One circuit often blows

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Lately, one circuit on my box blows. It covers the microwave and regular oven. I could understand it blowing when another heat-using appliance, like toaster oven or toaster runs at same time as microwave. But now it's blowing all on its own.
Last time, today, only the micro was being used, to "reduce" a glass dish of chicken drippings.
Can one circuit go bad all on its own? If so, why? And what should I do about it.
Any info appreciated.
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Higgs Boson wrote:

Maybe the breaker is loose or going bad.
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20 amp breaker for my living room was tripping so I swapped the wires to my bedroom. Problem stayed with the breaker indicating the breaker was bad.
Jimmie
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Higgs Boson wrote:

Breakers go bad. Buy new breaker.
Jon
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As others have said, probably a bad breaker.
Quick test: Plug the microwave into another circuit and use it as normal.
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What is the "regular oven" you speak of? Like a toaster oven but larger? It may have been marginal all along. What is the rating of the two appliances? If the microwave motor is starting to go, it may be pulling more amps that it normally does.
Also. what is the actual voltage coming in? In the summer with heavy loads, the power company sometimes reduces the voltage a bit and that increases the amps. If you live in an area of high tempertures that may be going on some days as the AC load goes way up.
120 volts with a 1500 watt appliance = 12.5A reduce to 110 volts and you get 13.6A Maximum safe load on a 20A breaker is 16A
Others are saying a bad breaker, but while it may be that, I'm guessing overload. Personally, I'd not run a MW and oven together for just that reason.
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Ed Pawlowski wrote:

Whaaaaat?
I seriously doubt that you are correct about that. I say the current at 110 volts would be closer to 11.5 amps. It's quite unlikely that an appliance would be sophisticated enough to continue to consume the same number of watts when the voltage is lowered.
Jeff
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I didn't make the laws of physics, but I usually follow them. Amps = volts watts. If one changes, another will. Are you saying the rated watts of the heating element will change?
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wrote:

stay the same, and if the voltage drops, the power consumed will also drop. The only place that doesn't happen is with induction motors where the back EMF drops, making them draw more current when the voltage drops.
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On Sun, 01 Aug 2010 15:24:23 -0400, snipped-for-privacy@snyder.on.ca wrote:

And most electronics (anything with regulated power supplies).
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The rated watts of a heating element is generally an estimation based on the typical outlet voltage divided by the resistance of the element. If the voltage goes down the resistance doesn't change (much) and so the wattage and amperage go down.
However...a microwave doesn't use a heating element as such. It does have a high voltage power supply which IS pretty sophisticated (controlled by solid state electronics) it may try to maintain a constant output power which would require a higher input amperage at a reduced input voltage. Or, it may only care about maintaining the correct frequency and let the power fluctuate with input voltage... I'm not sure which...
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The high voltage supply of a microwave oven is as simple as it gets. Just a transformer, diode and capacitor. Then the one tube magnetron. If the voltage drops, the heating power of the microwave goes down. It does not even care about the frequency all that much. Just a simple oscillator circuit.
The microwave ovens with the mechanical timers are about as simple as they come.
The only complicated electronics in the microwave is the ones with the electronic keypads for setting the clock and time. They are not really that much more than an alarm clock.
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On Sun, 1 Aug 2010 12:54:39 -0700 (PDT), Larry Fishel

type (newer high end) system may maintain the output, as does a regulated switch-mode type computer power supply .
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wrote:

Except the load usually behaves the other way. !500 watts at 120 volts, and 1250 watts at 110.

The OP wasn't running them together - they were on the same circuit, but he was ONLY running the Microwave - and the circuit breaker is by far the most likely problem.
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In

+1 Agreed. It's interesting how the guessers and faux experts climb out of the woodwork for electrical questions as though it were the safest, easiest thing in the world to understand and work with. The degeneration of this thread has gone far enough off base as to make choosing which responses are useful and which are not.
Twayne`
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Oops - I should have made it clear that only the instrument panel on the "regular oven" went out - IOW, the time of day and light bulb inside went out. This is a regular wall oven with two compartments. It doesn't pull anything to speak of.
The microwave oven is new - replaced only a few months ago.

OK, based on what I've read on this thread, and from my vast well of ignorance, I think it may, in fact, be a bad breaker. Note that I reported that in the past, MW only went out when used same time as other HEAT using devices (toaster oven; toaster).
Tx for your analysis.
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On Sun, 1 Aug 2010 21:46:23 -0700 (PDT), Higgs Boson

to malfunction (usually false trip), so if you've been kicking it by plugging in the toaster and the MW at the same time, that is likely what has happened. I'm assuming your "regular" oven is gas-fired???
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Wow. Um. Just wow. Do apples fall UP in your world?
James Watt and Georg Ohm are rolling over in their graves.
The power company doesn't reduce the voltage. The excessive strain put on the power grid is what causes the voltage to drop...
Amps don't increase when voltage drops, either. On simple resistive appliances, lower voltage causes lower Amps.
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This thread is full of misinformation. The power grid has reduced the voltage during periods of high demand. At the same time the frequency is slightly reduced from exactly 60 Hz. When the demand is reduced, the frequency is slightly above 60 Hz so the over all frequency will average 60 Hz over the long period of time. At this time the voltage will be slightly higher as the voltage is determined partly by the speed of the generators.
The power grid can not increase the amps. That is determined by the load of the grid. If the voltage is reduced, the current usually goes down for many devices.
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The best test is to clamp an ammeter on the circuit and see what it's drawing. If there is nothing on the circuit but the microwave being used, it's probably a bad microwave or breaker
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