Single pole vs double pole: what's the difference?


Wondering about the difference between a single pole thermostat and double pole thermostat? The way a thermostat is wired to your house and heaters plays a role in the reliability and performance of your whole heating system. While the different wiring systems predate smart technology, this is important information to know if you’re considering a smart upgrade.  

Some smart thermostats (Nest & Ecobee) help regulate central heating systems, like a furnace. These are known as low-voltage systems. These systems are found in the majority of households in the northern USA and Canada. 

However, many homes use electric heating like baseboard heaters and other electric space heaters. These are known as line-voltage or high-voltage heating systems. Traditionally, line voltage heating is controlled in two different ways: single pole thermostats or double pole thermostats. Let’s explore this further. 

How Line-Voltage Thermostats Work

The first and simplest way to control line voltage heating is a single pole thermostat. 

Single Pole Thermostats 

A single pole thermostat has a singular switch that opens or closes the heating circuit. Opening the circuit stops power flow to the heater. While closing the circuit lets power run to the heater, so it can regulate room temperature. This is how a thermostat reaches its setpoint. 

A voltage from the electrical panel’s L2 or neutral (N) wire is still present at the heater when a thermostat is in open (or ‘off’) state. But, no current (and thus power) is being produced in this condition. 

single pole thermostat diagram

Typically, any non-dial based single pole thermostat uses a power stealing system. This makes installation easier, since the thermostat only has two interchangeable wires. However, this does have some downsides.  

The most significant drawback is that two-wire single pole thermostats will occasionally have to switch the heater on or off to keep the thermostat itself powered. This means single pole thermostats do not have a fully ‘off’ setting. So, the thermostat may heat a room slightly when not wanted, which reduces energy efficiency. Single pole dial thermostats also have a minimum temperature setting, but do not employ power stealing.

Another disadvantage is that a single pole thermostat may have to turn a heater off periodically when not wanted. This reduces the heater’s output and, ultimately, the comfort of your home. 

Double Pole Thermostats 

The other option for regulating a line voltage heating system is using a double pole thermostat, also known as a two-pole thermostat. 

Double pole thermostats require at least four wires, which can make installation slightly more complex. But, your heater can be completely disconnected from your electrical panel, which isn’t possible with a single pole thermostat.

Since the thermostat has a dedicated L2 (N) connection to power itself, power stealing is not required. So, double pole thermostats have a true ‘off’ setting. This increases energy efficiency and comfort, since no power stealing is needed to run the thermostat. Dial-based double pole thermostats also have an ‘off’ setting.  

Note: Some electrical installations may require a double pole thermostat. So, it’s not recommended to replace a double pole thermostat with a single pole device unless directed by a qualified electrician.

double pole thermostat diagram

Thinking About a Smart Thermostat? 

When considering a smart thermostat, there's no one-size-fits-all solution, since power setups differ from home to home. So, it’s very important to choose a product that’s compatible with your home. 

For example, if you have line voltage heating, Mysa is a smart thermostat that was specifically designed for this type of system.

With a smart thermostat, you get full control of your home’s heating. You can control your thermostat from just about anywhere, set custom thermostat Schedules, and use a ton of other smart features via a smartphone app. Many also integrate with smart home assistants like Apple Homekit, Google Home, and Amazon Alexa

Mysa’s Hardware 

In terms of hardware, Mysa was designed to use the best aspects of the traditional line-voltage power setup. It's a single pole thermostat, since it only switches one panel wire connection to the heater. However, unlike most other single pole thermostats, it requires a L2 (N) connection. So, more than two wires are needed for installation. And unlike a two-wire power stealing thermostat, Mysa has a true ‘off’ setting. This means better energy efficiency and comfort. 

Compatibility with Mysa

Mysa can likely replace any line-voltage thermostat up to 3800 W at 240 V or 1900 W at 120 V or less. But, it is best to check compatibility here before making a purchase. 

Single vs Double Pole 

So, that’s the difference between single and double pole thermostats for line voltage heating systems. Upgrading to a smart thermostat comes with a lot of benefits, however, it’s first important to know what kind of heating system and thermostat you have. 

If you have any questions about thermostat compatibility or installation, feel free to reach out to Mysa’s Customer Experience team. Or, contact a local HVAC professional. 

by LastSale
by LastSale