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I would like to install some additional appliances in a room that already has a couple of heavy equipment machines running in it. These are sensitive machines, so instead of having the main circuit breaker trip when there is an overload, is there a device that I could connect to the outlet and then connect the new appliances to these devices? My goal would be to have power to these specific appliances cut off instead of tripping the breaker.

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  • \$\begingroup\$ Not enough information. You write about "heavy equipment" that suggests high current and perhaps intermittent high currents. But you don't actually say that. Maybe so, maybe not. Then you write about "sensitive machines" but nothing about their current requirements, which so far as we know may be only a little or a lot. Then you ask us for a solution. I think we deserve a LOT more information/details. \$\endgroup\$
    – jonk
    Oct 27 '20 at 4:08
  • \$\begingroup\$ Sure there is. They're called...wait for it...circuit breakers! Maybe you've heard of then. Specifically, they're called downstream circuit breakers which are just smaller breakers. Easy enough to mount a bunch of them on a DIN rail and connect a AC jack and AC plug to them, though I do not know what an electrician code would require. \$\endgroup\$
    – DKNguyen
    Oct 27 '20 at 4:30
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The only viable solution is to add another circuit with its own breaker for the sensitive machines and NEVER MESS with a circuit breaker, its function is to PROTECT!

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If you load is a motor, a VFD could be this device where you can set the max current.

I have used it myself on an asynchronous machine which was more than capable of pulling more current under high load than my utility company's service would allow and thus melt the fuses.

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It is standard practice to have a main circuit breaker, followed by supplementary circuit breakers, to feed the branch circuits catering to individual machines.

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The breakers are to be appropriately sized.

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It is about what we call discriminative tripping. divised into both:

  • current-level discrimination
  • time-based discrimination

The type of the circuit breaker defines the tripping. For type B, for instance, the current is 3 to 5 times the rated current for a time between 0.04 to 13 seconds. You can find the curve for each circuit breaker (inverse time curve).

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