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So I came home today to find my living room at over 80f degrees. My thermostat still correctly showed my base temp at 70f, but the room temp was through the roof and the ceiling heat was still going strong. I tried pulling the thermostat from the wall and disconnected the two wires so they dangle free, I left my place and came back a few hours later to find it feeling like I just opened a door to the Amazon jungle. I ended up shutting off all of the breakers since I didn't know which one the system was connected to and finally the room began to slowly cool down.

Now I'm stuck with no power and a ceiling that keeps heating, so there's some problem with the system itself. Unfortunately I found out the only company in the area that deals with these ceilings charges a ton because they know they can, and I'm just about fed up this and want to see if I can handle this myself before calling an overpriced professional. My questions are:

  1. Does anyone have any insight as to what the issue could be? I'm assuming it can't be too complex and should be simple to identify.
  2. How can I identify where the system is connected? If it's some drywall I have to cut open, is there an indication where that might be?
  3. Is it something that I can realistically do myself? I can go without electricity in that section for as long as it takes, and I have some experience wiring home electrical systems and general home renovation work.

I appreciate any help, which will in turn help anyone else in the building if I find out the work can be done without a pro.

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  • You mention that this is in a building with other residents. Is this a rental? If so get the landlord involved.
    – Michael Karas ♦
    Commented Nov 9, 2015 at 8:05
  • It's in a complex and I own the place, I contacted the head of the HOA and he told me about the company that deals with them. He's a good friend so I'm going to take his word that there's no other option, aside from hoping to fix it myself. On top of that, the building was built in the 60s and from what I read, these old radiant heat ceilings are a pain to deal with :(
    – user3625087
    Commented Nov 9, 2015 at 8:17
  • One place to look for the contactor is right AT the fuse/breaker box. There SHOULD be an access panel (junction box cover) if it's elsewhere, but only if Code was actually followed... On the third hand, decommission, put in a split system heat pump, and cut your heating bill by perhaps 2/3ds (.vs. electric resistance heat)
    – Ecnerwal
    Commented Nov 9, 2015 at 22:55

2 Answers 2

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Because they DO heat, I think that the problem is not in the heaters themselves, but in their thermostat or thermostat's probe.

What you need to do is to disconnect the heater element itself (the one on the ceiling) and connect a lightbulb (a real, incandescent bulb) in it's place. This way you can begin analyzing on when the panels are on and what to do to make them off, starting with what breaker they're on.

Your second step should be to map the entire system. Trace the wires, eg by switching off all breakers except the one controlling heater and tracing them with contactless voltage detector. The system must have 2 elements at least (heater and thermostat controlling it), but it can be much more sophisticated; eg thermostat can have remote probe or remote knob and the heating element can be controlled indirectly via a contactor. As you've said you've disconnected the thermostat, a stuck contactor is very likely cause. Replacing it is quite straightforward operation, IF you can locate and access it.

Another but radical solution is to ditch the old control system altogether and keep only the heaters themselves (of course AFTER confirming they work on mains voltage directly and old control system isn't doing some tricky power conversion). Then you get a brand new thermostat and a contactor(s) and set them up using new wiring at best. Probably best way do to new wiring is to keep the contactor in or near the breaker box and run two separate sets of wiring - one set (live and neutral for single phase / L1-N-L2 in case of 2phase / neutral + 3 live in case of 3phase) of power wires to the heaters controlled by the contactor and another set of control wires (live and neutral to power the thermostat + one live control wire back from the thermostat to drive the contactor - "control" but still operating on mains) to the thermostat. Or some fancy digital wireless system that would save you the wiring for the thermostat.

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  • I'll see if I can find how things are connected, everything seems to be pretty well hidden. I'll ask around the building to see if anyone has had any experience with the system themselves. Thanks a lot for the help!
    – user3625087
    Commented Nov 9, 2015 at 22:46
  • @user3625087 -- that'd be a good topic for the next HOA meeting, even :)
    – ThreePhaseEel
    Commented Nov 10, 2015 at 1:51
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in Oregon we have a lot of these the most common is the contacts weld shut on the contactor/relay most of these systems here are 220v and they only switch 1 leg usually the thermostats had the contact but it sounds like your thermostat is the controll for a relay/contactor it will probably be located in a metal box in the ceiling if you find it tap it it may brake loose but if it does it will stick again and will need to be replaced, make sure to turn the power off at the breaker pannel, it can be done by a home owner, also when working with the system be careful not to mess with the heat cable they are easily broken and then things get expensive as most splices are not rated for the heat these generate.

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  • Thanks so much for the info, I'll try to locate this box and see what I can find!
    – user3625087
    Commented Nov 9, 2015 at 22:45

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