Thermostat Wiring Diagram with Air Conditioner, Fan, Heat Pump

Hey, today we are going to see Thermostat Wiring Diagram. Here you will find the basics wiring diagram of thermostat with Air Conditioner, Heat Pump, and Blower Fan. The thermostat is very useful devices for HVAC installation in our house. Electronic Engineering makes our daily life more and more relaxable. Temperature control using Thermostat is one of the best examples.

The thermostat is basically a temperature control switch. It goes ON and OFF according to the temperature condition. Basically, it has the bimetallic strip and gas-filled bellows inside it. Anyway, let's go to our main topic that is a simple thermostat connection.

Wiring Diagram of Thermostat

Here we have taken a Four Wire Thermostat. It is the simplest thermostat which can be installed at home. 
As you see in the below diagram the thermostat has four terminal and they are different colors such as Red, White, Yellow, Green.

First of all, let's find all terminals,
  • Red - For Power input.
  • White - For Heating Enable
  • Yellow - For Cooling Enable
  • Green - Control the Fan

Thermostat Wiring Diagram, wiring diagram of thermostat

Remember that the above diagram is the control diagram. That is why the whole circuit is connected to 24V AC. The main AC supply(230V) is to be given separately to the  A/C, Heat Pump, and Fan.

1. Here a 24V Transformer is used to provide the 24V AC to the whole circuit including Relay, Contactor, etc.

2. The terminal 'R' of the thermostat is connected to the transformer power supply.

3. The "W' terminal is connected to the heat pump for heating purpose.

4. The 'Y' terminal is going to the Air conditioner. Actually, this terminal is not directly connected to the air conditioner. It is connected to the Contactor which turns On and OFF the A/C according to the signal comes from the Thermostat.

5.  The 'G' terminal is connected to the blower fan inside the air handler. This fan is used to circulate the hot air and cold air.

6. Here the blue wire is the common wire for all loads i.e. Blower Fan, Heat pump, A/C, etc.

According to the temperature condition inside the room, the thermostat creates signals and feed to the heat pump, A/C, fan, etc. Thus the thermostat maintains a desired temperature inside the room.

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Thermostat Wiring Diagram with Air Conditioner, Fan, Heat Pump Thermostat Wiring Diagram with Air Conditioner, Fan, Heat Pump Reviewed by manoranjan das on 5/18/2019 Rating: 5
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