Installing Electric Heaters

Intro

Adding an electric baseboard or wall heater can be a cost-effective way to bring heat to a cold spot or an area that gets only occasional use.

Plan 10 watts of heater capacity per square foot of room area. Check local codes for circuit requirements; some municipalities require a dedicated circuit protected by a 20-amp double breaker. In some cases, you can add heaters to existing 120-volt circuits. Confirm that the circuit voltage matches the heater voltage.

Place heaters on outside walls below windows. Never locate a heater beneath a receptacle. Follow the manufacturer's recommendations for placing furniture and draperies near the unit. In general, baseboard units are best for supplemental heat; blower-heaters are best for intense heat of short duration.

Prestart Checklist

Time
About 3 hours to run cable and install a baseboard heater and thermostat; about 2-1/2 hours to run cable and install a blower-heater

Tools
Voltage tester, drill, 1/2-inch bit, drywall saw, fish tape, screwdriver, stripper, long-nose pliers, lineman's pliers

Skills
Cutting into walls; stripping, splicing, and connecting wires to terminals; installing boxes; running cable into boxes

Materials
Heater, box for thermostat, 12/2 cable, electrician's tape, wire nuts

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Step 1

Cut an opening for a large-capacity remodel box. Run 12/2 cable to the location of the thermostat. Do not connect the cable to its power source. Run cable from the opening to the heater location. Strip cables and clamp them into the box. Install the box.

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Step 2

No junction box is required for the cable running to the heater -- the box is built into the unit. Strip the incoming wires. (You also can run the feeder line directly to the heater and then to the thermostat. Check the manufacturer's instructions.)

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Step 3

Place the heater face down on the floor and remove the cover/cable clamp. Attach the house ground line to the green screw on the heater. Using wire nuts, connect incoming lines to the heater leads. Close and fasten the cover/clamp.

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Step 4

Locate and mark wall studs. Push the cable into the wall. Attach the unit with at least two 1-1/2-inch drywall screws. Tighten, then back off a half turn to allow for the expansion and contraction of the metal housing when the unit is turned on and off.

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Step 5

Wire the thermostat, using wire nuts and electrician's tape. Install the thermostat and snap on its cover. Connect to the power source or new circuit and test the unit.

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Installing a blower-heater

A blower-heater unit fits between wall studs and is somewhat simpler to wire because it has a self-contained thermostat. Many units run on 240 volts. Check local codes for requirements.

A blower-heater must be a safe distance from nearby walls and furnishings. When choosing a location for the heater, maintain 12 inches from any adjacent walls. For safe and effective operation, locate the box 12 inches above the floor and keep the area 3 feet in front of the box clear. Check the manufacturer's recommendations before locating the unit.

Before cutting an opening for the unit, drill a finder hole and use a wire to check that the wall cavity is clear of pipes and wires. Use a drywall saw to cut the opening. Run the recommended cable to the opening.

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Step 1

Remove one of the knockouts in the housing. Insert a clamp and pull 10 inches of cable into the box. Clamp the cable and fasten the housing in place with 1-inch (longer if needed) drywall screws. Strip incoming wires.

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Step 2

Attach the incoming wires to the heater leads. Fasten the heater unit into the housing, being careful that the wires do not get caught between the motor and the housing. Attach the grille and thermostat knob. Connect to the power source.

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