling plant now does not run at all. :(

I removed my ASHP and made my heating water loop a hot water loop again and the cooling plant runs again.

I can only guess that with multiple cooling loops, the addition of a two pipe loop that is always in heating is somehow preventing my cooling plant from turning on, despite them being totally separate.

I have tried to force the issue by creating equipment controls specifically telling each loop what equipment to use, but to no avail. At this point I am probably going to either model my air cooled chiller as individual DX units in the systems served by the cooling loop, or create an electric boiler with an efficiency equal to the annual heating COP I get from a run with my ASHP running. I think the second option would be more accurate, but I'd rather have it all in one model.

So... has anyone come across this and if so what is the magic little detail that I'm missing? Other ideas?

Many thanks,

Riley Beise, P.Eng., BEMP, LEED Green Associate