Why does new 1700 watt microwave keep burning out my 20amp dedicated breaker?

[Toddvandy]

20amp outlet, 20amp breaker, 14 gauge wire. I suspect I need a larger wire but that’sa lot of trouble to go through without being sure.

 

[westward10]

What do you mean by burning out.

 

[telectrix]

is the microwave on 120V or 240V?

 

[pc1966]

Can you post a photo of the damage?

 

[Toddvandy]

What do you mean by burning out.

Broken, kaput, no longer works. No visible damage, just a broken breaker. New breaker works for a bit then also stops working. Doesn’t trip, just breaks.

 

[Toddvandy]

Can you post a photo of the damage?

Nothing visible. But I didn’t open up the breaker to look inside.

 

[Toddvandy]

is the microwave on 120V or 240V?

120. Psuedo professional electrician told me I need to run a 10 gauge wire to the box. But I assume 12 would do it. What else could it be? The outlet stops working even though the breaker is still switched on. Sensor pen tells me there’s still some electricity flowing but not enough for a light.

 

[westward10]

How old is your panel is it the Stab-Lok style, can you show a pic.

 

[Lucien Nunes]

Breakers don't usually stop working due to overload because that's what they are there to protect against. They should trip before being damaged. Therefore I agree with @westward10 that the first breaker might actually still be OK but was not making good contact with the busbar in the panel. Replacing the breaker re-made the contact for a while, and now it has gone open-circuit again, or some similar explanation other than the breaker itself. Or, the breakers are faulty (are they from the same source / batch?)

In this scenario the non-contact sensor is not the best tool for tracing as it may not clearly show the difference between a genuinely hot wire and one that is floating. However, if with the breaker and oven both switched on and the outlet apparently dead, just check whether it lights on both the hot and neutral of the circuit, because if it does that clearly points to a bad neutral connection at the panel which you might not have checked yet.

I would check the breakers away from the panel with a continuity tester as this will prove quickly whether there is a circuit through either or both of them, without relying on the contact through the panel busbar.

The #10 wiring thing seems to be a red herring. If the circuit is very long then #10 might be needed for optimum voltage at the outlet, but it shouldn't in any way affect the breaker. This is new, copper wiring yes? Not a re-used old aluminum circuit?

 

[Toddvandy]

Breakers don't usually stop working due to overload because that's what they are there to protect against. They should trip before being damaged. Therefore I agree with @westward10 that the first breaker might actually still be OK but was not making good contact with the busbar in the panel. Replacing the breaker re-made the contact for a while, and now it has gone open-circuit again, or some similar explanation other than the breaker itself. Or, the breakers are faulty (are they from the same source / batch?)

In this scenario the non-contact sensor is not the best tool for tracing as it may not clearly show the difference between a genuinely hot wire and one that is floating. However, if with the breaker and oven both switched on and the outlet apparently dead, just check whether it lights on both the hot and neutral of the circuit, because if it does that clearly points to a bad neutral connection at the panel which you might not have checked yet.

I would check the breakers away from the panel with a continuity tester as this will prove quickly whether there is a circuit through either or both of them, without relying on the contact through the panel busbar.

The #10 wiring thing seems to be a red herring. If the circuit is very long then #10 might be needed for optimum voltage at the outlet, but it shouldn't in any way affect the breaker. This is new, copper wiring yes? Not a re-used old aluminum circuit?

First, thank you for your time everyone, I appreciate it. Copper wire, newer box, old 1200w microwave was connected to a15amp outlet and same 20 amp breaker for several years. After installing new microwave it stops drawing power after a few cooks. I replaced the outlet to a 20 amp and still nothing. I replaced the breaker and it worked again. Until the same thing happened a couple days later. Breaker and everything is solidly connected. As an ametuer I don’t have the testing equip or knowledge about breaker to see if it still works. There is one other thing I did and that was run another 5 foot wire off the outlet for the gas range below to plug into. (Just for clock, spark and timer) However, nothing was plugged into it or drawing extra power both times it went out. Should I try a gfi outlet? I don’t know how to get it working again other than installing another (3rd)new breaker.

 

[westward10]

Installing another breaker is not the way forward. Does the breaker screw to the busbars or does it just clip onto them.

 

[Lucien Nunes]

You could lose a lot of time on trial-and-error swapping out of parts. It really does make sense to test, or get someone else to test, where the problem is. If for example it is the contact between the breaker and the panel busbar that is intermittent, swapping it will probably make it work again briefly, but so would putting the original one back. WIth proper test equipment it should be possible to nail this in a few minutes.

 

[Toddvandy]

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How old is your panel is it the Stab-Lok style, can you show a pic.

Box seems newer. No brand name that I can see. Measured wire again and it’s actually a 12. Breaker connection is solid. Worked fine with 1200 microwave. Do you think it could be the microwave? Should I install a gfi outlet?

Installing another breaker is not the way forward. Does the breaker screw to the busbars or does it just clip onto them.

clips on. Put the old one back on, still doesn’t work, put a new one in, works. But I’m not going to run the microwave yet.

 

[Toddvandy]

You could lose a lot of time on trial-and-error swapping out of parts. It really does make sense to test, or get someone else to test, where the problem is. If for example it is the contact between the breaker and the panel busbar that is intermittent, swapping it will probably make it work again briefly, but so would putting the original one back. WIth proper test equipment it should be possible to nail this in a few minutes.

Can you tell me exactly the testing equipment I need and what I should test? Am I just testing the breaker? 2 breakers have stopped working. They don’t work when I put them back in. A 3rd new breaker works again but I don’t want to run the microwave until I can figure this out.

 

[westward10]

That is Square D QO. Have you tried the breaker in a different position or temporarily connect to another 20A breaker, don't move it just connect your wire to another breaker.