Single Pole vs. Double Pole Thermostat: Which to Choose?

You need to choose the right thermostat for safe and energy-efficient heating and cooling control. But should you get a single-pole or a double-pole thermostat for your home?

Thermostats are an essential part of your HVAC system, and you need to know about a few things before deciding what to buy. And that's why you should learn about the difference between a single-pole and a double-pole thermostat.

And there's more! Keep reading to the end to learn how to install pole thermostats in your home.

What Is a Pole in a Thermostat?

Let's start by discussing an essential component of a single-pole and double-pole thermostat. The pole of a thermostat means separate circuits that a thermostat can operate from.

In a single-pole thermostat, the electrical current powers the device only in one direction, meaning that the circuits can't work separately. As such, you can't turn this device OFF without disconnecting it from a power source.

The electric charge flows in two directions in double-pole thermostats. This means you can quickly turn these thermostats OFF (something single-pole devices can't do).

Low-Voltage vs. Line-Voltage Thermostats: How Do They Work?

 

Thermostats use low voltage and line voltage for heating and cooling control. But what is the difference between a single-pole and a double-pole thermostat?

First, let's see how all thermostats work.

When the heating (cooling) device is ON, the circuit closes the thermostat, allowing the electricity to power the heating element. When the set temperature is reached, the thermostat automatically cuts the electrical current, allowing the heater to cool down. This process repeats in cycles to maintain the desired indoor temperature.

A low-voltage device is wired directly into the control device. These thermostats are cheap and require about 24 Volts to work. Low-voltage thermostats use much less power than line-voltage thermostats, and they are widely used to control:

• Boilers

• Heat pumps

• Heaters

• Furnaces

Line-voltage thermostats work from circuit breaker boxes that provide from 120 to 240 Volts. This is the most popular voltage that you can find in devices such as:

• Ceiling fans

• Lamps

• HVAC systems

A line-voltage thermostat is excellent for most heating and cooling control systems. They usually work without transformers that reduce the voltage. Furthermore, all single-pole thermostats and double-pole thermostats are line-voltage relays.

What Are Single Pole Thermostats?

Single-pole thermostats are line-voltage devices that control the HVAC equipment. Single pole switches are wired directly to the circuit breaker and operate in one direction of the electrical current. These devices maintain a continuous connection between the heater and the electrical panel. You won't be able to turn a single-pole thermostat off like any other electrical device. Single-pole thermostats don't even have an OFF setting. Instead, they have a “low setting”, which usually stands at 45 degrees Fahrenheit (about 7 degrees Celsius). This means that the thermostat will power on the heater whenever the indoor temperature hits the lowest setting.

What Are Double-Pole Thermostats?

Double pole thermostats (also known as four-wire controls) are line-voltage devices that control the heating equipment with two-directional electric currents.

A double-pole thermostat is wired into the circuit breakers just like a single-point thermostat. However, these HVAC thermostats have a real OFF setting that completely isolates them from the HVAC system.

The double pole thermostat won't measure the room temperature and activate automatically in the offline mode. This is a more convenient and energy-efficient solution for most users. And it's always safer when the heating equipment doesn't turn on when you're away from your home.

How to Identify a Thermostat

Seems pretty straightforward so far, right? We have great news. You can identify the difference between a single-pole thermostat and a double-pole thermostat in a few easy steps. 

• Buttons and settings. Unlike their double-pole counterparts, single-pole thermostats have a “low setting” instead of an OFF switch. Therefore, if you can't see a way to turn the device offline — you're looking at a single-pole thermostat.

• Wiring. Check the back of the device after taking it from the wall. Inspect the wiring. A single-pole thermostat has two wires, while a double-pole thermostat will have four wires.

And what if you see more than four wires? In that case, you're looking at a low-voltage thermostat. These devices can't control electric heating equipment and won't have any use for your HVAC system.

Don't detach the device if it's on! Remember to turn off the power supply at the breaker first. Afterward, you can safely disconnect the thermostat from the heating equipment (or the wall) to see its back.

Now, let's see how you can install a thermostat.

Installing a Thermostat

Can you set up a thermostat safely without a professional technician? Yes! Below, we describe how to perform a double and single-pole thermostat installation step-by-step.

1. Turn off the electrical power at the circuit breaker (fuse box). We recommend locking the panel to ensure no one can turn the power on unexpectedly.

2. Remove the cover from the junction box.

3. Leave two heater wires loose by disconnecting the factory connector.

4. Connect the green grounding screw with a supply grounding wire.

5. Wire the heater to the thermostat wiring box. Then connect the thermostat wiring box to the circuit breaker's supply wire.

6. Connect the heater's and circuit breaker's ground wires in the thermostat wiring box.

Single-pole and double-pole thermostat installation processes are slightly different because of the wiring; as mentioned, a single-pole thermostat has two wires, and a double-pole has four wires. 

How to Install a Single-Pole Thermostat

• Connect the hot supply wire (usually black-colored) to the thermostat's hot supply wire (marked as Line or L1).

• Route the second thermostat wire (Load or T2) to the identically colored wire at the baseboard heater.

• Connect the circuit breaker's and baseboard heater's white-colored supply lines.

How to Install a Double Pole Thermostat

• Connect a hot supply wire (it should be black) to the thermostat wire (Line or L1) using wire connectors.

• Route the thermostat wire (Line or L2) to the supply wire (white).

• Connect the thermostat wires (Load or T1) to the heater's black-colored wire.

• Wire the remaining connection (Load or T2) to the heater's white-colored wire.

Now, you still have a few steps left to finish the installation:

• Place all wires into the wiring compartment before mounting the thermostat.

• Connect the thermostat's supply wires to the supply wires in the junction box.

And your HVAC system is ready! You can now turn the power supply on at the circuit breaker.

How to Choose the Right Thermostat for Your Home

So, what's the best type of thermostat for you? Let's look at the difference between a single-pole thermostat and a double-pole thermostat from several perspectives:

• Energy consumption. You can't turn off a single-pole thermostat like a double-pole one. Therefore, a single-pole device will always consume energy, whereas a double-pole thermostat can cut your energy costs.

• Safety. A single-pole device will automatically turn on when the indoor temperature falls below the minimal settings. Consequently, a double pole device is a safer solution, especially if you're on a trip away from home.

• Convenience. And lastly — you can turn double pole thermostats OFF in a second. By contrast, you'll have to manually disconnect the heater from the power line to turn it offline with a single-pole thermostat.

And if you're in a hurry, here's a comparison table between these types of thermostats.

Conclusion

And this concludes our guide on the difference between a single-pole and double-pole thermostat! Hopefully, you now have a better idea of what type of thermostat will work better for you.

Blackhawk Supply offers a wide selection of high-quality thermostats. Check it out and buy today!