Wiring a thermostat is not so difficult if you have a specific guideline. At first you should know what type of system you have in your home because the wiring systems are not same for all. It is better to call a professional for working in a Heat Pump system, a multi-zone system, a regular split-system AC and a boiler for heat, or an Apollo based system with a split AC system. Those systems are very complex to deal with, and may require special sub-bases to work properly with thermostat control circuit. There are different controls, and multi-colored thermostat wires for the controls run into the thermostat for Heat-pump system. The main problem is to dealing with the different colored wires, you need to identify them with some numbers and letters. Each wire need to go to the correct terminal on the thermostat, otherwise the unit will not run accurately.
How to Wire a Thermostat
Before wiring, please read the thermostat installation directions, it will help you to overcome the simple installation problems. Here I’m going to guide you regarding how to wire a thermostat with HVAC system. Turn off the power before starting to install and ensure that you are getting enough light to do the job smoothly. Make sure that the power of the heating and cooling unit at the circuit breaker is off but the thermostat is turned on.
How to adjust the heat anticipator
Be aware whether your thermostat is equipped with heating and cooling anticipators, or not. In mechanical thermostat, cooling anticipator is non-adjustable, but heat anticipator is adjustable. For the heating system, the heat anticipator setting is more important. In the mechanical thermostat, there is a little adjuster tab in the middle of it. You will get it after pulling off the front cover of the thermostat. It is the heat anticipator, which is indicating a number. If you are changing your mechanical thermostat with another mechanical thermostat, then you need to adjust the heat anticipator as same. So, do it manually right now. If you are replacing with a digital thermostat, then it will adjust automatically.
Meaning of the Colors and Terminals
After unscrewing the thermostat from the sub base, take note of each wire. Do not get confused if the color does not match with this guideline; make sure you mark the wires with the masking tape.
The following descriptions are for the common colors and your system may use different colors.
- Red color (R terminal) – The R terminal is the power, it comes from transformer. There can be two separate wires, introduce as RH and RC terminals. RH terminal is selected for the power of heating and RC is for the power of cooling.
- Green color (G terminal) – This terminal is used for the fan relay to energize the indoor blower fan.
- Yellow color (Y terminal) – This is forcooling or air conditioning and connects to the compressor. There can be another terminal indicated as Y2, which is for cooling second stage. If you have two compressors and need second stage cooling in your system, then this terminal is necessary.
- White color (W terminal) – This is the terminal for heating, which connects directly to the heating source such as gas or oil furnace, electric furnace, orboiler or auxiliary heating for a heat pump. W2 terminal is used for second stage heat. If there are gas furnaces with low and high fire, and demands control from two stage heating, then it is required.
- Black or Blue color (C terminal) – The C or Common wire originates from the transformer, which is important to complete the 24 volts power circuit in the thermostat. There is no universal color is selected for this wire but in general, Black or Blue is used in some thermostats.
How to remove and adjust the Wires
Ensure that the power is off and remove the wires from the terminals on the sub-base. Pull the wires a bit to check if there are more wires behind the wall. Unscrew the sub-base from the wall and wrap the wires around the pencil or pen to keep them from falling back to the wall.
Take the new sub-base and put on the wall. Make sure that it is level; otherwise the mercury switch will not keep the proper temperature settings especially for mechanical thermostat. Mark the holes where the screws will go into the wall.
Drill the mounting holes and insert the wall anchors in them until the lips of the anchors remain visible. Now unwrap the wires from the pencils or pens and run them through the center of the sub-base. Screw the sub-base properly and ensure that it is level.
Attach each wire to the terminal by using the color code of the thermostat wires. If the color codes do not match, use the color as you have marked with the masking tape. Attach the thermostat to the sub base and tighten the built-in screws or snaps onto the sub-base. Fasten the front cover of the thermostat and restore the power. Check the heating and cooling systems are turning on or off perfectly and all the features are working properly. If everything is ok, then cheer up.Related posts: