Disable Goodman Heat Pump Compressor

czars

I want to disable a Goodman Heat Pump compressor when the outside temperature goes below 35 degrees F (heat strips are on) by interrupting the thermostat signal commanding to the outside unit to run. Can I just interrupt the 24 VAC to the outside unit?

flashheatingand

You can, with an outdoor t-stat wired in series to the low voltage circuit. Otherwise, you can manually switch it at your indoor t-stat, by manually switching to emergency heat.

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czars

Is it acceptable to use the external T-Stat to interrupt the 24VAC going to the outside unit?

DuMass

That is something that can be done easily with a better quality thermostat, like the HW VisionPro along with their optional OD temp sensor. You can program it for compressor lockout below a certain OD temp and run only the aux heat strips. You can also program it to lockout the aux heat strips when the outdoor temp rises above a certain point.
When the OD temp is in between these two set points, the system operates normally with compressor and aux heat strips as needed.

beenthere

Just interrupt the Y terminal.

Don't know why you would want to shut off the heat pump at 35 though, its still cheaper then just using the strip heaters at that temp.

Doc Holliday

I was thinking the same thing. Completely defies the purpose of having a heat pump.

user84377

You should never lock out your heat pump compressor until you are well under the system balance point. This is the point at which you are picking up as much heat from outdoors as the home is giving up to the outdoors. You would still want to run the compressor until you are well beneath that balance point as the system is still picking up heat, the heating strips (aux) is merely supplemental unless the system has been sized for the heater to be the sole provider of heat. If you are thinking of saving money this way..it is possible providing your KW per hour is pretty cheap and the heaters are able of efficiently taking the load. If you are thinking of doing this b/c you are annoyed by the "cold" heat at lower temperatures...well, can't blame you for not liking that. We do not even suggest TRADITIONAL heat pumps in cold climates. TRADITIONAL heat pumps are great for moderate climates.

If you are using an older mechanical stat or even a digital stat that is not properly set up..........you can remedy the "cold" heat syndrome many comlain about at lower ambient temperatures by installing a GOOD digital stat that can sense outdoor temperature and when set up properly they will along for longer system run at colder outdoor temps plus you can set the point at which your electric heaters come on. Many times with the mechanical stat, cheaper digital stats, or improperly set up stat you can experience what is calling floating...where your heat pump simply runs and runs (typically would occur around balance point) without ever getting to the "trigger" point to bring heat strips on and without being able to satisfy the setpoint. So it runs, runs, and runs some more. There is a good article at http://hvacmarket.com/cgi/wp regarding thermostats....sorry I do not have the direct article link...it is in there somewhere.


Using the correct Honeywell visionpro stat, you can use an outdoor sensor at the unit and setting the stat up for the application you can do just that.