how to tell if your thermostat is low voltage

How to tell if your thermostat is low voltage? If this is a question you’re always asking, you’re in luck.

Here’s our comprehensive guide to knowing your home’s thermostat voltage!

Most residential homes have a low voltage HVAC system compatible with a similar thermostat. However, some outliers use high or line voltage systems.

The primary concern here is compatibility with smart thermostats readily available in the market.

Let’s go deeper and explore more about thermostat voltages.

The easiest way to tell if your thermostat runs on low voltage would be to open it up and check the panel. If it says 24V or 30V, it’s a low voltage one that you can swap with a Nest or Amazon Smart Thermostat. You also want to check the wiring.

What You Need to Know About Thermostat Voltages

If you want to know are thermostat wires low voltage, there are a few things you will want to know.

As mentioned above, you can easily find thermostats for low voltage systems. You can even use smart ones from Nest, Amazon, and Honeywell.

If you just moved and want to know the thermostat you can get, you want to know the voltage of your system so you can get the right one.

Here are the elements that you are going to be considering before getting that thermostat.

1. Types of HVAC Systems

Different HVACs have their own power requirements. The good news is that most residential systems are low voltage, which helps confirm.

2. Compatibility

Not all thermostats are created equal. Low voltage systems need a thermostat that matches so you can control the temperature. The same is true for high or line voltage systems.

3. Wiring Setup

The wiring setup for these two systems and thermostats are different. You’ll know which one you have with how your wiring looks.

4. Installation Difficulty

If you’re remodeling a home, you want to consider the thermostat type to work around constraints for each system.

These are the things you need to know about thermostat voltages. Let’s now proceed to the different ways that you can tell the type of system you have.

How to Tell if Your Thermostat is Low Voltage

tell if your thermostat is low voltage

There are a few ways to tell the type of HVAC and thermostat you have in your home.

These steps will be incredibly helpful if you’re moving to a new house and want to upgrade your thermostat. You can also use this to determine the type of thermostat to get.

Let’s look at the different ways to tell the type of thermostat that’s going to be compatible with your HVAC system:

Step #1: Know Your HVAC System

Two prevailing HVAC systems are in use today. The most common ones are the low voltage types that are in use in most residential homes.

They’re called low voltage since they are connected to 12V or 24V to power them.

These systems power and control your home’s heating source, which usually burns fuel.

High or line voltage systems, on the other hand, run on 120V or 240V.

Your heating units are usually powered by electricity, and your home’s circuit, thermostats, and heaters are connected.

You’ll know if a system is a high voltage since it uses convection or radiant heat sources.

know hvac system

Low Voltage Types

Here’s how to know if you have a low voltage system:

  1. Boilers, furnaces, and ducted heat pumps are low voltage types.
  2. Only have 1 or 2 thermostats for the entire home.
  3. The heater uses fuels like water, gas, oil, or wood.
  4. There is a central heat source like a furnace or boiler.

Line Voltage or High Voltage Types

Here’s how to know if you have a high or line voltage system:

  1. Electric HVAC systems are high voltage types.
  2. There is a thermostat for every room.
  3. The heat source is powered by electricity.
  4. You have baseboard heaters and floor heating.
Note: A low voltage thermostat is not going to be compatible with a high voltage system.

Step #2: Check the Number of Thermostat Wires

check thermostat wires

The next way to figure out the type of thermostat your HVAC system has is by looking at the number of wires behind the faceplate.

Thermostats connect to your heating and cooling source via wires. A different wire usually controls a different aspect of your thermostat.

The quickest way to determine your thermostat type is by counting the number of wires that connect to it.

Here’s how to know the type of thermostat and HVAC system your home has:

Low Voltage Wiring:

  1. Multicolored wires ranging from red, green, blue, yellow, and others.
  2. Low voltage installations will have wires coming out of the drywall.
  3. Your thermostat has multiple connectors for these wires.
  4. Low voltage thermostats utilize at least 5 to 6 different wires.

Line Voltage or High Voltage Wiring

  1. High voltage systems connect with only two to four wires.
  2. There are only two colors to separate the wires.
  3. Wires go through an electrical box.
Note: Make sure that you turn off power to your HVAC before opening your thermostat’s panels and inspecting the wires.

Step #3: Thickness of Thermostat Wires

check wire thickness

Since the two different thermostat systems handle significantly different loads, there will be a difference in the thickness of the wires.

Since the low voltage systems only carry up to 24V, they will be thinner and more flexible.

High voltage systems carry a much higher load that can reach up to 240V. Their wires are going to be a lot thicker and larger overall. 

Since you’re opening up your thermostat’s panel, you want to check how large or wide the wires are.

Here’s how to differentiate the wires of these two HVAC systems:

  1. Low voltage systems have thinner and more flexible wires.
  2. High voltage systems have thicker and larger wires.

Note: An easy way to know this would be to check if the wires are the same size as your doorbell. If it is, your home is running a low voltage system.

Step #4: Check your System’s Voltage

A sure-fire way to determine your thermostat and system’s voltage is by checking the labels.

If you open your thermostat’s panel, you’ll see the label that will state at which voltage it runs.

There are also instances when the label for your device will not be readily available.

check system voltage

If this is the case, you’ll have to take out your voltage meter to measure how much energy is going through the wires.

Here’s how to check your system’s voltage:

  1. Open your thermostat’s cover.
  2. Check for a power rating label.
  3. If it says 24V, you have a low voltage thermostat.
  4. If it says 120V or 240V, it’s the high voltage type.
  5. You can use a voltage meter to measure.
Pro Tip: Take the necessary precautions when opening your thermostat and dealing with wires.

With these steps, you’ll now be able to determine your thermostat’s voltage requirements accurately.

You can also check the current device that’s connected since if it’s running a programmable or smart thermostat, it’s going to be a low voltage system.

Read Next: How to Fix Amazon Thermostat Schedule Not Working?

Bottom Line

Now that you know how to tell if your thermostat is low voltage, you can confidently figure it out by looking at the wiring.

This will make it easier for you to determine the type and find the right thermostat if you’re planning an upgrade.

However, if you run into any issues, you can always contact an HVAC professional.

They will be able to help out and recommend the best devices you can use to replace an old thermostat.