#20 amp breaker full#
If it were a "soft" steady load like a heater or lights, it would probably hold 20+ amps, but the surge of welding is probably too much for it once it heats up.Those specs are usually a little misleading - 20 amps is not at full load. Either reduce duty cycle, or upsize wire and breaker. You are probably tripping its thermal overload. They have a current surge trip function (closer to 26-30 amps) and a thermal process (time based) for the de-rate I mentioned before. If you pull 20 amps through a 20 amp breaker for more than a few minutes, it will often trip. I looked up the specs of this welder, If it's like this one : it's going to pull 20 amps at full load. Just putting that out there for the learning opportunity. Assuming your welder is just a transformer based machine, I doubt this is going to be a problem. The worse it got, the more current the active supply (load) pulled to compensate for the voltage loss, the more the connection got hot from increased current, and quickly failed in a very bad way.
I've seen electrical fires result when there was a minor connection problem that couldn't carry the load. Those will pull more current when voltage drop occurs to deliver a constant power. If the welder (or any other load) has an "active" power supply with voltage compensation, this all changes. If it's merely a little warm, that's fine. Check the wire with your hand just after a trip, is it hot, or more than just warm? You need to upsize conductor. If you are getting your wires warm, you are not delivering all the energy to the load. Current is what heats the wire, not the voltage drop. The difference is there is less voltage drop on a 15' run, so you deliver more energy to the load on a shorter run. Since current through the entire circuit is equal regardless of load or wire length (loss), 20 amps will burn a 15' wire just as badly as it will a 150' wire. Almost every rule in the NEC has exceptions. High dutycycle loads require an 80% de-rate in the NEC, so a 20 amp breaker (12 gage conductor) is only rated for 16 amps continuous. That said, I've been quite successful using one size larger breaker on a given conductor, but I do so knowing it's a risk, and that I need to keep duty cycle down. They also allow for far more heat and voltage drop than I find acceptable. The NEC is also assuming a long run in the house of 80-100', and there are different charts for different wire temp ranges. It's all thermal calculations and based on fire prevention. The breakers purpose is to protect the wire from overheating, and has nothing to do with what is after the outlet. Even just moving (swapping) with another spot in the panel to test the theory would be easy and informative. perhaps replace the breaker with another of the same type first. It's not uncommon for a tired 20 Amp breaker to trip at 15. Breakers also get tired and warn out from frequent abuse.