Microwave randomly blows circuit breaker?

[Bulldog13]

Had my garage main breaker panel replaced about 3 months ago…did it mainly because the old panel was I guess a possible fire hazard and I was having trouble getting house insurance here in Florida. So my kitchen microwave is on a 15 amp circuit breaker and randomly trips the breaker? It’s a built in microwave over the range…I called the electrician who installed the new panel and he said it’s probably the microwave going bad? Microwave is maybe 1.5 years old….? I’m not an electrician but could it be a bad breaker or should it be a 30 amp breaker ? Didn’t have this problem before the panel was replaced…Thank for any input..

 

[PCustoms]

Did you use enough ? Marks at the end of every sentence?

Let's start with basic information, what size is your microwave?

 

[Bulldog13]

Did you use enough ? Marks at the end of every sentence?

Let's start with basic information, what size is your microwave?

Sorry about the question marks . I am not sure what size the microwave is….. I just assumed since I didn’t have a issue before the panel was replaced , that might be the issue.

 

[lilredex]

Anytime I had a microwave blow fuses is because of a shorted capacitor in the m'wave.

 

[PCustoms]

Sorry about the question marks . I am not sure what size the microwave is….. I just assumed since I didn’t have a issue before the panel was replaced , that might be the issue.

Over the range or countertop?

You need to know the watts, then you'll know what circuit size you need. Then you need to see what size wire is on that 15A breaker.

 

[Bulldog13]

Over the range …I’m at work so I’ll have to check when I get home .

 

[PCustoms]

Over the range …I’m at work so I’ll have to check when I get home .

Odds are breaker is too small, but if it's 14awg wire that's what he had to use.

 

[BillK]

Is the microwave on its own circuit or are there other things on it ? What model is it ?

When our house was new it only had an exhaust fan and light over the stove and it was on a 15A general circuit with another room and outlets. Some years later I replaced the fan with a built in microwave and used the same circuit. It works fine if nothing else on the circuit is working but if there are a bunch of lights on and my Wife has the iron on it will sometimes trip the breaker. The data tag shows 1480 watts which is 12.3 watts so it is pushing right at the limit. If yours is newer and higher powered it might be more.

 

[sparky 1971]

^^ I agree. The range probably had a vent hood above it originally that was powered from a 15 amp lighting circuit. The previous owners took the hood out and replaced it with the microwave. The microwave tripped the breaker often enough that they stuck a 20 amp breaker in place of the original 15 and "fixed" it. Then you came along and bought the house as is, but when you had the panel changed, the electrician saw a 14 gauge wire and used a 15 amp breaker for it, like he should have.

When the breaker trips, does anything else go out with it? If it truly is connected to a lighting circuit, you can help it by limiting anything else that is running when the microwave is being used, especially if that something else is a space heater. The only real fool proof solution is to install a dedicated 20 amp circuit for the microwave, but if the microwave is going bad, that won't fix anything this go round. I had never seen a microwave go bad until about two years ago, then I ran across three of them causing dedicated 20 amp breakers to trip in about a four month time span, so it is possible that the microwave is shot.

 

[Bulldog13]

I think it’s connected to our guest bedroom and the only thing running is a ceiling fan.

 

[sparky 1971]

I think it’s connected to our guest bedroom and the only thing running is a ceiling fan.

A ceiling fan is going to add a couple of amps to the total load, that might be enough to put it over the edge. Try running a good extension cord from a known 20 amp circuit to the microwave and give it a couple of days. Even better would be to, if you have one, use an amp meter and check the amount of current being used by the microwave and see if it matches up close to the claimed wattage on the name plate. You can buy some ammeters cheap at the box stores if you're so inclined.

 

[Chuckster in NJ]

Every "over the range" microwave, that I have wired, needed a, 'dedicated' 20 amp/120 volt circuit.

Check the amps and you do not want to exceed 80% of the breaker rating.

 

[walta]

Generally, the first thing connected to the black wire in the microwave oven is a 15 Amp fuse that will open the circuit long before a circuit breaker could ever trip for over current.

If a over current fault is in the microwave this fuse had almost certainly been bypassed.

The most likely fault in the microwave is the “monitor circuit” this is several different switches connected to the ovens door when the door is closed power is connected to the timer and high voltage transformer. When the door is opened power is first removed and then a short circuit is put across the HV transformer so it is impossible to make microwaves when the door is open. When the switches get old and gummed up they do not operate as quickly as they should so then power may still be being applied when the shorting switch closes. That should blow the fuse.

Walta

 

[walta]

PS does the circuit breaker that trips have a test button on it? GFCI or AFCI.

Walta

 

[klassenl]

Microwaves do that when they are at the end of their life. If it has a regular 15a cord end then it doesn't need anything other than a 15a circuit

 

[sparky 1971]

If it has a regular 15a cord end then it doesn't need anything other than a 15a circuit

An 1875 watt hair dryer has a 15 amp cord end. Those don't run very long before a 15 amp breaker trips.

 

[The Cobbler]

at the volunteer warehouse, we had a small hot water heater . it was labelled 1440 watts and I think it was a 1 gallon. it was a very small unit, good for hand washing but too small for washing volunteer lunch dishes.
Upgraded to a 6 gal "1500watt " heater . it would blow the dedicated breaker about once per day . after looking for loose connections etc we came to the conclusion it was a weak breaker and had it replaced by our electrician. it hasn't popped for about 8 months .thread here

 

[Bulldog13]

PS does the circuit breaker that trips have a test button on it? GFCI or AFCI.

Walta

No…it’s just a regular 15 amp breaker

 

[RegeSullivan]

Being that the only thing that changed is the new panel I'd pull the cover and have a look. Make sure there are no signs of arcing, wires are tight under their terminals. If all looks good replace the breaker... even new breakers can be bad.

 

[mike93lx]

My money is on the change from a 20a to a 15a breaker

 

[walta]

Does the breaker tend to trip while it is cooking or when or opening or closing the door?

Test the outlet with another load a heater, hair dryer air frier 1500 – 1800 Watts.

Do you own a clamp on Amp meter?

Walta

 

[wyliesdiesels]

make model load rating of microwave is needed before anything else can be determined

 

[PCustoms]

make model load rating of microwave is needed before anything else can be determined

It's been 24hrs and basic info is still not available, this thread isnt going anywhere...

 

[Bulldog13]

It's been 24hrs and basic info is still not available, this thread isnt going anywhere...

GE …it’s says 1600w input , 1000w out

 

[Bulldog13]

Does the breaker tend to trip while it is cooking or when or opening or closing the door?

Test the outlet with another load a heater, hair dryer air frier 1500 – 1800 Watts.

Do you own a clamp on Amp meter?

Walta

I don’t have a amp meter…it trips on start up but only randomly…I have a call out to the electrician but no call back yet

 

[mike93lx]

GE …it’s says 1600w input , 1000w out

The output doesn't matter, but 1600w should run on a 15a circuit

 

[Bulldog13]

The output doesn't matter, but 1600w should run on a 15a circuit

Microwave is 2023 model…so I’m leaning towards a bad breaker…I’m not great with electric so I’m not confident digging into the new breaker panel

 

[mike93lx]

Microwave is 2023 model…so I’m leaning towards a bad breaker…I’m not great with electric so I’m not confident digging into the new breaker panel

If it's something you want to learn, a little youtube and watching the sparky you hire can get you there.

If you kill the main, the only hot things are the lugs, which likely have yellow caps on them and if not, you can add them for under $20 (good thing for the sparky to do while he is there, just pick them up at HD)

 

[sparky 1971]

Microwave is 2023 model…so I’m leaning towards a bad breaker…I’m not great with electric so I’m not confident digging into the new breaker panel

Run a cord from a 20 amp circuit to the microwave and give it a few test runs. I thought I fixed a five year old microwave that would randomly trip on start up by running a new circuit to it since the refrigerator was also on the same circuit. A couple of days later it tripped again and by the time I got there, the random trip was no longer random, the microwave was junk. Another time, I ran a 20 amp circuit for a microwave that hadn't even been purchased yet. Upon installation, it had random tripping so I went back with my meter and everything seemed to check out fine so I blamed the breaker and installed a new one under warranty. A couple of days later I got a call that it had tripped again. I went back and checked and luckily, while I was there with the meter on, got a spike of somewhere around 40 amps on start up. Junk microwave. They took it back, got a replacement and all has been well since.

 

[wyliesdiesels]

while I was there with the meter on, got a spike of somewhere around 40 amps on start up. Junk microwave. They took it back, got a replacement and all has been well since.

wow thats a huge inrush for a microwave

 

[dcg9381]

The output doesn't matter, but 1600w should run on a 15a circuit

120V * 15A * 80% continuous = 1440w.. It's right on the margin. I don't count on breakers beyond 80% for any length of time.

 

[sparky 1971]

wow thats a huge inrush for a microwave

That was just a little 1000 watt P.O.S. that sat in a pantry. Everything is pretty much junk anymore.

 

[mike93lx]

120V * 15A * 80% continuous = 1440w.. It's right on the margin. I don't count on breakers beyond 80% for any length of time.

You run your microwave for 3hrs at a time?

 

[dcg9381]

You run your microwave for 3hrs at a time?

Convection, maybe.

Fair point, but I don't trust manufactures to be quite that precise in terms of timing... Not with an old breaker.

I like the suggestion of throwing a 20A extension on it and see how it does. Or clamp the darn circuit and measure it.

 

[mike93lx]

Convection, maybe.

Fair point, but I don't trust manufactures to be quite that precise in terms of timing... Not with an old breaker.

I like the suggestion of throwing a 20A extension on it and see how it does. Or clamp the darn circuit and measure it.

3 hrs is a hell of a stretch from most microwave use.

I agree, run on a 20a circuit is what I would recommend for someone who doesn't want to open a panel

 

[sparky 1971]

120V * 15A * 80% continuous = 1440w.. It's right on the margin. I don't count on breakers beyond 80% for any length of time.

For it to be a continuous load, it has to run for more than three hours at a time. Post 25 says it trips on start up, a 15 amp breaker would probably go for a few minutes at 20 amps before it heats up enough to trip.

 

[walta]

I don’t have a amp meter…it trips on start up but only randomly…I have a call out to the electrician but no call back yet

Test the curcuit by running a load like heater, hair dryer or air frier 1500 – 1800 Watts on that outlet.

Walta

 

[wyliesdiesels]

120V * 15A * 80% continuous = 1440w.. It's right on the margin. I don't count on breakers beyond 80% for any length of time.

better look at a breaker trip curve chart. breakers are rated to hold 100% of the current rating indefinitely.... and the trip curve is many percentages above 100%

 

[wyliesdiesels]

Convection, maybe.

Fair point, but I don't trust manufactures to be quite that precise in terms of timing... Not with an old breaker.

I like the suggestion of throwing a 20A extension on it and see how it does. Or clamp the darn circuit and measure it.

i doubt a microwave would last running that long. most are rated for intermittent duty