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Is it dangerous to attach devices using more than 3680W in total to a single 16A/230V mains circuit or is all I risk triggering the circuit breaker?

Glorfindel
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    If the circuit breaker fails, you risk burning down your house. – The Photon Oct 30 '19 at 18:09
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    Erik, if the circuit breaker is working properly, it won't permit more than the stated current (plus or minus a little) to exist for long. There is a slight delay either designed in [or else accidentally included] which may be there to allow a momentary increase above the rating. But the gist is that it should flip if the rated current is exceeded for any substantial length of time (on the order of tens of seconds -- and not days!) If your breaker is NOT flipping and you ARE exceeding its rating, then you've got a different problem. Replace the relay! (Your wiring heats up and it's important.) – jonk Oct 30 '19 at 18:25
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    Since you mention 16a/230v I will only leave a comment. On the other side of the pond we use 80% of the breakers size to be fully loaded, the breaker is there to protect the insulation. If you overheat the wires the insulation gets soft and will melt then their is a short in the wall hopefully the breaker trips before a fire. I would not try to pull more than 16 amps in my case a 15 amp breaker is common most will trip at 17 amps within 15 minutes (I have to test some breakers for life safety requirements) the value of the overload changes with the ambient temp, works today but not tomorrow. – Ed Beal Oct 30 '19 at 20:34

2 Answers2

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The main purpose of circuit breakers is to protect wires in the walls from overheating. Even sprinkler systems cannot access wires in walls to put out the fire; the fire can become fully engaged.

You are messing up. You should not overload the circuit like that.

Your local government probably has provisioning standards for electrical supply. For instance in the US, we must provision power for 125% of continuous loads + 100% of loads not continuous. Many things such as a heater or EVSE are designated continuous loads even if they are not continuous.

So if I want to put a 1200VA water heater and an 800 VA garbage disposal on a circuit, I must provision 1200x1.25 + 800 = 2300 VA. That just limbos under the 2400VA capacity of a 120V/20A circuit, so it is alright.

Stay within the provisioning limits of the circuit. If you need more, either provision it or move the loads around physically to get them on different circuits. This is often a blindside of Bitcoin miners who want to put 10,000VA of miner all in one room (never mind the cooling problem that creates!) Spread them around the house so they are all on different circuits!

Trip curves

Circuit breakers have a designed trip curve. They will trip when current draw and time match the trip curve, with some tolerance.

enter image description here

This example (thanks Tester101) shows this breaker will:

  • at 2x rated current, trip between 9 and 35 seconds.

  • trip in 1 second with an overload between 4.5x and 8x.

These numbers vary due to manufacturing tolerances. Note that the Square D does not vouch that it won't trip at 100% load; it only says it'll take at least 300 seconds to trip.

You should look up the trip curve for your breaker. Its behavior should match this.

Harper - Reinstate Monica
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There's two main "bad things" you can do when overloading a circuit. If you short out the wires, a tremendous amount of current is drawn and the magnetic portion of the breaker will trip power very quickly. However, that momentary, huge rush of power will also go through all the connections between the short and the breaker panel. If any of those connections are weak, they can be damaged. It's not a great idea to "test" a breaker by touching wires together because of this.

The second thing you can do is overload the circuit with functioning devices. When this happens, there is a time delay (caused by heating) that will trip the breaker. If you draw 21A from a 20A breaker, it could take a while for it to trip. If you're just over the limit, it could even take hours. Continuous usage near the limit can also eventually trip a breaker. The more power you draw, the quicker it will trip. The same issue with weak connections still applies here and any weak connections will be troublesome.

So, to summarize, yes, the worst thing that should happen is the breaker will trip. If you happen to have a bad connection somewhere, this could cause it to fail.

JPhi1618
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