Radiant Heating in Ceiling over voltage

[doran4x]

I have a ceiling radiant heating system in an apartment building I do repair work in. The building was built in the late sixties or early seventies. In one apartment the living room heat is bad. The square footage is 500 sq. ft. +/-. I get a reading of 28 amps on each leg (240 volt). The feed wire is #12. Thermostat is 2 ft. from panel. The wire leaving thermostat to ceiling is #12. Does anyone know what the amps per square ft. should be or what the cause of this over voltage is. The system has been checked for breaks and there are none. I will not install a 30 amp breaker (per the radiant heat specialist) as the wire is #12 unless someone can tell me different. The two bedrooms are 260 +/- sq.ft. and run +/- 8 amps each.

Thanks

Tom

 

[Sierrasparky]

I wonder if somone has shortend the amount of wire being heated. Ie an accidental cut in the heat cable. This could reduce the resistance and increase the current.

 

[BILMC]

radiant ceiling heat overvoltage

radiant ceiling heat overvoltage

One of my customers has radiant ceiling heat installed 1967/1968, all on 240 volt 20 amp breakers, the largest celing zone draws 22 amps and eats one thermostat per year. It is my speculation the panel was origionally designed for 220 volts . I have had the utility come out and check this out, but they prefer not to reset transformer taps because the other loads will not be served well with anything less than the 240/245 volts as it now stands. this panel megohms OK, but I cant be absolutely sure it has never been tampered with. The solution we have in place is to research thermostats for maximum heat sink and durability. If they continue to fail we are considering a low
voltage thermostat controlling a 25/30 amp. relay. any other ideas?