Thermostat how many wires

Product Resources. Need more help? Get in touch with our support team. Support hours Monday to Friday 8 a. Type of system. Minimum wires needed. PEK compatible? Heat-only boiler or heat-only furnace. Forced-air furnace 1 stage heating, 1 stage cooling. Heat pump with 1 stage of auxiliary heat.

Dual-transformer system boiler with air conditioning. With the basic Honeywell thermostat, you will find:. We just need to get a grip of what each color wire is and what it does. What does the C wire do? C wire is connected to the transformer and completes the 24V electric circuit.

Newer thermostats have a continuously looped 24V circuit; in older models, the loop is completed only when the power is required when you turn the AC on, for example.

They originate in the transformer air conditioners; in the air handler and provide the hour volt AC power. All air conditioner thermostats have a red wire for power. You may also have Rc or Rh terminals for dual transformer systems; these are special cases in thermostat wiring.

White wires are for heating. W wires go directly to the source of heating; that may be a furnace gas, electric, oil, you name it or heat pumps mini-split heat pumps included. W2 is designated for two-stage heating. Most heat pumps include second-stage heating and require the white W2 wire. Most bigger heat pump manufacturers like Trane, Goodman, Lennox, and so on have the orange wire that goes to the condenser located in the outdoor unit of heat pumps.

Some producers like Rheem energizes the reversing valve when the heating mode is on in heat pumps. Green wire is for the fan. Y terminals are for the connection to the compressor relay. It most often wires to the air handler indoor split-system unit. Y1 is for ordinary or one-stage cooling; this is what most of us have at home. This terminal is only required if you have:. Some other terminals that rarely get used at all the ones on the right side of the thermostat.

In the future, we plan to create a separate article details that the specific function all of them have. Do keep in mind that with so many different thermostats, each wire code can have a different color wire. If a technician that installed your thermostat used a different color, you might have a problem reconnecting the wires. First of all, make sure you will be able to correctly wire the new thermostat. HVAC technicians know the color-coding by heart; they can just remove any Honeywell thermostat, replace it with the new one and reconnect the terminals.

If you unscrew the terminals and remove the wires right away, you may have problems reconnecting the wires to the new terminal. Make sure you have a picture of how the wiring to the old thermostat looks like before continuing. The thermostat holds the wires out of the wall; the wires are suspended on the thermostat. If you remove the thermostat right away, the wires will be lost inside the wall. You will have to either:. To prevent these two scenarios, make sure to spread the wires. Take each wire and bend it outwards.

After you remove the old thermostat, take the new thermostat are put it in the exact same place as the old thermostat. The wires you have fixed on the wall have to be pushed through the hole in the new thermostat. Now you start reconnecting the wire by wire. Having a photo of the old thermostat is very helpful here. There are two ways of how to know where each wire goes:. If you are going by color codes, you can check what each wire means in the section above.

To reconnect the wire, simply put the wire on the right terminal and tighten down the set screw. Pull a wire a bit to make sure the wire is properly fixed.

If the old thermostat has been removed, then the approach is a bit more complex but can still be a DIY project. Note: Your system might not use all the wires in the bundle. This is common and not a problem. Unused wires are usually twisted together and wrapped around the other wires to prevent bare wiring from contacting any bare section of wire being used or a terminal.

If the thermostat has been removed, your job is a bit more complex. One of two approaches might work. Note: As we said above, your system might not use all the wires in the bundle. It depends upon the original installer having used the traditional wiring color code to when installing the thermostat. Note that wiring colors have no inherent meaning. The wires are all the same: solid copper wire covered with colored PVC insulation. The technician will check the connections in the furnace or air handler and complete the wiring of the thermostat.

The C wire delivers constant power to the thermostat, so that it constantly monitors the indoor temperature and other climate features. The purpose of this is to create the most precise indoor comfort.

Many thermostats function without a C wire by periodically pulling power from one of the other wires, usually the red wire. However, if your thermostat information says a C wire is required, then this information is for you.