I have a 1000w, 750w heater and 3 100w bulbs on the same circuit and it will not flip the breaker. If I crank up the 750w htr to 1500 it flips. Same issue on other 15a circuits so it's not the breaker. Shouldn't the breaker flip at 1800w? (15x120)
It should, but the overload is so small that it might take a while. And... many electrical devices don't draw what the nameplate says; unless you have actually measured the amps on your heaters, they could be way off.
Give it more time, perhaps much more time. I read that breakers typically allow a 10% overload for at least 10 minutes. After 3 hours, they should trip at their indicated rating or even a little below that.
-- Mark Kent, WA
The power ratings on most appliances are, at best, approximations and on heaters they seem to represent a worst-case number. And don't forget that even a seemingly minor change in line voltage can cause a serious change in power dissipation. Example: a 1200W/120V heater will drop to ~1100W when run on 115V and voltage variations like this aren't that uncommon. The only way to know how much power a particular appliance is consuming is to run it though an accurate power meter.
the breaker heats up. when a certain temperature is reached, it disconnects.
if you draw a large ammount of current (heater at 1500) it heats up faster than if you draw lower current (heater at 750). it will still heat up and trip eventually, jst not right away.
This is Turtle.
1) A breaker can trip anytime it gets ready to for all conditions of area air temp., wire size / rating and length, breaker age, correct voltage being used / most voltages to homes in my area are 124 volts, and last the exact amp rating of the heater your using at different speeds will be a big factor in when it will trip. If it was a perfect world and everything was the same. your thought pattern above would be in line to estimate the draw amps / watts. Without a amp meter to put on the circuit to see the exact amps the system is drawing -------------- i will try to give you a answer of some kind.2) The rating of the breaker as amps/watts go as to the most you should put on the breaker. 15 Amp breaker / # 14/2 wire / less than 50 feet run /
124 volts service to breaker / Breaker in good condition / Wire and breaker area temperature less than 60ºC / all connections are good and no circuit in ill repair ------ The breaker should not trip on 1,488 watts / 12 amps or less.3) Now by your calculations your drawing 1,500 watts and this is over the limit of the breaker by a very small amount. The Manufactor of the breaker , NEC Code , and any electrician looking at it will say your over the limit of the breaker -- Period .
4) Now i will say this : By you not being but such a small amout over , most all good breaker will not trip at such a small amount over the limit. You should check the exact amp / watt draw with a amp meter on the circuit to see that your not off on the amount of amps / watts your drawing and just change out the breaker if your really not over but such a small amount on the amps / watts your drawing for a good breaker should not trip on a small amount over on the amps / watts your drawing.5) If wire , voltage, breaker, and conditions are different from what is stated above here. Disreguard all the above.
TURTLE
The power rating of an appliance would "usually" be the most power it would use at the rated voltage. Without a meter, you do not really know.
Also a breaker is not an electronic device that trips the instant you hit
15.1 amps. They are more like a slow blow fuse, so somewhat higher than normal momentary starting currents will not trip them, but a direct short or sustained overload would.An oil filled heater I have is supposed to be 700+800 watts, but is really
600+700 (1300 total). A different 1500/900 ceramic heater temporarily starts out at 1800 watts (making 15 amp rated "Kill A Watt" meter beep), but gradually drops to its 1500 watt rating (resistance increases with temperature). The latter did work fine on a 15 amp breaker, but would I normally have it on a 20 amp dedicated room AC cicuitI bought the oil filled heater from my boss after he realized that he could not run 2 such heaters on the same circuit to heat his garage (over
20 amps).Thanks for your detailed reply.
Would it be unsafe to use a 20a breaker with 14/2?
Martik posted for all of us....
Yes, per the NEC
yes, since the 20A breaker will not trip at currents that are above the rating of the 14/2 wire. the wire could heat up and in time cause an electrical fire.
This is Turtle.
I look on my wire amp / size wire Chart and # 14/2 is rated for 15 amps. I look at # 12/2 and it's rated at 20 amps. You are suppose to rate the breaker to match the size of wire you have. If you get down to brass tacks there is loop holes in the NEC to allow the #14/2 to hook to a 20 amp breaker but you better know what your doing to do so. Do as you please.
Now here is what I think here. Don't put 20 amp breaker on # 14/2 wire. The
20 amp breaker goes on # 12/2 wire and 15 amp breaker goes on # 14/2 wire. I always error on the safe side.TURTLE
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