Do-It-Yourself Electric Baseboard

Shut off the main power switch inside the electrical breaker box. The main switch will be clearly marked on the panel, and may be a larger switch seated above the other breaker switches. Remove the screws around the breaker panel cover and take it off the front of the panel.

Drill a 5/8-inch hole through the baseboard trim at the location of the thermostat and each of the baseboard heaters. Ensure that there are no receptacles or light switches above your holes and heater locations.

Secure 12/2 electrical cable to a fish tape with electrical tape. Push the cable into the hole for the thermostat and run it through the attic and down to the electrical breaker box. Feed another cable on a fish tape through the thermostat hole and down to the first heater location. Feed another cable up from there and down to the next heater. Run cable to all baseboard heaters in succession, stopping at the last one.

Cut 12 inches lengthwise down the ends of all cable jackets with a utility knife. Cut off the loose jacket. Strip 3/4 inch of insulation off the ends of all black and white wire ends with wire cutters.

Wrap the black from the cable at the breaker panel around the terminal screw on a 15 amp double breaker switch and the white wire around the other. Tighten both terminal screws with a screwdriver firmly. Loosen a terminal on the ground bus holding all the bare copper and green wires and put the copper wire from your cable into it. Tighten that terminal screw firmly. Press the un-wired end of the breaker onto the inside edge of the hot bus holding the breaker switches and clip the wired side on the outside edge.

Wrap the black and white wires from the cable that runs from the breaker panel to the thermostat around the terminals on the line side of the thermostat and tighten. Wrap the wires from the cable running to the first heater around the load side terminals on the thermostat and tighten both screws securely. All terminals will be clearly marked.

Cut a 6-inch length of bare copper wire and twist one end of it around the copper ground wires from both cables. Cap the twist with a wire nut by twisting it over the wires clockwise. Wrap the other end of the 6-inch copper wire around the ground terminal inside the thermostat.

Connect the black wires from both cables at the first heater to the black heater wire by twisting the three together and top them with a wire nut. Twist the white wires from your cables around the other heater wire and cover with a wire nut. Both heater wires are hot wires, so it doesn't matter which one gets the black wires and which gets the white. Connect the ground wires together with another 6-inch length and cap with a wire nut. Connect the other end of the short length to the ground terminal in the heater.

Connect all consecutive heater units in the baseboard heating system to the cables as in step 8 until the last unit. Connect the black wires from the incoming cable to the heater wires and the copper wire to the ground terminal by themselves on the last heater.

Screw the mounting screws into the baseboards through the backs of the heater systems and tighten moderately. Place the covers over the outsides of the heater units.

Remove the two knockouts on the breaker panel cover over your new breaker switch with pliers. Replace the cover on the breaker panel and restore the power by flipping the main switch to the on position. Set the thermostat for a temperature higher than the room temperature to test the electric baseboard.