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We have a double Thermador oven in our house. We've owned the house for around two years, and the oven has worked fine up until the last few weeks. Now, using either of the ovens trips the circuit breaker after around 5 minutes.

The circuit breaker is a 50 amp breaker labeled "Internal Common Trip". You can see it circled here in this unfortunately grainy picture. Note, the one to its right and the pair below are also labeled "Internal Common Trip". No others in the panel are labeled this way:

full view

And also, the bottom half of it here:

bottom half view

I can add more images when I get home from work.

Anyway, I'm trying to determine what's more likely the cause of the tripping. My wife says she smells a faint burning smell from the panel when it trips. I have a home warranty which will cover (with a $100 copay) repair, but I have to pay a separate copay for the appliance repair shop and then another if it turns out to need an electrician (assuming the appliance shop can't do the electrical work itself).

What would be more likely in this case? A bad breaker or a bad oven? Are there any steps I can take to narrow down the cause?

Thanks!

  • Are you able to remove the oven, so that you can inspect the wiring? Do you feel comfortable troubleshooting electrical circuits? – Tester101 May 22 '15 at 14:34
  • A common failure for ovens, is that the connections to the electrical system work loose. The loose connection causes heating, which leads to a failure in the wiring. Leave the breaker off until you get it fixed. If you can visually inspect the wiring at the oven, the failure could be fairly obvious. – Tester101 May 22 '15 at 14:40
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It doesn't sound like a short. It happens after five minutes... each time. To me it also sounds like loose wiring or a bad breaker. I would turn the circuit off and than I would visually inspect the back of the receptacle first. Are the screws tight? Any burnt looking wires anywhere in the box? Than if that is good I would switch that breaker out for a breaker that works. If it holds, you know your breaker needs to be replaced.

You must have confidence in knowing you know how to turn off circuits to do this. If you are uncomfortable, just call an electrician. I am sure it won't take them that long to figure it out. You could even have a breaker at home for them ready (and return it to a store- if they will let you- if he does not need it.)

  • I replaced the breaker and everything works fine. Thanks! – jbwiv Nov 6 '15 at 14:43
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My suspicion is that it is a faulty igniter (glow coil) in the oven.

I had the same problem with my NXR oven. At first the circuit breaker would trip somewhat unpredictably while the oven was on. I had a service technologist come out who could find nothing wrong with the oven. After a few more weeks the circuit breaker started tripping fairly consistently after approximately 1-2 minutes of turning the oven on. Each time before the breaker tripped, I could see that the igniter of the main oven was heating up normally as it got hot and started to glow orange. The igniter is a glow coil that turns on as soon as you turn the oven on and that stays on as long as the oven is on.

To pinpoint the problem, I tested several variations. Turned the broiler on as this uses a separate igniter - This did not trip the breaker. Turned the oven light and fan on without turning the oven on - This also did not trip the breaker. Turned on other appliances that are on the same breaker circuit - This also did not trip the breaker. Based on all of the above, I deducted that the problem was most likely caused by the igniter of the oven.

I bought this new igniter on amazon for $16 to replace the old one:

(http://www.amazon.com/gp/product/B001DPQN70?psc=1&redirect=true&ref_=oh_aui_detailpage_o02_s00)

There are several sites with instructions on how to replace an igniter in a gas oven. I used this one:

http://ths.gardenweb.com/discussions/2288437/if-susan-fixed-her-nxr-oven-ignitor-u-can-2

Since I replaced the igniter, the oven has worked great and the circuit breaker hasn't trip anymore.

I think, although I was never able to confirm this, that after the igniter got hot (takes a minute or so), it somehow caused a short circuit. I checked the resistance of the faulty igniter after removing it and it was normal (same resistance as new igniter). Not surprising as I was checking the resistance when the igniter was cold and the circuits never tripped right away after turning the oven on when the igniter was still cold.

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There is obviously something wrong, and I highly doubt it is the breaker. You can view the wiring in the panel by turning off the main breaker and unscrewing the cover plate. You will see something like this:

breaker box

As you can see, there is not much opportunity for a short, however, if the wires are touching somehow and burnt, then it could be a short. You could "fix" this by separating the shorted wires, but this would leave a dangerous condition. Normally the entire run would have to be replaced--by an electrician.

In any case, it is unlikely it is in the box, and more likely to be farther upstream in the circuit. Debugging oven circuits is a job for an electrician.

  • 1
    Thanks! So you recommend going with an electrician before calling appliance repair? – jbwiv May 22 '15 at 22:11
  • Yes, electrician first. Don't forget the form 27B/6. – Tyler Durden May 22 '15 at 22:14
  • So, on a whim, I went to home depot and bought another 50 amp internal common trip circuit. I replaced the existing circuit, and so far, we've been able to use the oven a number of times and it's yet to trip. Does this indicate that it was indeed the breaker, or could the new breaker be hiding a potentially more dangerous issue? – jbwiv Jun 9 '15 at 14:55
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    @jbwiv If the breaker is the same rating as the old one and it is not tripping, then it could be a defective breaker; in my experience it is rare for breakers to fail, but who knows, maybe newer breakers are being constructed which are lower quality than the old ones. – Tyler Durden Jun 9 '15 at 14:58
  • Ok, thanks. One final question...regarding the two wires going into the breaker, i'm almost certain I got them in the same order as they were before, but there's no marking to distinguish between the two. Does it matter which wire goes in which "port", and if so, wouldn't I know I was wrong at this point since it's been working for three days? Oh, and one more final question...the old breaker had 50 written on it once on the handle. The new one has 50 written on both sides of the handle, so twice. However, I assume they're still both 50 amp breakers? – jbwiv Jun 9 '15 at 15:01

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