Step 1.  Make sure you have turned off all electrical power at the circuit breaker, or fuse box (Lock or tag the panel door to insure no one turns on the power while you are installing the thermostat).

Caution: Failure to turn off all electrical power can cause serious electrical shock, burns, or death

Step 2.  Remove one of the junction box covers at the end you wish to wire.

Step 3.  Disconnect only one factory connector on the side you have open, leaving two loose heater wires.

Step 4.  Connect the supply grounding wire to the green grounding screw, if you have not already done so.

Step 5.  If not already present, route supply wire from the circuit breaker to the thermostat wiring box, and from the thermostat wiring box, to the heater, for later use.

Step 6.  In the thermostat wiring box, connect the ground wire coming from the circuit breaker to the ground wire leading to the heater. Make sure to connect the ground to the thermostat or wiring box, if available.

Stop

(The next steps will differ depending on which thermostat you are installing)

Step 7.  Using a wire connector, connect the hot supply wire to the thermostat wires. Typically, this is marked “L1” or “Line.”

Step 8.  Connect the remaining thermostat wire, typically marked "T1" or “Load,” to the same color supply wire feeding the baseboard heater.

Step 9.  Connect the white supply wire coming from the circuit breaker to the same color supply wire feeding to the baseboard heater.

Step 7.  Using wire connectors, connect a hot supply wire, which is typically black, to thermostat wire one (typically it is marked L1 or Line).

Step 8.  Connect the remaining supply wire, which is typically white, to the second thermostat wire (typically marked L2 or Line).

Step 9.  Connect one of the thermostat wires, typically marked “T1” or “Load” to the black wire leading to the heater.

Step 10. Connect the remaining thermostat wire, typically marked “T2” or “Load” to the remaining white wire leading to the heater.

Step 10/11.  Carefully tuck all wires into the wiring compartment, and mount the thermostat to the wall.

Step 12.  In the baseboard wiring junction box, connect each supply wire coming from the thermostat to each loose heater wire. Replace the junction box cover

Step 13.  Turn the power back on at the circuit breaker or fuse box.

Step 14.  After turning the power on, turn the thermostat knob fully clockwise. When the room reaches comfort level, turn the knob counter-clockwise until a slight click is heard.

Step 15.  The heater will now cycle around this pre-set temperature.