Is this line voltage thermostat sufficient?

Question

I'm replacing a bad Aube line voltage thermostat for my electric baseboard heaters. I liked the model, so I purchased what I thought was the same one - however I missed a letter in the model. What I bought was a TH115-A-240D, while what I had originally was a TH115-A-240S. It looks like the difference is that the TH115-A-240S was rated for 4000 watts, while the TH115-A-240D is only rated for 3600. As far as I can tell, however, the new one is still sufficient. I'm just hoping someone can double check me.

There are 2 baseboard heaters, wired in parallel, on a 20-amp 240 volt circuit. The wiring is #12. Each baseboard is 72 inches. Unfortunately I can't find any manufacturer's information anywhere on them (I believe it's all painted over.) Everything that I can find indicates that a 72-inch electric baseboard heater will consume 1500 watts, meaning that the total 3000 needed by 2 is well within the thermostat's specs. Is there any caveat I might be missing, or should I be safe?

DAS · Answer

Six-foot baseboard heaters are sold in varying voltage and wattages. You can buy a 1250 watt, 1500 or even 2-3000 watt heaters in the six foot lengths. So, I would not assume anything about your old heaters. On a 20-amp circuit, you can have a maximum of  3850  watts. So, you might be within that limit, you might not. There's my caveat. So if you're installing exactly what you had, you could be "safe".
See this chart https://king-electric.com/pro-tips/sizing-the-heater-circuit/

user263983 · Answer

Simple multimeter, ohmmeter can help you. Resistance of heater don't change too much over temperature. Simple calculation for power U^2/R. Or current consumption can be measured with current clamps. Every electrician has that kind of tool. Overload may cause thermostat contact degradation and it will be damageded over some time.

Answered by user263983 on July 22, 2021

Is this line voltage thermostat sufficient?

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