My Smart Thermostat Keeps Tripping The Breaker

smart thermostat keeps tripping breaker in electric panel

It seems like my smart thermostat is tripping the breaker. Every time I turn on my furnace from the thermostat and the breaker trips. I reset the breaker and turn on the furnace again and the breaker trips, so it’s logical to think that my Nest or any other smart thermostat is tripping the breaker. But it’s not very likely. Let me explain why.

It’s more likely that your thermostat is turning on something in your system that is tripping the breaker. The thermostat is isolated from the power at your electric panel by a small fuse in the furnace. If that fuse were to blow then you would have no read out on your thermostat.

A simple wiring diagram would show that the thermostat is not directly connected to the breaker, but that the components that the thermostat controls are turning on something that is popping the breaker. The simple reason being that the thermostat is controlled by a lower voltage than the other internal parts of a furnace.

Simple example of a furnace wiring diagram

Starting from the upper right, 240 volts is fed to the breaker in your furnace from your main electric panel or from the breaker that keeps tripping when you turn on the thermostat. You may even have more breakers in your main panel and in your furnace, but I’m keeping this simple.

From the breaker a set of wires feeds a transformer (top middle). Notice the two vertical lines in the middle of the transformer. These lines indicate a separation from the high voltage from your electric panel and the low voltage that controls your thermostat. So the idea that a thermostat is tripping a breaker would be very remote.

If somehow a very unlikely situation occurred that resulted in the 230 volt circuit to come in contact with the 24v thermostat circuit then I can see some 24 volt wires at the immediate vicinity of the transformer turning into mass of black melted wire.

Not to say a fire can’t happen but I have never seen anything beyond a component burning up within it’s compartment. Fires need material that will burn and there is mostly metal and some wire insulation within a furnace. They can make a horrible smell.

With that result, your thermostat would have little function if any at all. I have seen many transformers fried. That’s where the rancid burn smell comes from. Sometimes very noticeable throughout the house. But keep in mind here, if the transformer gets smoked then your thermostat will likely not effect a breaker or cause a breaker to trip more than once.

Can My Central Heating Trip A Breaker?

Now we are in a more likely area to find a reason for a breaker to trip. Their are many reasons inside a furnace that can lead to a no heat or no cooling situation and you having to reset a breaker. A few parts within a furnace that can

Chad Peterson

Chad Peterson is a veteran of the HVAC industry since 1977. "I like to explain heating and air conditioning problems in a way the average home owner can understand. "

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