Latest Discussions : Electrical & Lighting


10:32AM | 12/15/08
Member Since: 12/14/08
2 lifetime posts
Upon accessing a licensed electrician installed junction box, I found that one of the lines that powers a bdrm baseboard heater to be 12 ga. instead the 10 ga. that is used on all the other heater circuits. This particular line is connected to a 500 watt, 2.5 amp heater (the other heater in the room is identical, except that it is connected with 10 ga.). Is this safe? I know that 12 ga. is only rated for 20 amps & that this is a 30 amp (double) circuit, but the load is way under capacity. It has been connected for over 20 years without a problem, but I would like some assurance that this setup (not up to code I'm sure) is OK before I re-connect the junctions. Any help would be greatly appreciated.


11:02AM | 12/15/08
Member Since: 12/27/06
14 lifetime posts
Usually Baseboard heaters are 20 AMP circuits. You'll have to check the Amperage rating on the baseboard heater to be sure. My guess would be it's under a 20 AMP, but who ever wired it just tossed what ever breaker they had available at the time. If the Baseboard heater is under 20 amps, you can just replace the 30 AMP breaker with a 20 AMP one. Although in theory the baseboard heater could require a 30 amp breaker, it's unlikely. Even 10 foot long Baseboard heaters are rated for 2500 watts, well below the 3800 watts 12-2 is rated for. (At 240v)


11:08AM | 12/15/08
Member Since: 12/27/06
14 lifetime posts
Sorry I misread your original post. You already stated what the Wattage and Amperage of the Heater was. Turn off the 30 amp breaker and add up all the heaters that are on that circuit. So long as the total draw for all of them is under 3800 watts, then a 20 AMP breaker using 12-2 wire is perfectly fine. Your allowed to overrate the wiring by code, it's when they are underrated is when they are a problem.


11:57AM | 12/15/08
Member Since: 12/14/08
2 lifetime posts
The heaters are 5oo watts and draw 2.08 amps @240v . Even though I don't need the 30 amp circuit for that low of a draw, is there any problem with keeping it the way that it is (saves money). Also, for clarification, the line bringing power to the junction box is 10 ga. Connected to that are the two bdrm heaters (one 12 ga. & the other 10 ga.). Under the above conditions this does not present a safety hazard. Is this correct?


12:49PM | 12/20/08
Member Since: 01/09/07
199 lifetime posts
If I am understanding this correctly, you have a 30A breaker in the breaker box, #10 wire from that to a junction box, then in the junction box you have 2 cables, each going to a 2500W baseboard heater, with one cable being #10 wires and the other #12 wires. Right?

Then that is NOT up to code! You have a 30A breaker on a circuit where part of the wiring is #12 rather than #10. The breaker is too big for the #12 part of the circuit, and would not provide protection. It would only trip at 30A, but the #12 wire part of the circuit is only rated to handle 20A. So if someday someone replaced that 2500W heater with something drawing more than 20A, the #12 wires could overheat, but the 30A breaker would NOT trip. So that is unsafe!

In practice, it's not real dangerous right now -- you only have 2500W running through that circuit, and the #12 wires can easily handle that. But if you had a short in that heater, the wires could overheat and start a fire before the breaker tripped. Not good!

There are 2 ways to fix this:

1) replace the 30A breaker with a 20A one, to match the weakest (#12) wires in the circuit. Should be no problem with that, because your load from both heaters is still under 20A.

2) Leave the 30A breaker, and replace that section of #12 wire with #10, which can handle a 30A load. But that may be more work than just changing a breaker in the breaker box.


04:51AM | 02/26/21
If anyone reads this in the future 2021 foreward. There are tapping rules that allows smaller wire for the last heaters on these circuits. It is possible this is what was installed.

Post a reply as Anonymous

Photo must be in JPG, GIF or PNG format and less than 5MB.

Reply choose button


Post new button or Login button