Odd tripping breaker

[Ken Tannenbaum1]

I've a 20amp breaker servicing a toaster oven and microwave. Very often, both are used at the same time, and that will go on for weeks with no problem. However, about five or six times per year, turning on the microwave alone will trip the breaker. Any clue why?

 

[Reach4]

Possibly when the breaker is on the verge of tripping, there is sometimes a vibration that puts it over the edge.

Maybe the voltage to the house is higher at times, causing the appliances to draw more current.

 

[Sponsor]

 

[Ken Tannenbaum1]

Any way breakers break down, actually weaken? It's the only breaker it ever happens to. Thanks so much.

 

[Reach4]

Any way breakers break down, actually weaken? It's the only breaker it ever happens to. Thanks so much.

Yes, but when you add up the amps from the two devices, I expect the total is significantly more than 20 amps. Those are two high-power appliances, and usually they would not be put on the same circuit. New code calls for at least two circuits for kitchen outlets.

If it bothers you, consider adding a new circuit to the kitchen.

 

[Ken Tannenbaum1]

Thanks...but...as mentioned, it has never, not once, tripped while using both appliances.

 

[Reach4]

Thanks...but...as mentioned, it has never, not once, tripped while using both appliances.

Sorry. I mis-read. Swap the breaker. Many are pretty cheap.

 

[Ken Tannenbaum1]

Me too, happens all the time. I'm going to switch out the breaker, see what happens. I read they can go bad. Thanks again.

 

[Jadnashua]

Most breakers do not trip immediately unless the overload is significantly over their rating. IOW, it can take some time. Those times it trips may be when you're using a higher setting in the toaster oven, and it needs to be heating longer. The things do wear out, and it happens more often if they are used near their peak rating than say one used to light a lamp.

FWIW, raising the voltage tends to LOWER the amps, not raise it on most heating loads. On a heating element, as it gets hotter, it's resistance goes up, so it is somewhat self limiting on the amount of current it will draw, thus limiting the current that will pass through it unless the voltage gets way out of spec. This is one reason why brownouts can be worse than higher voltages as the current needs to go up to provide the same power.

 

[Dana]

With resistance heating loads increasing the voltage still increases the current, despite the higher resistance of the hotter temperature. The increasing resistance with temperature just means that it's not a strictly linear ohms-law increase in current, but it's an increase nonetheless.

With some types of motors and nearly all switching power supplies current increases inversely with voltage.

 

[hj]

quote; some types of motors and nearly all switching power supplies current increases inversely with voltage.

IN other words, you are saying that the wattage stays somewhat constant.

 

[Dana]

quote; some types of motors and nearly all switching power supplies current increases inversely with voltage.

IN other words, you are saying that the wattage stays somewhat constant.

With switching power supplies, yes, the wattage stays somewhat constant. With motors that's often NOT true. (But with ECM-drive motors that can be the case.)

 

[Kreemoweet]

Not only do breakers "go bad", it is also possible the breaker was defective to start with. There's little doubt
that there are (at least) hundreds of thousands of counterfeit circuit breakers installed in this country.
What specs (if any) they were manufactured to meet is a matter of conjecture.