Where is the voltage on a thermostat?

Asked By: Bashir Guerrero | Last Updated: 24th March, 2020
Category: home and garden smart home
4.4/5 (113 Views . 9 Votes)
The most common type of voltage from a central heating and/or cooling system is 24 volts (24Vac). The old thermostat may say somewhere on the thermostat that it is for 24 volt (24Vac) or maximum 30 volts (30Vac). If you see 120 Vac or 240 Vac on the thermostat, a low voltage thermostat will NOT work with your system.

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Likewise, people ask, what voltage does a thermostat use?

24 volts

Beside above, how do I know if my thermostat is working properly? 4 signs your thermostat is bad

  1. Sign #1: Your thermostat has no power or is unresponsive.
  2. Sign #2: Your heater or A/C won't turn ON.
  3. Sign #3: Your A/C or heater runs constantly and won't turn OFF.
  4. Sign #4: Room temperature and setting don't match.
  5. Step #1: Make sure thermostat is on the right setting.

Thereof, how do you test 24 volts?

Using a multimeter to test the flow of electricity throughout the electrical system is the simplest way to find any problems. Turn on your multimeter and set it to read volts. Set the range on the meter to between 20 and 30 volts so you can find the problem in your 24-volt electrical system.

How do you test if a thermostat is working?

Here's how to test your thermostat to see if it works:

  1. With the power to the furnace off, remove the thermostat or thermostat cover to expose the wires.
  2. Unscrew and remove the wires from their terminals.
  3. Twist the bare ends of the two wires together.
  4. Turn the power to the furnace back on.

37 Related Question Answers Found

Are thermostats AC or DC?

Heating or cooling room thermostat voltage levels & power sources: where does a wall thermostat get its electrical power & what voltage level is usually required. While most thermostats use a 24V DC circuit, some use different voltage levels and / or 120V AC is used by line voltage thermostats.

Can I use a line voltage thermostat for low voltage?

Line voltage thermostats are typically used for radiant, convection or resistance heaters that are powered by electricity. Line-voltage thermostats typically have two or four wires coming out of the back of them, which are much larger than the wires you'll see on low-voltage thermostats.

What happens if thermostat wires touch?

hat said, the 24 volts that are fed to the thermostat are from a special thermostat relay, and closing the circuit between the wires, is what the thermostat does, when it calls for heat. So no, you did not hurt anything by touching the wires together.

Why is my thermostat not getting power?

The power is out or a circuit breaker has tripped
The power loss could also be the result of a tripped circuit breaker that powers the air conditioner or heater. Many thermostats run on low voltage sent from the transformer on the HVAC system; if the transformer loses power, so will the thermostat.

How do you test a thermostat valve?


Start your car's engine and allow it to idle. Look through the radiator filler neck to see if the coolant flows. At this time, it should not be flowing as your car has not reached the operating temperature to cause the thermostat to open. If you find the coolant is flowing, it means the thermostat valve is open.

How do you identify thermostat wires?

Here are common uses for wire colors:
  1. Blue or Black – C – Common wire, may be unused by your existing thermostat.
  2. Red – R – 24VAC power from the furnace's transformer.
  3. Red – Rc – 24VAC (dedicated to heat call)
  4. Red – Rc – 24VAC (dedicated to cooling call)
  5. Green – G – Fan.
  6. White – W – Heat.
  7. Yellow – Y – Air conditioner.

How many volts does a Nest thermostat need?

higher than 3.6V when it's charging normally. the battery charge and delay shutting down completely. 3.7V is required to install a software update. 3.6V is required for the display to turn on when you approach.

How do I know if C wire is live?

It is easy to see if you already have a c-wire connected to your system. Simply remove your current thermostat face from its baseplate and look for the terminal labeled with the letter “c.” If this terminal has a wire attached to it, you have an active “c-wire.”

What does 24vac mean?

24VAC input and output uninterruptible power supply.

How do you use a voltage tester?


How to Use Voltage Testers
  1. Determine whether the electricity is on or off by using a two-prong voltage tester.
  2. Place the black lead wire on the other screw.
  3. Test a receptacle using a plug tester.
  4. Use the right size of voltage tester.
  5. Test using a non-touch voltage tester.

How do line voltage thermostats work?

But are you aware of a thermostat called a line thermostat? It works in much the same way as the others only it opens and closes the electrical circuit that powers the heater itself. Unlike the low voltage stats that break the contactor power, this is basically a switch controlled by the temperature.

How do you convert a low voltage thermostat to High Voltage?

You replace the line voltage thermostat with the switching relay, then add low voltage wire from a transformer to power the Nest or other low-voltage thermostat. Wires from the low voltage thermostat simply run to and turn on or off the switching relay.

Can you use a 240v thermostat on 120v?

when you're up over 2kw, 240V is just the smart way to go. You can use mechanical 240V thermostats with 120V just by wiring both poles in series. That won't work with electronic 'stats, as they need a way to power themselves and they are "geared" to poach power off the 240V.

Is thermostat low voltage?

What is a Low Voltage Thermostat? A low voltage thermostat is a direct wired heater and air conditioning control that is found in most homes and operate under 30V. These types of thermostats are popular because they use less power than a line voltage thermostat, averaging around 24 Volts.

What is the purpose of the thermostat?


Any liquid-cooled car engine has a small device called the thermostat that sits between the engine and the radiator. Its job is to block the flow of coolant to the radiator until the engine has warmed up. When the engine is cold, no coolant flows through the engine.

How do thermostat sensors work?

When you install a smart thermostat and set the temperature, the thermostat is only sensing the area around it. Room sensors allow you to see the temperature in every room you put them in, meaning you have a better idea of what the temperature is over your whole house.

What are the different types of thermostats?

There are four basic types of modern thermostats: Non-programmable, programmable, Wi-Fi and smart. The further you get down the list of the thermostats discussed below, the more expensive they become. However, energy efficiency increases with each thermostat.