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What Gauge Is Thermostat Wire? (Explained)

Are you interested in increasing the heating and cooling system’s efficiency? So, you’ll need to be familiar with the various kinds of heating and cooling wires. Here’s a guide to help you choose the right thermostat gauge.

What gauge is thermostat wire?

Thermostat wire should adhere to the national electrical code. The thermostat wire should be 18 gauge. Additionally, the thermostat wire should have a minimum of five conductors. Additionally, certain thermostat components utilize an 18/10 AWG high-temperature wire. 

Insulated thermostat wire is constructed with a special type of insulation that prevents heat loss. 24 gauge insulated wire is the most frequently used for HVAC thermostat wiring. 

Because this type of wire can withstand higher temperatures than other types of wiring, it is frequently used for outdoor heaters and air conditioners.

24v thermostat wire:

The gauge of wire for a 24v thermostat should be 18/5. But it’s also common for the wire to be 18/4. The wire should be the same size for nipples and tucks. This way, it can carry 1 AWG wire well enough. 

This ensures that the voltage is spread out more evenly and that the thermostat can handle the higher voltage.

Can I use 14, 16, 20, 22, or 24 gauge wire for a thermostat?

The thicker the wire, the more power it will take to heat a thermostat. You can use the 14, 16, 20, 22, and 24 gauge wire for a thermostat, but You should not use 22 and 24 gauge wire because the wires are too thin and can break. Here are more details about these gauges.

14 gauge wire:

14 gauge wire is the best choice for a thermostat because it is a common gauge used in-home wiring and is easy to find. Because this type of wire is so thin, it will take more power to heat the thermostat. Putting 14 gauge wire through a wall or ceiling can be too thin and break.

16 gauge wire:

It can work with a thermostat, but not very well. It’s thicker than 14 gauge and could break if put through a wall or ceiling, so it’s not very good. 16 gauge wire, on the other hand, usually needs more power to heat the thermostat.

20 gauge wire:

If you want to use 20 gauge wire in a thermostat, that’s fine. And it’s also used in commercial wiring, which is why it’s so common. When it comes to thickness, though, 20 gauge wire may not be able to fit through some walls or ceilings. It is thicker than 16 and 14 gauge wire.

22 gauge wire:

Using 22 gauge wire in your thermostats isn’t recommended because it’s so thin that it’s easy to break. It’s also not strong enough to withstand the high temperatures found in thermostats. 22 gauge wire is not strong enough. 

To use in thermostats, you should use 23 gauge wire because it is thicker and more resistant, making it last longer.

24 gauge wire:

A 24 gauge wire isn’t usually used in thermostats because it’s a very thin metal wire, and it’s easy for that wire to break. As long as the wire is less than 2 inches in diameter, the wires will not fit through walls or ceilings with most thermostats. 

If your wiring requires a thicker gauge to get you through some interior ceilings, try 24 AWG or 26 AWG wire instead of the standard 24 gauge.

Thermostat wire gauge size:

ThermostatWire gauge size
Furnace thermostat18/5
AC thermostat18/8
Nest thermostat18-22
Honeywell thermostat18/4
Ecobee thermostat18/7
Millivolt thermostat18/5

What are wire gauges?

You can use wire gauges to measure the size, thickness, and other things that make up the wire. They’re also used in the construction and metalworking industries and by people who make things and AWG (American Wire Gauge), ISO, and DIN.

AWG is the most common wire gauge. People use AWG to measure things like how big, thick, and other things wire. There are many different types of wire, like 28 gauge, 22 gauge, and 18 gauge. It is the most common type of wire to use, called 16 gauge.

How do I know what gauge my wire is?

Wire gauges are used to figure out how big a wire is. People use them to measure wires. They come in various sizes and are usually marked with the diameter of the wire they are meant to measure. Here’s how you can figure out the gauge of your wire.

Measure the thickness:

The easiest way to figure out the wire gauge is to measure how thick it is. Make sure to hold the wire up to a light and look for the letters or symbols on both sides of the wire. These markings show what kind of wire it is, its size, and who made it.

Inspect stranded vs solid core wires:

If you don’t have a way to look at the stamps on your wire, you can look at it under a microscope. Stranded wire is made up of many small metal wires that connect. This is not the same as solid core wire, which is just one piece of metal. 

If you don’t know what gauge your wire is, it’s usually safe to use the same one.

Check the wire’s size:

ISO wire gauges measure the diameter, thickness, and other properties of wire, like how thick it is. Another way to figure out the wire gauge is to look at how big it is. Having a small number makes the wire thicker, so it’s thicker. 

Because 16 gauge has a low number (16), and 26 gauge has a high number (26). (26).  

What kind of wire is used for thermostats?

C wire is usually used to connect thermostats to the power source. If you want to use a thermostat, you can use a few different types of wire, like this: Wire with rubber insulation is the most common. It can be bent to fit any shape or size. 

In addition, it can withstand the weather and isn’t going to rust.

Another type of wire is metal-coated wire, which is more durable and can handle higher temperatures. Besides not being weather-proof, it is also not very flexible. This is the last kind of wire: plastic-coated wire, which isn’t used as often and isn’t as durable as metal-coated wire.

What is the difference between 2 wire and 4 wire thermostats?

Two-wire thermostats are commonly used in residential settings. They have a single wire that connects the thermostat to the heating or cooling unit. 4 wire thermostats are commonly used in commercial applications. 

They have four wires that connect the thermostat to the heating or cooling unit.

The fourth wire is labeled “power” and controls the thermostat’s power consumption. Thermostats with four wires are more accurate and require less maintenance, but they are more expensive. 

You can also use this wire to connect a security system to the thermostat for remote activation. 2 wire thermostats are less expensive but less accurate than four-wire thermostats.

What wires are in my thermostat?

Depending on the type of thermostat you have, the wires in your thermostat may differ. There are two wire thermostats and four-wire thermostats that are commonly used. Here’s how to tell if your thermostat has wires.

Look for label:

Examine the thermostat’s label. This will tell you what kind of wire it is and which poles it is intended for.

Inspect build quality:

If you don’t have a label, look at your thermostat’s construction quality. Two black wires connected near the heat or cooling unit are typical on two-wire thermostats. Four black wires connected near the heat or cooling unit are typical on four-wire thermostats.

Use a multimeter:

If you don’t have a label or are unable to inspect the build quality of your thermostat, you can use a multimeter to determine which wires are connected to what. Determine which wire is hot (or cold), then measure the resistance between that wire and another healthy ground. 

If there is no voltage on any wires, they are almost certainly all connected.

Use a diagram:

If you still can’t figure out which wires are connected, a wiring diagram can help. A wiring diagram will show the colors of the black and white wires and where they are connected.

Final thoughts

In summary, the thermostat wire is typically 18/5 or 18/4 gauge. Here, 18 denotes the gauge number and 4 and 5 denote the conductor numbers. The thermostat can be fastened with C type wire. The gauge can be determined by measuring the wire’s thickness.