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Old 29-09-2016, 13:59   #16
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Re: Microwave Tripping Breaker

Given the odd breaker size, I figured this was a 220v boat. The inadequate wire size will cause significant resistance at high amperage and voltage drops. The voltage drop can then require higher amperage.

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Old 29-09-2016, 15:11   #17
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Re: Microwave Tripping Breaker

Circuit breakers trip due to heat. Degradation of the metal occurs over time. Motors and heating elements have a ramp up current, which is usually the rated amperage used to heat up the element and start the motor. Once it achieve operating temp and speed, the amperage drawn is reduced. It's possible the ramp up just isnt long enough to trip the breaker. The inductive load of the microwave is continuous.

Lastly, circuit breakers should be selected based upon 75% of intended load, and wire sized to match 125% of the load. So, if you intend to run 20 amps, circuit breaker should be a 25 amp, and wire should be rated to handle 30. Or there abouts. This is because of the heat coefficient. Not at home... In the desert, so the numbers are just examples.

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Old 01-10-2016, 10:40   #18
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Re: Microwave Tripping Breaker

If you do nothing you will have no pop corn !
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Old 01-10-2016, 12:05   #19
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Re: Microwave Tripping Breaker

Originally Posted by cyphert View Post
I've done some further investigating on my previously posted microwave problem. My 1600 watt microwave trips an 18 amp circuit breaker on my boat. It runs for about 10 seconds then the breaker trips. The same circuit will power an 1875 watt hair drier so I figured maybe there was a short in the microwave. I took it home and it worked fine on my houses 15 amp breaker. Any insights? Does a microwave have a "surge" in it's cycle? Is 10 seconds a "reasonable" amount of time before a breaker trips? I'm stumped.

I had a similar situation with a breaker at my house. It turned out that the connection on the back of the breaker was not properly tightened and enough heat was being generated that it was tripping the breaker, not excess current. If your wire size is too small for the load that could have a similar effect. I'd start by taking a look at the breaker connections. Make sure the wire is clean and bright, and that everything is tight. If it still happens, I would then replace the breaker. Lastly, if all else fails I would run in new wire, at least 14 gauge, better 12. If 12 gauge, you could go to a 20 amp breaker.

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