You either have a new line voltage thermostat or have to replace your old line voltage thermostat. In either case the process is much the same.
- Make sure that all power is turned off at the breaker panel. Most heaters that use a line voltage thermostat usually use 240v current so the breaker will either be a double pole breaker or you will need to turn off two single pole breakers to kill all of the power.
- Check to see which wires are hooked to the breakers. In most cases it will be the red and black wires, but I have seen many times that the white and black wires were used. Often there is no red available when the white is used.
- Take out the two screws that hold the thermostat to the junction box. When you get the thermostat out make a note of which wires go to the heater (load) and which wires are coming from the breakers. (line)
- If you have a single pole thermostat installed one of the sets of wires may be wired straight through the box or have the line and load wires connected directly in the box. With a double pole t-stat you will have both sets of wires running through the t-stat.
- Remove the old thermostat and wire the new t-stat in the circuit with the load wires hooked to the load or heater and the line wires hooked to the wires coming from the breaker. Make sure to get a very good tight connection as resistance loads will heat up quickly if good contact is not made. This poor connection can and will start fires.
- Turn the power on and check the heater for heat output.
- Turn the power back off and carefully screw the thermostat to the junction box securely. Then you can reapply the power to the circuit.
Now you are up and running with a new line voltage thermostat installed. http://www.fixya.com/support/r3894275-manual_honeywell_find_honeywell_manuals