I saw it yes; but that isn't convincing evidence that's what that statement means (or is even correct). It would be quite unusual to have run 12 ga wire for all circuits and then stick a 15A breaker in one slot--I'd not bet much at all that that is the case--and I'd certainly not swap out the breaker w/o verifying is so.
It is possible, granted--I'd just put the odds at being so as low.
The point is to plug whatever else is on that circuit into another if at all possible...has nothing whatever to do with the box itself. Or, replace any old incandescent lights with LED or similar load-reducing efforts. Just don't string a bunch of extension cords all over to move stuff.
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I had an old built-in microwave that I tried to keep working for 10 years. It...
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Clare Snyder
The wiring is sized for 15 amps. Putting in a 20 amp would allow the wiring to be overloaded - not a good idea.
I have another suggestion though. With everything else OFF turn on the microwave, then tuen on everything else. DOes the breaker trip? Might be high surge current when starting the microwave (or one of the other devices - like a high power stereo amp) - and a "high magnetic" breaker MAY solve the problem. I had a problem with my central vac occaisionally tripping the breaker. It was on a "dedicated" circuit (I DID plug my Wifi Router and Cable Modem in to it). I switched the breaker out to a tandem (120/240) breaker which is a "high magnetic" design and it has not tripped since. The tandem breaker was a LOT easier to find (and cheaper)than a single "high magnetic" breaker for my QO loadcenter.
from Schnieder website:
Standard QO115 and QO120 circuit breakers are manufactured to have a magnetic trip point at approximately 8x to 10x the breaker rating. There are some applications, however, in which a load has an inrush current high enough to cause these standard circuit breakers to trip. Examples of these loads include area lighting for athletic fields, parking lots, or outdoor signs. To allow the high inrush current without tripping the circuit breaker, a high magnetic breaker should be used. These high magnetic breakers breakers have a magnetic trip point set much higher than the standard circuit breakers. They can be identified by the HM suffix on the catalog number (QO115HM). Current production HM breakers are also identified with a "High Magnetic" label on the side of the breaker (see photo). NOTE: The above explanation comparing the standard breaker to the high magnetic breaker applies to 1-pole, 15A and 20A, QO, QOB, QOU, HOM and CHOM breakers only. Other ampere 1p breakers, and all 2-pole and 3-pole versions are already high magnetic as standard. (Breakers with suffix GFI, AFI, CAFI, or DF are not available as high magnetic).
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Clare Snyder
Try replacing with an HM breaker - high magnetic trip. Protects at 15 amps for steady load but allows a MUCH higher surge current. Normal 15 amp breaker will hold about 125 amps of surge. HM will hold over 300.
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Clare Snyder
Where is this flat located? What model load center is installed? WHat circuit breaker is currently installed??????
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DManzaluni
Sorry, not sure of these technical details but I sure feel more comfortable trusting your statement that it is unusual to put a 15 amp cb on wiring sized for 20 amps, rather than my super's supposition that 'all wiring behind the box is the same'!
By the way, I should mention that when the cb trips, it does so after a minute or so of the microwave being turned on. It doesnt happen immediately.
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dpb
It's certainly far more conservative and known to be in Code as 14 ga is smallest for general circuits. If you have access to the box, it's simple enough to find out...in a condo w/ owner association, though, it's quite likely that's a "not allowed" operation by the householder.
You can, of course, pull the cover off the outlet and see what runs to the outlet. It would be unusual for it to be different from one end to another, but not impossible and the breaker has to be sized for the smallest wire size on the circuit.
That's indicating the steady load is too much or the previous possibility mentioned that the breaker is thermally sensitive.
Is there anything else on that circuit at the time?
The A/C compressor breaker here developed such a symptom a few years ago...it's not impossible that a new 15A replacement won't trip.
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Clare Snyder
Then we KNOW it is overload, not surge. What goes out with the microwave when the breaker trips? List EVERYTHING on the circuit - and with it ALL turned off/unplugged does it still trip?
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DManzaluni
Yes, I am pretty sure now that it is overload and that some way will have to be found of getting a line from the microwave to a spare slot for a new cb.
When the microwave isn't on, the breaker never trips; and with the old GE Profile, I could prevent tripping by turning down to half power.
Curious that the super didn't seem to know that (I'm sure that) everyone in the building needs to install a separate breaker whenever anyone puts a modern microwave in but I'll bet this says more about his competence than it does abut the wiring!
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trader_4
There are certainly plenty of microwaves that can be run on
15A circuits, even with some other small loads. I'd get a new $100 oven instead of paying $2000 to run a new circuit. You say that all the other circuits are 20A, is there a 20A receptacle nearby that you can use with a reasonable extension cord? I assume you've verified that this circuit still trips with just the microwave? What is the rating on this MW? Have you tried running it at 80% power? What happens then? You asked how to check the breaker and I suggested putting some known resistance loads on the circuit, increasing towards 15a and see when it trips.
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