If you are looking to install or repair a double pole thermostat, it's important to understand the wiring behind the device before you begin. Additionally, basic knowledge of what a double pole thermostat is and how it interacts with your HVAC system is essential. Before beginning any electrical work, be sure you have taken certain safety measures for the protection of yourself, your equipment and those around you.

Close-Up Of Thermostat On Wall
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How to Wire a Double Pole Thermostat

What Is a Double Pole Thermostat?

You might wonder what exactly a double pole thermostat is and how it differs from single pole varieties. Both types tend to be controlled by a knob on a wall unit and control heat that is emitted via the baseboards of your home or office. A double pole system has an "off" setting, which can be significant for both safety and energy savings. Though it may seem as if your single pole thermostat has an "off" setting, it actually only has a very low setting, typically around 45 degrees Fahrenheit. When you turn the knob on a double pole thermostat all the way in the counterclockwise direction, however, it is off. This sort of system will not turn on, even when the temperature goes below 45 degrees. This is because double pole thermostats actually interrupt the the current flow of electricity and do not keep voltage on the heater, like their single pole counterparts.

Electricity Safety Basics

Be sure to turn off power to the area where you'll be working at the circuit breaker before you begin your project. Inform anyone who is present that you will be doing electrical work. Ask that they not make any changes to the electricity by flipping the breaker or any switches until you have finished. If possible, wear high-voltage rubber gloves and use insulated tools. If you are ever unsure as to what needs to be done, you should contact a professional rather than proceeding on your own.

Double Pole Thermostat Wiring Diagram

If you plan to to do work to your double pole thermostat or are installing baseboard heaters, you will first need to shut off the power and follow basic electrical safety procedures. Then, remove the thermostat from the wall. It is usually attached to the wall and then with wire nuts to the wires coming from inside the wall. Since you are working with a double pole thermostat, there should be four wires. Two of these are live wires and two are load wires. You can use a voltage detector before you disconnect the wires from the old thermostat to determine which wires are live, if you are unable to determine this by sight. Commonly, line wires are black and load wire are red. If you choose to follow this method, be extremely careful and do not touch the wires with your bare hands.

Once you have determined the live and load wires, you can mark them so that you'll know which are which. Then, remove the old thermostat box.

Install the new thermostat box according to manufacturer instructions. Pull the live and load wires through and attach with wire nuts at the appropriate junction points. Use a voltage meter to test them to be sure they are wired correctly. Again, do not touch wires with your bare hands while power is turned on. Once you have reattached the double pole thermostat to the wall, you can turn the power back on.