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My home has two sets of circuit breakers, one in my apartment, and one in a shared area downstairs (these are switches that pop up with another one or two nearby buttons that also pop open when there is an electrical overload due to too many appliances turned on). Wikipedia states: "circuit breaker: an automatic device for stopping the flow of current in an electric circuit as a safety measure."

So, my question is, why have a circuit breaker upstairs and one downstairs instead of just one?

Thanks.

So, since I'm interested in the wiring inside as home, and voltage inside homes here is fixed (in my case 220-240 V), current equals load. The case would be different if I was considering a circuit where the voltage within the circuit would change with time. Correct me if I'm wrong.

Circuit breaker downstairs

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    You can't upload images at this point to avoid spambots abusing the feature. Once you have some reputation build up from upvotes you will be able to add images to your posts. – ratchet freak Sep 14 '17 at 14:16
  • If you have a photo of the situation, upload it somewhere, provide a link to it in a comment (here) and someone will edit it into your question. – wallyk Sep 21 '17 at 6:18
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Circuit breakers protect the wiring in the home from starting fires due to overheating, because when a fire starts in the walls, you can't put it out because you can't reach it, and the house is done for. Overheating is caused by overload. The purpose is not to punish people who enjoy electrical appliances.

It is not the number of appliances, but the sum of their current draws per circuit. You can't run 2 kettles, but you can charge 100 iPhones.

(If you want to wire a kitchen so you can use 2 kettles, coffeemaker, hot plate, grill, sous vide, toaster and microwave all at once, that's no problem, just wire a separate circuit to every socket. That's why they make 12/2/2 cable.)

Why are there separate breaker panels?

  • To avoid Tenant A having to ask Tenant B to reset their circuit breaker, because that begets ugly hacks like extension cords under rugs, which begets house fires. The Electrical code is written by the National Fire Prevention Association.

  • So that Tenant A cannot shut off Tenant B's power, either by accident or as a prank.

  • In many jurisdictions, it's a legal requirement that loads in commons space must be separately metered, i.e. One tenant can't get socked with the bill. A lot of legacy installations are grandfathered, but then, they have to fix it when they remodel.

  • Well, if tenant A wants to shut off tenant B's power, can't tenant A just go downstairs and push down the switches on tenant B's circuit breaker? Aren't the circuit breakers upstairs and downstairs connected in series? – Jimmy Joslington Sep 21 '17 at 6:13
  • @user162949 I'd have to know the size of the circuit breakers to understand that exact setup. – Harper - Reinstate Monica Sep 21 '17 at 6:16
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Local building codes will always want the party occupying a space to have access to their own overcurrent protection for obvious reasons.

  • So why include one downstairs as well? Is it a safety feature? Thanks. – Jimmy Joslington Sep 20 '17 at 20:19
  • What are the obvious reasons for wanting one's own overcurrent protection other than one may want to turn off the current from there as a safety measure when working on a wire or changing a light bulb? Thanks. – Jimmy Joslington Sep 21 '17 at 5:26

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