AndyC_772 wrote:A triac won't reduce the voltage - they're used to turn the supply off entirely for complete cycles.
While I agree with Andy,Funny, we must be living on different planets...
jremington wrote:Yes a triac will work, however, the fix sounds like a potentially serious fire hazard. ... If the triac circuit should fail and allow full AC supply voltage across the compromised heating element, all of the above could take place. Best to get a new mat.I agree - triac dimmers usually fail "always on" (this has happened to several in houses I've owned) so it's just too risky IMO. If you really need to do this, I'd suggest using a transformer in an autotransformer configuration, as it will be a lot smaller (you could use a 500VA transformer instead of an 1800VA unit). Partly re-winding a toroidal transformer might be the way to go, if you know what you're doing.
jremington wrote:...potentially serious fire hazard. ...insulation could melt and/or burn and short circuits could lower the resistance further, leading to catastrophic failure.With or without triac, you definitely need an appropriatedly rated fuse (takes care of short circuits...remember? ) plus an overtemperature protection embedded in the flooring. A winding thermostat as used in electric motors, for example. Use a contactor to control the whole thing, and should the thermostat trip, it shuts the contactor off and you can then manually restart the heater. That way a triac is safe to use (and much more convenient than a bulky, humming transformer full of valuable copper 8) )