How to Install a 240-Volt Electric Baseboard Heater

  • 01 of 04

    Electric Baseboard Heater Basics

    Electric baseboard heaters can provide confortable radiant heat

    Electric baseboard heaters provide a form of radiant heat, which uses natural air convection (hot air rises, cold air drops) to circulate heat into a room. Baseboard heaters are controlled by a wall thermostat or a built-in thermostat on the heater unit. Heaters come in two types: 120-volt or 240-volt. Electricians generally recommend 240-volt because it uses lower amperage and is more energy-efficient than 120-volt. Adding a 240-volt baseboard heater usually requires a new 20- or 30-amp double-pole circuit breaker and new circuit wiring to supply one or more heater units. This would be a dedicated circuit that is used only for the heater(s) and not other 240-volt appliances.

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  • 02 of 04

    Choosing a Heater Location

    Close up of baseboard heater
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    Baseboard heaters commonly are located under or near windows to combat the coldness of the glass. Heaters work most effectively if placed directly beneath a window to offset the heat loss through the window. Heaters cannot be located beneath an existing wall outlet, and they require a minimum of 1 inch of air space under the unit for the convective airflow to work properly. They also should have at least 12 inches of clearance from window coverings and furniture. Thermostats for baseboard heaters can go anywhere in the room but tend to give the most accurate reading when located on an interior wall and away from heat sources.

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  • 03 of 04

    Adding a Baseboard Heater Circuit

    Electrician working on wired electrical board
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    Unless you're adding a heater to an existing 240-volt heater circuit, you will need to have an electrician install a 240-volt, double-pole circuit breaker, and circuit cabling. Depending on the total wattage of the heater(s) you're adding, you may need a 20-amp or 30-amp circuit. A 20-amp circuit can safely power 3,800 watts of heating demand, while a 30-amp circuit is suitable for up to 5,700 watts. The standard circuit cabling for 20-amp circuits is 12-gauge (or 12 AWG) cable; 30-amp circuits need 10-gauge (10 AWG) cable. The circuit cable typically has two hot wires and a ground wire.

    If you will control the baseboard heater from a wall thermostat, you will also need a 240-volt "line voltage" thermostat installed.

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  • 04 of 04

    Installing an Electric Baseboard Heater

    electrical baseboard heater installation

    Once the circuit breaker and cabling is installed, the basic steps of installing a baseboard heater unit are relatively standard: 

    1. Make sure the circuit breaker is off and there is no voltage in the circuit wiring. 
    2. Remove the knockout on the back of the heater's connector box and install a 1/2-inch cable clamp to the box.
    3. Run the 240-volt circuit cable through the cable clamp opening, leaving 6 to 8 inches of extra cable extending beyond the clamp.
    4. Strip 1/2 inch of insulation from the end of cable wire, then tighten cable clamp onto the cable.
    5. Use a stud finder to locate walls studs behind the baseboard heater. Fasten the heater to at least two wall studs, using 1 1/2-inch drywall screws. Use a torpedo level to level the unit if it is a type that is not floor-mounted. (Note: If you have a floor-mounted unit, you may have to cut the baseboard where the heater goes in to fit the unit against the wall.)
    6. Look in the connection box for the factory wiring connection on the unit's heating element. Following the manufacturer instructions, cut the factory power wire connection or disconnect the wire connector (wire nut) that holds the connection together.
    7. Connect one factory wire to a hot power wire from the 240-volt circuit cable, and connect and the other factory wire to the second hot power wire from the 240-volt circuit cable. Secure the connections with wire connectors. 
    8. Install the connection box cover.
    9. Turn the power on at the circuit breaker and test the heater for proper operation.