It depends a little on the Thermostat it self. Some 220V thermostats only break one pole, others will break 2 poles. If there is only 2 wires (or terminals) it is a single pole thermostat. For this style, you will only interrupt one of the 2 hot wires and the other line goes directly to the unit. If there are 4 wires it will break both lines. This style is my preference because it completely disconnects power to the heater if the thermostat is OFF. Some 2 pole thermostats can vary in style, so Ask with more information if it is not obvious. Connect the 2 hot wires from power to what should be marked as the LINE side of the thermostat and connect the wires going to the heater to what should be marked as the LOAD side. If it is an older, unmarked thermostat, you may need to test it with a continuity tester to be sure that you do not create a short to the circuit. You should never be able to have continuity between the two hot wires on a four wire thermostat.
IF THE HEATER IS IN FACT 110V YOU ONLY USE THE L1 T1. The L1 is the black power in and the T1 is the black out to the heater. Sometimes the heater has a primary and secondary stage. To warm it up before it operates. I need to know if there are two black or a black and a red headed to the heater.
On a double pole thermostat L1 and L2 are red one of the black wires says off and the other black says cycle how do we hook it up
There are two black wires in box