I am considering installing a Generac 22kW whole house generator and automatic transfer switch. The transfer switch is designed to shed the Carrier Infinity heat pump if the start up load is more then the generator can handle. When power curtailment is in use, a "Curtailment Active" message is displayed on the controller screen.

Normally, the automatic transfer box is wired to the thermostat (controller) to shed the heat pump however, the dealer who installed the heat pump is adamant the Carrier Infinity controller should NOT be rewired to accommodate the generator "shed" feature. He feels doing so could disrupt data storage information.

Carrier Infinity heat pump components are controlled through a wall mounted Infinity Control. The control replaces the conventional thermostat and provides a single wall control for controlling all features and system settings including cooling temperature, heat temperature, humidity, multi stage compressor settings, etc.

The Carrier Infinity controller on my heat pump also stores 27 different codes to identify faults with the system over time. The controller communicates operating conditions and other data that is passed continually between the various components over the ABCD bus. All Infinity fan coils are variable speed and the compressor is multi stage.

Approximately two years ago, the utility company discontinued the curtailment program, so the terminals on the compressor control board are no longer in use.

If the Generac automatic transfer switch uses a NC relay and I believe it does, it seems to me I could use terminals R and Y2 located on control board to shed the heat pump just as Carrier intended the terminals to be used by the power company.

Do you think it would be appropriate to use the two curtailment terminals on the compressor control board to shed the compressor? Using these terminals would not shed the air handler blower motor.

  • 1
    What is "data storage information"? – longneck Apr 20 '15 at 16:24
  • @longneck -- thermostat programming, I bet – ThreePhaseEel Apr 21 '15 at 0:00
  • What is Data Storage information? The controller stores codes (along with other information) that help identify system faults. – user62033 Oct 31 '16 at 15:19
  • What is the model number on the ATS? – ThreePhaseEel Nov 1 '16 at 12:25

I'm with Billy, I see no problem. Here are my concerns: You are not really needing to break R from Y2. You are breaking Y2 from Y2. The red will stay where it is to power all other features. And why is the heat pump second stage? Unless the reversing valve is stage one. And what is the back-up heat? If it is electric resistance, that will require a whole lot more power then the heat pump. That would be where you would want to shed load. With 22-KW of generator, what is the tonage of the heat pump. 22-KW can start a lot of heat pump.


Do you think it would be appropriate to use the two curtailment terminals on the compressor control board to shed the compressor?

Yes. If it was OK for your utility company to use those terminals in the past at their discretion to shed load, then it is ok for your generator to use those terminals for the same purpose.

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