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Why is my 70 amp circuit breaker trip periodically when my furnace blower motor kicks off?

brhans
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Kermit
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    What is "kucking" ? – DavidRecallsMonica Nov 21 '22 at 20:07
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    I assume that "kucking" means "kicking." But what exactly does "kicks off" mean? (In the US, that could mean "starts" or it could mean "stops", so...) – aghast Nov 21 '22 at 21:13
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    Also, 70amps seems like a pretty big breaker. Is this the main breaker for the house or panel, or the breaker for an apparently-huge heating system? – aghast Nov 21 '22 at 21:23

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your heat is overloading the breaker. Your heat goes off when the breaker trips, not the other way around.

Tiger Guy
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  • Either that, or you're running close to the edge and the inductive surge when the motor turns off is what pops the breaker... – keshlam Nov 21 '22 at 20:46
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You have a forced-air "furnace" that uses electric resistor heating instead of using gas or a heat pump. The heating element is a huge resistor, sort of like found inside a hair dryer, or any of the portable plug-in heaters.

When your thermostat calls for heat, the "furnace" turns on the air blower and then turns on the heating element.

Your heating element is having a problem. It has some sort of internal short or damage that is causing it to use too much electrical power and make too much heat (in a destructive way that could start a fire).

To prevent that, the circuit breaker is tripping.

It's unlikely it is a faulty circuit breaker. But since they are $20, you might think about having your maintainer start there.

Most likely it is a dirty or faulty heating element. These aren't terribly expensive, but the electric bill to run them is. These things are horribly, horribly expensive to operate - a 70A breaker means a 13,000 watt heating element, costing well over two dollars PER HOUR to operate unless you have a special electric rate (tariff) to cover the usage.

Without such a tariff, the cost of running this thing will be absolutely brutal. You should very seriously, and soon, shop for a Heat Pump option (which is simply an A/C that can work both ways). This is costly up-front (finance it!!) but cuts your electric bill for heating by 70-80% depending on your weather. I must caution you that heat pumps provide very efficient air conditioning, so you will enjoy your house more / enjoy your summer electric bills more.

Harper - Reinstate Monica
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  • The recommendation of an air-source heat pump is good, but the suitability is dependent on the location where the OP is located, which isn't mentioned in their post. Below a certain temperature (which is heat-pump specific to the manufacturer and model), they are no longer efficient, so go to their backup heat source, which is in all likelihood electric, which is, as you noted, quite expensive to run. Another option could be a ground-source heat pump, but that involves a lot more work, underground pipes, etc., but they can work in all regions. Just make sure to get a reputable installer. – Milwrdfan Nov 21 '22 at 21:01
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    @Milwrdfan I once thought that. But it's no longer true. Here's a catch-you-up video on the state of the art. https://www.youtube.com/watch?v=MFEHFsO-XSI&list=RDCMUCy0tKL1T7wFoYcxCe0xjN6Q&index=2 – Harper - Reinstate Monica Nov 21 '22 at 21:53
  • And I would point out, those 100 hours a year in Chicago where Alec says heat pumps "don't work" - they **Actually Do Work** and at well over unity (i.e. more efficient than resistor heat). What they don't do in those 100 hours is beat 2.5 COP or 250% over-unity (as compared to electric heaters). This is a "performance benchmark" Alec establishes earlier in the video which relates to energy security - this was done right after the start of the Ukraine war. – Harper - Reinstate Monica Nov 22 '22 at 21:14