If you will be installing a White-Rodgers thermostat, new heat pump or replacing any parts within the larger HVAC system, it may become necessary to learn how to properly connect wires to either the thermostat, the heat pump or both. Before undertaking any electrical work, it's essential that you understand all of the steps required throughout the process. In addition, basic safety procedures must be followed.
Electrical Work Safety Basics
Before beginning any work with electricity, it's essential that you turn off power to the area where the circuit breaker is. If anyone else is present, let them know that you will be doing electrical work, and ask that they not flip the breaker or turn on any switches until you have finished. Whenever possible, wear high-voltage rubber gloves and use only tools with insulated handles. Contact a professional rather than proceeding on your own if you are unsure exactly what you should be doing.
White-Rodgers Thermostat Wiring
If you have a White-Rodgers heat pump and thermostat system, or an Emerson thermostat, the wiring likely follows a particular pattern. If you are installing a new thermostat, refer to the manufacturer's instructions. They should contain a diagram of the wire terminals and indicate which wires go where. New thermostat units may even come with labeled wires for easy installation.
Most White-Rodgers thermostats have three or four terminals for connecting wires. These are likely labeled 'RC,' 'RH' and 'O/B.' The first of these deals with the air conditioning, and 'RH' is related to the heat. The last terminal may also be labeled as 'Y,' or there may be both a 'Y' and an 'OB' terminal. If there is no wire that corresponds to the last terminal, your system likely has no air conditioner or heat pump. If you have a 'Y' terminal but no 'OB,' you probably have a single-stage air conditioner. If you have both 'Y' and 'Y2' but no 'OB,' you have a two-stage air conditioner. A wire for 'Y' and 'OB' means you have a single-stage heat pump, while that combination plus 'Y2' means a two-stage heat pump.
If you are dealing with a system connected to a heat pump, you will not only need to connect wires to the thermostat terminal properly, but you will also need to use the appropriate setting on the thermostat itself. For systems that have a single-stage heat pump, use setting HP1. Two-stage heat pumps require an HP2 setting.
Connecting Wires at the Heat Pump
If you will be replacing your heat pump or making other repairs, it's always a good idea to take a picture of the wiring before you unhook anything. This can help with connecting the wiring later.
Generally speaking, most HVAC systems rely on a system of color coded wires that you can use to determine which wires go into which terminals. In most cases, 'R,' 'Rc' and 'Rh' connect to the red power wires. A blue or black wire is meant to be connected at a terminal marked 'C,' while a white wire should connect at terminal 'W.' The wire for terminal 'E' is usually a brown one, and 'Y' and 'Y2' are usually yellow. A wire for terminal 'G' is typically green, while 'O' is orange and 'B' is blue. Refer to the manufacturer's instructions for your specific unit to verify these connections if possible.