On the photo below, you can see that the ground wire as burned.

Description of what i know:

  • the wire is connected on a 240V line to my baseboard heater
  • the wire seems to be a AWG 14/2
  • I don't know about the AMP of the wire. I cannot see it.
  • the breaker in the panel is a 20A that use 2 slots
  • The baseboard heater is a little 500W

I've just bought this house so i cannot tell if something wrong happened in the pass. Is it possible to test the wires with a tool to find reasons why it have burned? Maybe some data numbers will help me to find it out. Is it dangerous to put the baseboard heater back on this wire or should i open my wall and change the wire completely?

enter image description here

  • The burnt wire, is it a Neutral or Ground wire? Also, is the black or red insulation or the outer sheath brittle? What amperage heater is it and what gauge wire is it. It could be something as easy as a loose wire, arcing or maybe someone changed the heater out with a higher wattage style and didn't upgrade the wiring. Usually manufacturers account on normal building wire to be used around there heater so most of the time I would not think of the wire being burnt around the heater or inside the wiring compartment. Let us know on the other please.
    – lqlarry
    Commented Dec 18, 2011 at 23:25
  • You should probably run new wire. You may want to make sure that the breaker isn't a higher amperage than the wire can handle. (12 gauge 20 amps) (14 gauge 15 amps) U.S. Commented Dec 19, 2011 at 5:07
  • 2
    What size wire is it? Could it be undersized for a 240V heater (I ran 10 gauge wire for my baseboard heaters)?
    – auujay
    Commented Dec 19, 2011 at 5:56
  • i have updated the description of my installation. The wire is a 14/2 AWG on a 500W baseboard heater. Commented Dec 20, 2011 at 1:50

4 Answers 4


Burnt wires are usually the result of a loose connection. When a connection is not solid, wires can heat up. This can be an even bigger problem with high amperage devices (heater, stoves, etc.). This likely has been an issue for a long time, and finally reached the breaking point.

The problem with overheating wires, is that the issue becomes compounded over time. Through constant heating/cooling cycles, the connection can become looser, the wire can become brittle, and the resistance in the wire can be increased. The more the resistance of the wire increases, the hotter the wire gets. Eventually, the wire can get hot enough to burn off the insulation. When it gets to this point you hope the wire breaks causing a short (which will trip the breaker), or at least breaking the circuit so current can no longer flow. If the wire does not break, you could be in much bigger trouble if the wire gets hot enough to start a fire.

The fact that the ground is burnt, is concerning. Typically the ground should not be carrying current, and so should not be heating up. You'll want to check the heater for a ground fault, to figure out why current is flowing in the ground. Check to make sure the bare ground wires behind the thermostat are pushed to the back of the box, to prevent them from touching the bare terminals on the thermostat.

My advice to you, would be to contact a local licensed electrician. It's difficult to accurately diagnose issues like this, through the internet. An electrician will be able to explain the cause to you, and tell you what the options are to remedy this problem.


If there was lightning strike, that could have caused an arc across loose connections, including the grounding wire. But that is only one possible explanation among many. The suggestion of hiring a licensed electrician in answer #1 still applies. There are certain tests that can be done to figure this out, but these tests can be hazardous so I will not explain them here. The heater could have a short circuit between one of the insulated 120 volt wires, or any point in the heating element, and its case, compounding the hazards.


I did some Googling yesterday and there is a 12/2 NM style romex for baseboards made in the color red. Straight 240v, one red, one black and an undersized ground (I would imagine 14 ga) which would be good for around 4080 watts (240v x 20a = 4800W /85% = 4080 total allowable watts on 12 gauge wire). Check your watts and make sure your not over 4000 watts. If the wattage is over that then replace the wire. Too much amperage over extended time will cause the wire to start blistering and melting. If that is not the problem it looks like you can, if you have the room, cut off the bad part, if it's only the ground cut off that part and strip and tighten properly.

Since there is no 120v going to this make sure there are nothing operating at 120V on the heater. Thermostat should be 240v, but if its 120v, the you've got the wrong wire going to it.

  • If the heater was drawing too much current, why would the ground burn and not the hot wires?
    – Tester101
    Commented Dec 19, 2011 at 14:01
  • I think he is assuming the ground wire is smaller (14 ga instead of 12 ga)
    – auujay
    Commented Dec 19, 2011 at 17:42
  • 1
    @auujay it doesn't matter what size the ground is. There should be no current on ground, unless there's a fault.
    – Tester101
    Commented Dec 19, 2011 at 20:12
  • @Tester101: Right (I agree), assuming something was going wrong and there was current over both the ground and hot wires, the reason "the ground burn and not the hot wires" might be because it is smaller wire.
    – auujay
    Commented Dec 19, 2011 at 20:16
  • 2
    How many times has an 'ace of all trades' used a ground as a neutral and a neutral as a hot? I'm not an electrician but I hear them talk all day long. And some of the shoddy work is done by licensed people. In California a licensed general can do all work even if not licensed in electrical or plumbing or whatever. People get creative if it doesn't concern them after they leave.
    – lqlarry
    Commented Dec 20, 2011 at 1:55

There was a problem once, although it might have been lightning. One way to add a level of protection would be to add a GCFI receptacle or breaker to the circuit. If it blows, then you'll know there is a problem, and it might keep the heater from curling your hair.

  • GFCIs prevent people from being electrocuted, it would not help with a short or bad connection. An arc fault might be more appropriate.
    – Steven
    Commented Dec 22, 2011 at 1:50

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