How to Install & Wire Your Electric Garage Heater

We use our garage in a variety of ways. It can be used for storage, a place to work out or simply have some alone time. Keep your garage space warm this winter with an electric garage heater.

This heater is easy to install. In fact, it's so easy you can do it yourself. By following a few simple instructions you can safely install this heating method in short time.  

Below is a do-it-yourself guide designed to help simplify the process. Also included are tips for choosing the right garage heater, wiring your thermostat, and easy ways to get the most out of your garage heater.

Enjoy warm comfort all year long. An electric garage heater is a great way to do it!  

• Before You Start
• What You'll Need
• How to Wire an Electric Garage Heater
• Tips, Warnings and Additional Information

Before you purchase your new garage heater, take a few minutes to measure the space you are planning to heat. You'll want to make sure you get a garage heater that will warm the space effectively. Electric garage heaters are powered by watts following the equation below so you can ensure yourself the perfect heater for the coverage you need:

Square Feet x 10 = Number of Watts required

The chart below exemplifies watts and square footage. Following this handy guide will ensure great results:

It's important to remember that the square footage listed in the chart above is a general guideline for determining your garage heater you need. There can be a lot of variation because of insulation, drafts and other external factors that might play a role in how effective the heater is.

If you aren't sure how much power your garage heater requires, check with your local heating contractor to get a better idea of the capacity you need.

1. Run the sheathed cable from your circuit breaker to your thermostat location.   
2. Run the remaining cable from the thermostat location to the location where your garage heater will hang
3. Install the junction box at the location where your heater will hang with two screws
4. Support the sheathed cable with the cable straps

Helpful Hint: It's best if you space the cable straps approximately 4 feet apart with cable straps approximately 12" from the junction box, thermostat and panel.

5. Turn off the main circuit breaker and remove the panel cover.
6. Install the double circuit breaker on to the bus bars.

Helpful Hint: Most circuit breakers have slots, which catch tabs and the breaker clicks down onto the bus bars once you hook the tabs on.

6. Remove the cable sheathing from inside the panel box.
7. Remove 1" of insulation from two of the wires.
8. Connect the bare ground wire to the ground bus wire, which go on the breaker terminal lugs.
9. Safety Tip: Use extreme caution during this step. Although the power is off, the main breaker terminal lugs are still live. Never touch the main breaker terminal lugs.

Helpful Hint: Be sure to thoroughly tighten the lug screws for best results and safety.

10. Color the wires so that they meet local codes and ordinances.
11. Replace the panel cover.

1. Remove 6" of sheathing from both cable ends at the thermostat.
2. Remove 1" of wire from the ends of the wires.
3. Color the wires so that they meet local codes and ordinances.
4. Attach the two wires that lead to the circuit breaker panel to the wires marked Line or L1 and L2.
5. Attach the wires that lead to the heater to the wires labeled Load or T1 and T2.
6. Cap each of the connections with wire nuts.
7. Twist the bare ground wires the bare ground wires together and attach them to the thermostat's green ground wire.
8. Mount the thermostat to the wall.

Helpful Hint: Be sure to keep the wire connections inside the thermostat enclosure.

1. Attach the flexible metal conduit to a knockout hole in the junction box using an FMC connector.
2. Attach the other end of the flexible metal conduit to the junction box of the heater using a second FMC connector
3. Remove 6" of sheathing from the end of the cable at the heater.
4. Put the cable in the junction box.
5. Run two pieces of the 10 AWG black insulated wire and 1 piece of the 10 AWG green insulated wire through the conduit.

Helpful Hint: There should be a minimum of 6" of insulated wire extending into both junction boxes.

6. Strip 1" of wire from all 5 wires in the ceiling junction box.
7. Twist the black wires together and cap with a wire nut.
8. Color all wires so that they meet all codes and local ordinances.
9. Twist the recoded wire and the remaining black wire. Cap with a wire nut.
10. Ground the metal junction box. Twist the two ground wires together and attach them to the box with a screw.
11. Put the cover on the box.
12. Remove 1" of insulation from the three wires in the heater junction box.
13. Connect each black heater wire to a black supply wire.
14. Connect the two green ground wires together.
15. Cap all connections with wire nuts.
16. Replace the heater junction box and cover securely.
17. Follow manufacturer's instructions for installing your new garage heater.

• Be sure to check with your state and local ordinances to make sure the garage heater installation is up to code.
• Always follow manufacturer's instructions when installing your new electric garage heater.
• Be sure to contact an electrician if you are uncomfortable with installing your new electric garage heater yourself.
• If possible, insulate your garage. It will keep you cooler during the summer and warmer during the winter. Plus, it will save you money and make your garage heater more efficient.
• If your space is too large to heat with just one electric garage heater, consider purchasing two. Then, when you install the garage heaters, place them strategically in the space you are trying to heat. By using this method, you'll have plenty of room to work and will be able to enjoy cozy warmth provided by your electric garage heaters.