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I have several 3d printers. One of them keeps tripping the breaker for the room. I'm trying to debug (obviously will not use it regularly until I can determine what is wrong) but in the mean time I need to keep my other printers running.

A power strip's breaker isn't enough for it to trip, so it's drawing less than 15 amps when it spikes. It also draws 50 watts when just running normally. The breaker for the room is 20 amps, but I'm running an AC and various other appliances as well. The combination is what causes it to trip the 20 amp. It's absolutely not the AC causing it to trip. I have eliminated variables and it's one of the 3d printers for absolutely certain.

I'm guessing I need between a 3 and 5 amp resettable breaker, one that works for a single outlet only. 120V.

Where can I buy such a breaker?

Would be even nicer if I could switch between a few different preset values, ie, 3 amp, 4 amp, 5 amp, etc.

My workshop only has one circuit, just how the building is set up. (rather each room has one circuit, I only have access to the room I pay for)

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  • \$\begingroup\$ heaters are regulated slowly so when all are on, these can peak your drain \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Aug 30 '17 at 22:33
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    \$\begingroup\$ You have \$20\:\textrm{A}\$ for the entire room. I think you said that you tested one printer to make sure that it is below \$15\:\textrm{A}\$. But you admit there are other printers and other devices in the room. The room breaker will trip when the total exceeds its limit. You will have to run fewer devices. You cannot "ADD" a breaker inside the room in order to add to the compliance limit of your room's breaker. That's just silly. I think you want a better service. Find another room with a higher compliance capacity for your equipment. \$\endgroup\$ – jonk Aug 30 '17 at 22:42
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    \$\begingroup\$ I think you are misunderstanding. I am running servers and such that total 7 amps or so. All printers total are below 15 amps also, ie, the power strip doesn't trip. But when the printers hit 14 amps, that is more than 20 so the room blows. I want each printer to shut off on its own if it pulls more than 3-5 amps. The 20 amp capacity of the room is not relevant as if any printer pulls more than 3-5, it's faulty. \$\endgroup\$ – user161487 Aug 30 '17 at 22:47
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This is complicated since the downstream breaker must be faster then the upstream breakers. It needs to have different time characteristics.

This is called breaker selectivity.

Without replacing upstream breakers, you'd probably need a breaker that is so sensitive that you can't even enable the breaker. The inrush would trip it immediately.

Also, a 20A breaker won't trip immediately at 21A. This will take minutes. See the image in this post.
I think you have a larger overload.

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You can buy low current panel mount circuit breakers from Digikey and other electronic suppliers. You could mount one of these breakers and an outlet in a box to produce individual low-current outlets for your printers.

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I don't know about the US, but here in the UK I would go to the local hardware store where I could find a consumer unit (I believe the standard term for such an item in the US is a distribution board?) along with a 6A breaker that's designed for lighting a garage, such as this one. Wiring it up is pretty simple, and you can then enjoy protected outlets that won't cause your main circuit breaker to trip. You also get an individual RCD (ground fault breaker) for your circuit too.

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