We are finsihing up a new construction home, and have a Viking Microwave on a 20 amp circuit in the kitchen. This is the only device on the circuit. The microwave cooks fine, but sometimes just closing the door on the microwave trips the breaker! I have moved the oven to another outlet and it doesn't trip other breakers. ANy ideas what might be happeing? I can't imagine closing the door would draw a lot of current! We have used other devices on the same outlet with no problems. thanks! To reply via email remove spamnot
Spudz, sounds like the door is misaligned. When the door is misaligned, the interlocks switches in the holes where the "hooks" on the door go don't activate in the right sequence and the circuits breaker trips or the microwave's internal fuse blows. This, surprisingly, is actually a feature. It is existant to prevent you from operating it with a damaged or misaligned door so you don't expose yourself to potentially harmful levels of microwaves.
Have the door check and, if needed, realigned professionally. Unless you have the skills and tools to test for uWave leaks (which I highly doubt), don't fix it yourself. The repair FAQ website has info on the interlocks and about microwave doors if you DO want to try to fix it.
Spudz, sounds like the door is misaligned. When the door is misaligned,
the interlocks switches in the holes where the "hooks" on the door go don't activate in the right sequence and the circuits breaker trips or the microwave's internal fuse blows. I have seen this happen. This, surprisingly, is actually a feature. It is existant to prevent you from operating it with a damaged
or misaligned door so you don't expose yourself to potentially harmful levels of microwaves.
Have the door check and, if needed, realigned professionally. Unless you have the skills and tools to test for uWave leaks (which I highly doubt), don't fix it yourself. The repair FAQ website has info on the interlocks and about microwave doors if you DO want to try to fix it.
Actually, it does. Because, that situation should never occur unless there is a major problem.
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odd that it is tripping the 20A breaker before it blows the 15A internal fuse though, unless the internal fuse is 20 A. I have also seen bad breakers before, tripping at a lower rating than they are supposed to be, but they have all been old. But if the microwave is not tripping on other outlets, this may be something you want to look into
Sp> We are finsihing up a new construction home, and have a Viking Sp> Microwave on a 20 amp circuit in the kitchen. This is the only device Sp> on the circuit. The microwave cooks fine, but sometimes just closing Sp> the door on the microwave trips the breaker! I have moved the oven to Sp> another outlet and it doesn't trip other breakers. ANy ideas what Sp> might be happeing? I can't imagine closing the door would draw a lot Sp> of current! We have used other devices on the same outlet with no Sp> problems. Sp> thanks!
I saw this very thing last year. Turned out one of the contacts on the electric meter was burning up. Your problem is not likely to be the same but coincidences happen. Perhaps instead the microwave has a door interlock problem. These are designed to trip the breaker, for safety. Is it pretty new?
A*s*i*m*o*v
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It does on the microwaves I've worked on, the secondary interlock switch shorts directly across the line and blows the fuse, of course this is never supposed to happen in actual operation, but is a last resort to prevent exposure to high power microwave energy should the primary interlock stick.
That must be the US way then, in over 15 years of repairing microwave ovens* here in the UK I can't recall seeing one without the resistor.(Sometimes it looks like a slowblow fuse, with what looks like a spring inside) It should still blow the internal fuse first unless the mains breaker is unusually sensitive
A business now sadly gone, people just buy a cheap replacement, it`s cheaper to buy a new oven than to have a fuse replaced
Ron
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A couple of additional possibilities. Note that some circuit breakers will pop before a slo-blo fuse in the same line. Think door switches and read on.
Food material can gather at the operating pip of any of the door micro switches. This can be as small as a very light smear of something sticky. The effect is to slow down the operating speed of one or more switches. This will cause an intermittent door switch timing overlap when either opening or closing the door. The actual switch sequence, the switch affected by food debris, and the particular design of the oven will cause a variety of different scenarios. THIS IS A COMMON FAULT. You may need a 10X jewellers loupe to see some food smears which are fully capable of causing a switch to hang long enough to blow a fuse or trip a breaker.
Another fairly common cause for a switch to hang and disrupt the interlock sequence is much harder to detect and has a greater capacity to have you re-working ovens at your expense. This primarily affects the switch in the sequence that acts as the crowbar, but can also affect even clean primary/secondary switches after some years use. If an oven has had a history of one or more fuses blown without a fault being discovered, the crowbar switch will have had some serious energy fed into its shorted contacts. This ALWAYS leaves a roughened area on the contacts. Roughened contacts do not slide as easily as pristine ones and the slowed-down switch is now likely to blow a fuse intermittently, ***even if the cause for the original fault is found and corrected.***
Best practise, is to ALWAYS, if possible, examine with a loupe the contact area of crowbar door switches. Trust no door switches that have switched full current through them to blow the main fuse. If you have a customer oven or two that blow switches every week or so, suspect food debris and/or roughened contacts.
In my experience, most door switch problems with microwave ovens are caused by (sometimes) tiny amounts of food. I used to buy, and use, 5000 microswitches every 6 weeks or so for this very reason. You cannot effectively clean food debris off switches. Always put new switches into clean housings. To do otherwise is to risk doing the job again ***at your expense***
When the door closes there are multiple interlocks. These are set up to short the ac line and blow the internal fuse if you try to defeat just one interlock. If there were a brief transient short when you close the door it could trip a magnetic breaker before blowing the internal fuse. The fact that it is a problem on one circuit and not another may have to do with the senitivity of the braker which may vary from breaker to breaker. If you are qualified to do work in your breaker box (DO NOT IF YOU AREN"T SURE WHAT YOU ARE DOING!!) you might simply swap the breaker from the circuit that works to the circuit that's sensitive. Or, you could get an electrician to do it.
That's the only way I can see a connection with closing the microwave door unless there is faulting wiring in the outlet that is jarred when you close the door. If that is the case you could possibley get the same effect thumping on the countertop or wall.
Since virtually all microwaves now seem to be run by electronics, I wonder why they don't just program the CPU to detect interlock failures and go into an error condition and refuse to operate, instead of shorting the AC line? That would sound a lot safer to me. Then again, I'm not an expert, so maybe I'm missing something.
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