Use the Equations card and create one input, called Tambient, and connect the appropriate output from the weather model to the Equations card. Then define two equations: Equations 2 _On_Cool_ = GT(Tambient,18) On_Heat LT(Tambient,14) Then simply connect these two outputs to the heat pump model. This approach works well if Tambient is unaffected by the heat pump (as it is in this case). If Tambient was instead the room temperature then you should use a thermostat model to avoid iteration issues. Be aware though that this equation based approach will make the heat pumps run constantly whenever the ambient temperature is above 18 or below 14. If you want to only allow operation of the heat pumps when it's above 18 or below 14 then you'll have to use a thermostat model and an Equations card. In that case you would create three inputs: Tambient, WantCool, and WantHeat. You would connect the thermostat to the building and then the thermostat outputs to WantCool and WantHeat equation inputs. Then your two equations would change to: Equations 2 _On_Cool_=GT(Tambient,18)*WantCool _On_Heat_=LT(Tambient,14)*WantHeat Jeff
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