I was just doing some investigating to my home's electrical setup, on curiosity. I noticed that I have a room with two electric heat panels, each rated at 2548W. They are on 12AWG wire, and a 20A breaker. I did the math, and came up with a total current draw of 21.23A. How come my breaker isn't tripping? And is this a fire hazard?
I am curious in how you can have a 2548W heater, unless it’s an older heater. On a 120V household circuit the max wattage for an electrical heater is 1500W. But the reason that your breaker isn’t tripping is because of the way that breakers are made. They will only instantly trip on either 4 or 10 times the current, a load that is close to rated will only cause it to trip after a period of time. According to the NEC AWG 12 is limited to 20A but it’s kind of screwy on the fact that it does list it’s capacity at 30A. Either way that very easily could be a fire hazard given the fact that an electric heater itself will not only get hot enough to ignite things the wires feeding them also get hot and if it’s an extension cord those are usually buried under a rug or another flammable thing. Some more information is needed to see if this is a fire hazard.
it's marginal. But really rated at 2548 watts? usually they are rated at a more even number, as the power rating is not that exact, certainly not to 1 part in 2000. Where did you get this number? Similarly 21.23 amps is too exact for the conditions. also, your voltage could be lower than 120 volts, which lowers the current. So this is a homework problem? 20 amp breakers will trip very fast for a 100 amp oveload, and fairly fast for, say 30 amps. But for a value only 8% over the limit? they may never trip. Again, it's marginal, but OK. I'd want a better reading on the power rating of the heaters, and the voltage rating. .
A household circuit breaker has a trip time characteristic that is a function of current. The higher the current, the faster it trips. A 20A breaker may well never trip at 21.23 A. There is considerable conservatism in the wire rating too. A 20A breaker is appropriate for 12 AWG wire per the National Electric Code. I do not think you are in danger. Also the heat panels presumably cycle on and off to maintain temperature so they are not continuously on. This will help the situation too.
