how to thermal heat switch

[gghrt000]

i think so, it does not identify on the wall itself but looking at the diagram inside the cap, whateever two wires from one of the wall holes that are connected to two RED wires must be the LINE...(if you look at the pic above with the old thermostat cover)
If i had a voltmeter I'd rather measure:
between two LINE wires, there should be a voltage difference and between two LOAD wires there is none?
There is no other way around it.

 

[nealtw]

Usually line will be 1 red and 1 black and load will be 1 red and 1 black, they should come into the box paired like that. With the breakers turned off there is no continuity between the 2 load line wire and there is between the load wires. You can make a tester out of a flash light. If you have an old style flash light that the back end comes off hold one wire to the battery and the other to the metal strip that goes to the switch and turn on the flashlight. When the lightcomes on, you have continuity and you have found the load pair.

 

[gghrt000]

Guys i finally installed all 3 units into my wall, and tested 2 of them working since one of the heater is shot. I had to turn all the way you to 75 degrees for the heater to start heading up. I presume it is because hot day?? That let me to believe perhaps it is aware of current ambient temperature?? Also I might need to touch on the wall around the visinity a bit as I have been scrubbing dragging the wires and stuff along the wall as I am working. Last of all thanks giving me a invaluable info.