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Why Does My Furnace Have Two Breakers?

Furnaces (and all other electrical devices) use circuit breakers as an essential safety precaution. They can prevent extra electricity from surging through the furnace, protecting your home from any electrical incidents like sparks and outages. But why do some furnaces have two breakers?

Your furnace has two breakers because it’s large and requires a lot of power to operate. Two circuit breakers prevent the furnace from drawing too much current, which could cause serious problems.

The remainder of this article will answer why your furnace uses two breakers and a few related questions, such as whether you need to use both breakers simultaneously. I’ll also delve further into what exactly circuit breakers do and why they matter. 

What’s the Purpose of Two Breakers for a Furnace?

The purpose of two breakers for a furnace is to share the load of electricity needed to power the furnace. Two breakers reduce the chance of failure and improve efficiency.

As mentioned above, a furnace will typically have two breakers if it draws too much energy — more than what a single breaker could handle. For example, imagine a group of students going on a field trip. One bus doesn’t suffice for the entire group, so they split them into two.

This reduces the load that only one bus would have, lowering the chance of an accident. It’s the same case with electricity and breakers! The electricity is the students, and the breakers are the buses.

Should Both Furnace Breakers Be On at All Times?

Let’s say, for example, your furnace works perfectly fine with just one breaker activated. It might seem more energy-efficient to leave one breaker on at all times. However, that is not the case.

The activated breaker handles the controls and the thermostat while the other breaker keeps the heating elements running. It’s not energy-efficient to keep only one breaker on at all times. The only way it can save energy is if you have the furnace cycling on and off.

Ideally, both breakers should stay on at all times.

What Exactly Does a Furnace Circuit Breaker Do?

A furnace circuit breaker prevents excess current from getting to the furnace. Power spikes can damage your furnace, but the circuit breaker trips and blocks all current to prevent that from happening.

Let’s continue with the bus analogy from earlier:

If a bus driver needs to stop along the way to the field trip, it’ll put the students’ trip to a halt. It’s the same case with circuit breakers. Likewise, if a circuit breaker trips, it stops all current flow going to the furnace. The circuit breaker is not just an on/off switch; it’s a special safety device that shuts off automatically when it detects excess energy.

In case you need to identify your furnace’s circuit breaker(s), you can purchase the Klein Tools Circuit Breaker Finder on You plug the outlet tester into an outlet, and the main tool will correctly find the corresponding circuit breaker. As one of Amazon’s bestsellers, you really can’t go wrong with it. 

What Causes a Circuit Breaker to Trip?

A circuit breaker trips if the circuit is overloaded or if there’s a short circuit or ground fault. Whenever the circuit breaker detects abnormal voltage or amperage levels, it’ll block the flow of current to prevent injuries and damages.

Let’s go over each of the three most common causes for a tripped circuit breaker to better understand why your furnace circuit breaker is tripping.

Overloaded Circuit

An overloaded circuit happens when your furnace draws too much current. An overloaded circuit is especially common if you plug in multiple devices at once.

For example, if you plug in a hairdryer while your furnace is running, that can easily overload and trip the circuit breaker.

We can again refer to the bus analogy to understand how this works — There are a few kids in the back of the bus taking up a lot of space. They cause a ruckus, and the bus starts to shake a bit. The bus driver has to pull over to prevent an accident.

It’s the same for circuit breakers; instead of the bus driver pulling over, the circuit breaker trips.

Short Circuit

A short circuit happens when extra electricity is drawn due to a wiring issue inside the furnace. It can also happen if your furnace’s plug isn’t all the way in the outlet. Due to its displacement, it’ll pull more electricity and cause a short circuit. This can even create sparks.

Bus analogy time: 

Let’s say the bus door doesn’t close, but the driver starts driving. One kid almost falls out and hurts himself, so the kid pulls onto a chair to regain balance. Everyone else freaks out and hangs on tight to their seats. To prevent a fatality or injury, the bus driver pulls over.

The same thing happens with your circuit breaker.

Ground Fault

Ground faults happen in areas with a lot of moisture, such as bathrooms. They can also happen if you dry your clothes near your furnace or there’s a puddle of water in your basement.

The moisture can affect the electronics in your furnace, causing an array of problems.

With the bus example again, let’s say a kid spills water. Another kid might end up slipping. The bus driver pulls over to give the kids time to clean up the moisture and get things rolling again.

Once there’s no more moisture, the circuit breaker won’t trip anymore.

Do Furnace Circuit Breakers Really Matter?

Furnace circuit breakers matter. The circuit breaker stops electric current from overloading and damaging your furnace. It also prevents sparks, power outages, fires, and even explosions. Your furnace needs at least one circuit breaker.

Let’s use a bus example yet again: 

A group of small children doesn’t have a bus (breaker). How do they get to their destination? They walk. Without the bus, they’re not limited to the number of people, but they could get robbed, kidnapped, run over, and worse.

It’s the same case with circuit breakers. Without a circuit breaker, electricity is free to roam, which could cause some serious problems. You wouldn’t let your kids roam free like that, so why let the energy do the same?

Final Thoughts

A circuit breaker aims to keep energy from overflowing and causing problems. So, if your furnace has two breakers, that’s because it has more energy or electricity. While circuit breakers may look like tiny little switches, they are much more complex and important.

Be sure to check out the Amazon product if you are interested in checking your circuit breakers. This could help prevent anything from being mislabeled.


  • Jake Alexander

    Jake is a freelance writer from Pennsylvania who enjoys writing about science and sports. When he's not writing for Temperature Master, he can be found watching the NFL or playing basketball with his friends.

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