Tip & How-To about Heating & Cooling
On a heat pump the difference from heat to cool is the reversing valve.
In cooling or heating the Y1 terminal will always be energized, this is the contactor.
Depending on brand the reversing valve will either be energized in Heat or Cool. At the outdoor unit check to see if the reversing valve is getting 24 volts in cool, if not check to see if it is getting 24 volts in heating. The easiest way to check if the reversing valve is shifting, is to feel the big copper tube, (it is not the suction line on a heat pump) this is a refrigerant vapor line. It will be cold in cooling and hot in heating.
Check your thermostat installation instructions and heat pump installation instructions to determine the proper terminal designations for your heat pump and thermostat. There are some brands out there that use the B terminal as common to the 24 volt circuit, so you have to check the wiring and make sure this is not common.
If it is energized in Cool then the Y1 and O terminal will be energized. You will have 24 volts from common usually the C terminal to Y1 and O.
If it’s energized in Heat then the Y1 and B terminal should be energized. You will have 24 volts from common usually the C terminal to Y1 and B.
If you get heat when you’re calling for cooling or vice versa then switch the wire between the B and O terminals.
Posted by Bill Long on
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