On a service call the other day I found a thermostat ( Caded model C2002, UL5C86, 240V, 22A max, single pole) that caught fire in the middle of the night. Luckily the owner was able to put it out. Somebody replaced one of the baseboards in living room with a 3,000W fan driven heater which increased the total load on the thermostat to 4,500W (or 18.75A )on a 20A circuit. I always load the heating circuits at no more than 80% or 16A in this case, but even 18.75A was well within the thermostat rating of 22A max. I tend to believe that the short happened in the electronic circuitry inside the thermostat ( poor heat dissipation? ) To make a long story short, the problems were corrected but I wander if anybody had similar experiences/what thermostats do you use?
22A x .80 = 17.6A Alternatly 18.75A x 1.25 = 23.4375A Either way the thermostat became too small when the new heater was installed. Of course the circuit is now also too small for the load. Good luck with the fix.
Paxman, I would side with nesparky on this one, but, the person who changed the heaters over, should have checked this before-hand!. I have had Thermostats burn-out on me before, but not as destructively as that, it must be the internals that got way too hot. There was nothing blocking the small vents on the Thermostat, was there?.
Hey, it could've been one of those "handyman special" type job... which reminds me of another situation I found while doing a service change - a handyman installed a 3,000W heater in each bedroom and then slapped in a 30A breaker because the 20A one kept tripping. Talk about a fire waiting to happen. In this case I did replaced the other two thermostats in bedrooms because they also showed signs of overheating. Vents were not obstructed by anything.
Good point mate, I only use quality Thermostats(Honeywell). If you are ever in doubt, about a Thermostat, use it to switch a Contactor, at the Switch-board.
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