The thermostat is a temperature regulating device. At first, you need to set your required temperature and then the system automatically adjusts the temperature by switching heating or cooling devices on or off. The operating system is very easy, but the installation or wiring procedure is not that much easy without any instruction. You can call a professional anytime, but if you want to do the job by yourself, then you need to know some important things. Here I’m going to help you with that tricks.
The location is a very important factor for the thermostat. Before wiring, you need to select the right place to set. Locate your room thermostat at about chest height on an interior wall, in the living room, in the dining room, or in a place where the natural air can circulate. Avoid locating it on an exterior building wall, in direct sunlight, in the kitchen, in the boiler room, behind furniture, or behind any curtain, etc.
Do not forget to check the catalog to know the facilities and functionalities of the thermostat before purchase. Pay attention to the following:
- Cooling, heating or both: The thermostat controls only air conditioning, or a heating system, or both.
- Temperature sensor: there are some older wall thermostats which are using a bi-metallic strip and a mercury bulb to activate the thermostat. On the other hand, modern thermostats use a thermistor or another device.
- C-wire: There are many smart thermostats which do not require C-wire. If there is no C-wire in your system, then choose from them.
- Display type: Check whether the display is analog or digital.
Colors and Terminals
The following descriptions are of the common colors, and your system may use different colors.
- Red color (R terminal) – The R terminal is the power, it comes from the 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 the second 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 selected for this wire, but in general, Black or Blue is used in some thermostats.
- Orange or dark blue color (O or B terminal) – This wire connects to the outside heat pump condenser where the reserving valve is placed. Most of the manufacturers use the orange wire for reversing valve, but Rheem and Ruud utilize the blue wire for reversing valve.
- E Terminal – There is no selected color for this terminal. It is used for heat pumps and stands for Emergency Heating.
- X or Aux terminal – Color is not determined for this terminal, and it is for back-up on a heat pump. It allows for auxiliary heating and locates in the air handler.
- S1 & S2 Terminal – These terminals is used for the Outdoor temperature sensor. These wires are completely different from the other thermostat wires, and they have shielded You may find them as T terminal in some thermostats.
How to wiring a thermostat
You may want to replace your thermostat with the latest one, and you are using HAVC system then follow the following instruction. But if your system is other than HAVC then it’s better to call a professional to avoid any risk.
- 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 the mechanical Mark the holes where the screws will go into the wall.
- Drill the mounting holes and insert the wall anchors in them. 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.
- To avoid the risk of insulation nicks, shorts, and cuts of old wiring, it’s better to use new wires.
- Avoid using the thermostat power transformer for doorbells or any other devices.
- Must seal the hole of the building wall which is used for the thermostat wires passing out to the thermostat mount.
- When setting the thermostat on the wall, make sure that it is level; otherwise, the mercury switch will not keep the proper temperature settings especially for the mechanical thermostat.
- Do not forget to switch off the power and confirm that it is off before wiring a thermostat.
- Read the installation guide carefully before going to the action.