Thermostat Wiring Diagrams – Heat pumps are wired for HVAC control far differently than air conditioning systems so make sure you know the difference and correctly identify the type of HVAC system you have installed.
Thermostat Wiring Diagrams
With the top diagram showing an air conditioning system and the second diagram showing a heat pump system and finally the third diagram showing the average type of split system with an air conditioner or gas or oil furnace used for heating. The heating system could also be a boiler, however, is it necessary to ensure with split systems and the type of heating systems described that you do not have dual transformers in the system or to at least be aware that the system has dual transformers. Whenever in doubt call a professional.
Thermostat Wiring Diagrams - HVAC Control - Heat Pump Systems
Heat pumps are different than air conditioners because heat pumps use the process of refrigeration to heat and cool. While an air conditioner uses the process of refrigeration to only cool the central air conditioner will usually be paired with a gas furnace, an electric furnace, or some other method of heating. So while the air conditioner is used extensively in warm or hot weather the heat pump is used year round. The heat pump system has different controls than an air conditioner, it has its own heat pump sequence of operation so a heat pump works differently than an air conditioner so will require a different thermostat and different wiring than an air conditioner. Sometimes, depending on the thermostat and the manufacturer, the thermostat can be a dual heat pump thermostat or it can be used for an air conditioner and gas furnace system depending on how the thermostat is wired. Always make sure you know what type of system you have before doing any wiring.