Since you are working with a double pole thermostat there should be four wires.
How to install a double pole wall mount thermostat.
Two of these are live wires and two are load wires.
Make sure to connect the ground to the thermostat or wiring box if available.
It is usually attached to the wall and then with wire nuts to the wires coming from inside the wall.
While this type of installation is easiest since it does not involve opening up walls it is considered to be inferior to installing the thermostat on the wall.
You should be able to bypass the unit thermostat and utilize the wall mounted thermostat only.
Thomas with cadet tech support shows you how to install a double pole wall thermostat on a 240 volt electric baseboard heater.
Using a wire connector connect the hot supply wire to the thermostat wires.
Check out our voltage blog pos.
Double pole 22 amp 120 volt 240 volt wall mount mechanical non programmable thermostat in white designed to replace most wall mounted line voltage thermostats 4 wire thermostat with color coded wires for easy installation.
Then remove the thermostat from the wall.
Typically this is marked l1 or line step 8.