Nest thermostat wiring diagram heat pump wiring diagram is a simplified up to standard pictorial representation of an electrical circuit. These two connections will ensure that there is power to the thermostat that you are operating.

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Heat pump thermostat wiring diagram. C is known as the common terminal. Heat pump thermostat wiring chart diagram. Before uninstalling the old thermostat take a picture of the wiring with your cell phone before removing the wires. This diagram shows what each terminal designation that goes to the hvac system. Finally the illustration below is for a system with a single transformer. Heat pump thermostat wiring a typical wire color and terminal diagram.
Ac heat pump with standard air handler and single stage electric backup heat standard heat pump thermostat heat pump condenser 24 volt fan only operation common air conditioning heat pump reversing valve electric backup heat low voltage connection some ac systems will have a blue wire with a pink stripe in place of the yellow or y wire. As shown in the diagram you will need to power up the thermostat and the 24v ac power is connected to the r and c terminals. It corresponds to the chart below to explain the thermostat terminal functions. It shows the components of the circuit as simplified shapes and the power and signal contacts amid the devices. The basic heat pump wiring for a heat pump thermostat is illustrated here. The o terminal in this diagram is for use for a heat pump thermostat installation for the reversing valve.
A heat pump thermostat will use the orange wire for the reversing valve in the condenser. The color of wire r is usually red and c is black. This way you have a reference.