I have a 1KW panel heater that I'd like to control with a remote electronic thermostat. Thermostat switch contacts are rated 5A 250V resistive and 3.5A 250V inductive. Should I consider the heater a resistive or inductive load??
TIA
Its a resistive load but I'd guess that a 5A switch is not enough.
Assuming 230 volts supply, the heater will draw 4 and a third amps
Thats a bit close for me.
I could and probably will be wrong
fray
It's mainly resistive but like all heating elements and filament lights will have a much lower cold resistance than the hot one, so will draw more current than its working rating at switch on. Which I'd guess would be dangerously close to the thermostat's maximum. You could measure the cold resistance and work it out, though.
Most heaters don't have any switch-on surge -- temperature coefficient of Nichrome is pretty near zero (as compared with tungsten anyway), and it's not normally heated through the same temperature change either.
Hi Whew whatever happened to manufacturers putting 5A dc 3.5A ac on their switches. As for your heater its impedence depends on the manufacturing process some panel heaters have a punched strip (looks like a row of hairgrips on a plate) these have a lower impedence compared to the coil wound fan panel heaters. In any case i would recommend a 10 or 13A rated stat due to the start surge of the heater and the back EMF at switch off under load.
HTH
CJ
Just because we atheists don't believe in him doesn't mean he doesn't exist.
Over 20 years ago, I bought a bathroom fan heater (Dimplex). Although it was set down to just 1kW (could be set to 1kW or 2kW at installation time), the integral pull cord switch burned out in about 3 months. I cleaned up the switch and fitted a small contactor into a cavity inside the heater which was for a shaver isolating transformer in a different heater model, with the switch operating just the contactor. It's been running fine ever since. Apart from the inadequate switch, it was very well built.
In article , Andrew Gabriel writes
Fan motor - now that's a candidate for both inrush and back emf.
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