Recently, I was called for a similar problem. The microwave outlet was worn. The plug was loose in the outlet. As soon as I replaced it, all was well.

Another possibility: What else is on that circuit? Shut the microwave breaker. Using a tester, see what else doesn't have power. It may just be a coincidence what happened with the extension cord.

 

Microwave got its own breaker. Nothing else shares that breaker. I have replaced the outlet already and that made it work for a week. Then started tripping. After installing the extension cord in the middle, it never tripped (used it for over a week). Removing the extension cord caused it to trip again.

 

How many amps is the breaker, same question for the outlet? What gauge wire is connected to the breaker? How old is the microwave? Is there any chance that something started to block the vent? Was any other work recently done in the house?

 

Both breaker and outlet are 20 ams. Nothing has changed in the last 4 1/2 years. Its the same microwave which worked fine but then recently started tripping. Without changing anything and just installing an extension cord in the middle makes it work fine. Removing the extension cord and plugging it directly in the wall causes to trip. Tripping happens randomly and doesn't always happen. But it does happen at least once or twice a day while using the microwave. Ven't isn't blocked (can feel the air outside where the vent is when microwave is running).

 

The quick and cheap it change the outlet and take it out of the discussion.

 

Already have changed the outlet. Same issue

 

Well, if the OP is 192% sure his new receptacle does not have a loose connection, is polarized correctly, no nicked conductors that are acing to ground once warmed up...then

I think he has a magnetron going bad. The longer extension cord just allows the sudden inrush current needed when the mag fires ....to settle down, and the breaker never picks up the overcurrent. Plug it back in to the wall outlet, and then the shorter current carrying length of the house wiring, and the breaker picks up the overcurrent sooner and trips.

This is my story and I am sticking to it, until someone comes along with one better. :smile::smile:

 

In other words, try/buy another microwave?

 

Why, sure. He could borrow someone's working microwave of the same output wattage size and see if it trips the breaker, while just plugged in the wall while being used. If it does trip the breaker, he has circuit/breaker wiring issues.

I would say he could buy one and refund it if not needed, but that's not nice, so no one should do what I just mentioned.

 

I would try a different breaker. If there is a 20 amp breaker close to the one for microwave, swap the wires. I have seen breakers get weak and trip below their rating.


Moved to electrical forum.

 

Does it trip the breaker when opening and closing the door?

They have interlock switches - 3, two normal ones and a monitor switch. they're designed so that if one switch fails, the monitor switch shunts power directly to neutral intentionally to blow the fuse in the microwave - but in some cases the breaker may trip instead.

 

Post # 5.......

 

Is this an AFCI breaker?

 

Please identify the breakers used on both circuits ?
Are they just standard over current breakers ?
Or are they gfci
Or are they afci

This is important !

:glasses:

 

Please identify the breakers used on both circuits ?
Are they just standard over current breakers ?
Or are they gfci
Or are they afci

This is important !

Normal breakers. Same that were used for the last 4 1/2 yrs. Nothing has changed except the tripping part.

Yo make it clear, sometimes it runs for 10 yo 15 mins then trips and sometimes it trips within 5 to 10 secs. No pattern I've been able to find so far.

 

First thing I would do is hang an amp-meter on that breaker and do some checking before anything else.


Micro weak, loose connection, breaker faulty.

 

I would change the breaker, it sounds like it's a weak breaker and when it heats up, it trips. Just change it with the same amp breaker and make sure the wires going into the breaker are tight.

Sent from my SM-N920P using Tapatalk

 

measure the current before assuming the breaker is bad.

 

"Mentioned already"

 

I'll hazard a guess.
I suspect the cord for the microwave has developed a slight short over the past 4 1/2 years, an arc fault. When you plugged it into the extension cord, you moved the cord and in turn positioned the conductors in the cord to remove the short.