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Imagine, hypothetically, that despite being told not to, someone keeps using a hair dryer and space heater in the same outlet at the same time, and thus tripping the circuit breaker. Will this have any detrimental long-term effects on the breaker, wiring, or anything else? Or is it fine to just keep resetting the breaker as many times as it takes them to learn?

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The breaker is designed to heat up at about the same rate as the wiring in the walls. However it tends to cool off much quicker than wiring in walls. It's expected you are going to leave the breaker off and resolve the underlying problem, not reset it over and over.

So if it is frequently reset, the wiring gets hotter and hotter and the breaker is out of sync with just how hot it is. This can lead to a fire.

A typical hair dryer is 1500W or 1800W. Almost any space heater is 1500W. However many space heaters have a "low" setting in the 700W ballpark.

A 15A circuit has 1800 watts.
A 20A circuit has 2400 watts.
Neither one can support two 1500W devices.

Nonetheless, rather than blaming the user, you should consider that technology is meant to serve us, not the other way 'round. The user's requirements are reasonable, and the technology should meet it.

The real culprit here is a single 15A or 20A circuit supplying power in the bathroom, and possibly serving other rooms as well. It's true that NEC allows bathrooms to be served by one 20A circuit, but you are certainly allowed to have 2 circuits in a bathroom - and that's the best cure for 2 heat appliances at once.

However, even better would be to dump the dangerous space heater and get built-in 240V heating, such as a baseboard.

A simpler method would be to obtain a space heater with a low/high setting, and either educate the user on use of the "low" setting with the hair dryer, or hack the space heater so the "high" setting gives the "low" setting.

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    I meant a few days between trips, not resetting it without unplugging one and letting it trip again immediately. Dec 12, 2021 at 14:00
  • @JosephSible-ReinstateMonica you didn't say, but it doesn't surprise me. A 15A breaker will take a minute or two to trip on a 25A (167%) load. A 20A breaker will take much longer to trip on a 25A (125%) load, if at all -- a breaker that fails to trip on 125% load is still within UL specification of 135%. Still, the space heaters should be sharply discouraged. They're dangerous. I would install a 240V baseboard or wall heater with a manual wind-down timer switch (since they work on 240V, pushbutton timers do not). Dec 12, 2021 at 23:11
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I'm not an electrician, but I play one on TV. Constant breaker flipping may eventually wear out the breaker, causing it to not work and potentially cause a fire by overheating the circuit, which includes the wires, switches, breakers and anything else plugged into it and nearby.

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  • Do think most breakers have fail off than a fail on, design.
    – crip659
    Dec 11, 2021 at 1:49
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Breakers, like any other device, wear out. There are latches in them that will get rounded out and not lock in place when being reset. If the two devices you're referring to are plugged into the same outlet, the constant overloading will weaken the jaws of the outlet. Breakers don't trip immediately on an overload, they "cook" a little bit and tht overload can/will eventually damage the outlet.

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  • And is that going to take e.g 100 or 100,000 cycles to do that? Dec 11, 2021 at 3:58
  • Or just a few. Electrician was doing some work needing the main breaker to be turned off. When work was finished, main breaker did not turn on. Good thing it happen when the electrician was there, he had a breaker and just undid the meter(was friendly with hydro).
    – crip659
    Dec 11, 2021 at 10:47
  • @whatsisname Who knows, but I've replaced many that wouldn't hold a reset. There's also the thermal part to consider as it weakens from the constant overload/tripping.
    – JACK
    Dec 11, 2021 at 13:05
  • @crip659 I replaced a main breaker after a few years that just started tripping for no reason... it had never been overloaded or used for switching.
    – JACK
    Dec 11, 2021 at 13:07

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