I'm working on adding a 7500W electric heater to my garage, and am wondering how to hook up an external double pole thermostat.
What is giving me some concern is that on the double pole thermostats I see they have an amp rating which is below the amp of my electric heater at 220V.
So my guess is that the double pole amp rating is for users who have in-line / series connected power to their electrical heating devices, but still want a graphical display?
I bought the Dyna Glow 7500W heater link
Here is the wiring diagram:
Because the thermostat is double pole, do I not need to worry about the current running to the thermostat?
My interpretation of the wire diagram and system intent, is that my external 220V double pole thermostat is going to be powered from L1 & L2 at 220V with 100mA or whatever low power (ie. the powered front end with the display with buttons) and then I hook up the "load" from the thermostat to 1 & 2 which then switches on the heater thermostat and the turn dial is set to max temp on the unit?
My thought is that the 1 & 2 line would be like 14 awg, and just carries some small current to the switch to activate the furnace thermostat to turn on?
Am I wrong? Will the ~31.5A be running through my double pole thermostat in someway and I need to find a heavier duty thermostat? (I understand if you have simple baseboard heater and you put a thermostat in series you have the current running through your thermostat).
I actually expected to see four wires on the external thermostat section with L1, L2, 1, and 2. When I pop open the furnance backplate will I find four wires or will I need to splice in 14 awg to L1 & L2 somehow too?
Am I totally off here? (Yep, I'd love to convert the 220V to 24V DC too and add the third Nest thermostat to the house, but first I want to make sure I understand the original intent of the wiring here!).
UPDATE: Here are the terminations and the thermostat.
Best Answer
That thermostat won't work with your heater without extra wiring
Your problem is that the thermostat you have won't work with your heater; in fact, no electronic line voltage thermostat will work with your heater if you wire it as depicted in the heater's wiring diagram, because that arrangement only provides a single line leg to the thermostat location, leaving the thermostat with no suitable path to return its own operating power back to the source. You'll either need to bring L2 over to the thermostat box as well with only the L1 side load wire connecting to the return to the heater, which requires running a 14/3 from the heater to the thermostat, or use an electromechanical thermostat instead of an electronic one. The good news is that the thermostat won't be switching much power, at least, so the wattage rating isn't critical.