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Old 12-28-2017, 10:48 AM  
Raindem
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Default Furnace keeps tripping breaker

Hi. I have an Arcoaire electric furnace, model no. MF20N2600A. It runs for about a minute, maybe less, and then trips the breaker. The unit itself has a 50a breaker. Then it runs to a box on the wall with a 40a breaker. At the main fuse panel it is controlled by a 100a breaker. It is the 100a at the main panel that is tripping.

I thought it was odd that the 100a trips but the others don't. So maybe the breaker was bad. I replaced it with a spare 50a that I had lying around and it still trips at the main fuse panel.

Are there any things a DIYer with a multimeter can troubleshoot here, or is it time to call an HVAC repairman?

Thanks

Curt

Edit: Forgot to mention that I've already changed the filter.



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Old 12-28-2017, 10:53 AM  
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So the 40 and 50 amp breakers are not tripping. there must be other breakers. so total draw of all of them is more than 100 but non are overloaded. Try turning other breakers off.


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Old 12-28-2017, 11:28 AM  
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Go with this /\

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Old 12-28-2017, 11:30 AM  
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It is the breaker at the fuse panel that is tripping. When I reset it the furnace will briefly run and trip it again after a minute.
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Old 12-28-2017, 11:45 AM  
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Quote:
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I thought it was odd that the 100a trips but the others don't. So maybe the breaker was bad. I replaced it with a spare 50a that I had lying around and it still trips at the main fuse panel.
At this point no one knows if the 100a is bad or the 50A is bad or good or it is something else.
I'd replace the 100a with a similar unit (but I don't like guessing) or buy/borrow a clampon ammeter for some logical troubleshooting.
What is the nameplate current draw for your unit?

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Old 12-28-2017, 01:53 PM  
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Replacing a 100A with a 50A will definitely trip unless your total load is below 50A. I suspect your 100A breaker is bad, it happens, they can become weak over time. If it just started doing this that would be my educated guess. Your electric furnace is probably the largest load in your house.

Are you running an electric range, water heater, and a dryer at the same time? Those would be your other high load appliances. Do they all go through the 100A main breaker? At my house the HVAC units and electric stove outlet have breakers in the main panel below my electric meter outside. The sub-panel for everything else is in the garage and runs off of a 100A breaker under the meter.
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Old 12-28-2017, 02:24 PM  
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With the Arcoaire off, along with a clock you can use your electric meter as an ammeter and see what current is being drawn.

Your PoCo can supply you with the method, there's some number stamped on the meter that provides the conversion.

100A @ 240V gives 24 kw for an hour (24 kwh) and 0.4 kwh in one minute.
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Old 12-28-2017, 06:42 PM  
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Thanks for the follow up responses. I thought the 50a breaker would be OK temporarily because the other breakers in the circuit were equal or less. I guess I just proved I'm not an electrician.

I think what makes sense at this point is to get an exact replacement for the 100a as someone suggested. And then go from there.

I should point out that this is a small furnace in my workshop, not in the main home. There was nothing else running at the time.
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Old 12-29-2017, 12:36 AM  
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Quote:
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Thanks for the follow up responses. I thought the 50a breaker would be OK temporarily because the other breakers in the circuit were equal or less. I guess I just proved I'm not an electrician.

I think what makes sense at this point is to get an exact replacement for the 100a as someone suggested. And then go from there.

I should point out that this is a small furnace in my workshop, not in the main home. There was nothing else running at the time.
Is there anything else taking power from that 100 amp breaker?
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Old 12-29-2017, 08:26 AM  
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Not that I know of. The fuse panel was mis-labeled and had that breaker as going to a 220V outlet. But I got that sorted out. With the 100a turned off everything else in the shop appears to still be working.


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