How to hang a garage heater

How you hang a garage heater depends on what kind it is, and each kind has a different set of rules. Read the manual for the specific model before you buy a bracket or drill a hole, because the maker's mounting height, clearance and fastener instructions are part of the product's listing and its warranty.

• Hard-wired electric ceiling heater. A box with a heating element and a fan, fixed to the ceiling or high on a wall. The Comfort Zone 7,500 W ceiling-mount heater is one. It needs a dedicated 240V circuit and a hard-wired connection, which is electrician's work.
• 240V electric heater with a plug. The InoKraft 7,500 W with a NEMA 14-50 plug and the Dura Heat 3,750 W mount on a bracket and plug into a receptacle. The receptacle is the circuit work; the hanging is mechanical.
• Gas or propane unit heater. The Mr. Heater 50,000 BTU and 80,000 BTU hang from the ceiling on rods or brackets, with a gas line and a vent to the outside. This is the one that needs a licensed gas fitter, a permit in most places and careful attention to clearances and combustion air.
• Portable radiant heaters. The Buddy and the DAHTEC 1500W sit on the floor or a stand. Nothing to hang.

If you are still choosing, start with is a garage heater worth it and the best garage workshop heater, then size the heater with the heater calculator.

Location decides whether the heater warms you or only the ceiling. The usual considerations:

• Throw direction. Hang the heater high on the wall opposite the area you want warm, or near the center of the ceiling, so the fan pushes air across the work zone. Do not point it at a car's windshield from a few feet away, or at a shelf of flammable supplies.
• Away from dust. A heater directly above a table saw collects sawdust, which burns. Place it away from the dusty machines, or in a zone the collector and the air filter keep clean. Check the layout on the layout page for your bay.
• Away from the garage door. Overhead doors and their tracks move; the heater must stay clear of the door's travel, the opener rail and the spring. Measure with the door open.
• Close to the power or the gas. A shorter run is cheaper and easier. For a plug-in unit, put the receptacle where the cord reaches without tension.
• High enough. Hot air rises, and a ceiling-mounted heater with a downward fan covers more floor from height. The maker states a minimum and maximum mounting height. Many codes also require fuel-burning heaters in a garage to have the burner raised above the floor; ask your building department.
• Not above or near fuel. Keep gasoline, solvents, paint and aerosol cans well away. The manual lists the clearance to combustibles on each side, top and bottom.

In a 22 x 22 ft garage (484 sq ft), a single 4.5 kW heater (about 15,500 BTU per hour with typical insulation) placed near the center of a wall, 8 to 10 ft from the work area, covers the room; a 32 x 24 ft garage needing about 24,500 BTU may be better with two units than one large one, so that no corner is cold. These are planning figures, not a heating design.

Never hang a heater from drywall or a ceiling panel alone. Find the joists or trusses and fasten to them. Use a stud finder, then confirm by probing with a small drill bit. Ceiling joists in a garage are commonly spaced 16 or 24 in on center. Mark the center line of each joist. Open the box and read the maker's template and weight. Check that the structure can take it: a trussed ceiling with a bottom chord rated for light loads may not take a heavy unit, and the manufacturer of the truss, a builder or an engineer is the person who can say so.

If the heater sits between joists, add blocking, a 2 x 6 or 2 x 8 laid flat or on edge between two joists, fastened with structural screws, to carry the bracket. For a wall mount, go into studs with lag screws; for a masonry wall, use anchors rated for the load. The maker's manual gives the hardware sizes. Do not substitute drywall anchors or toggle bolts for a heater that vibrates and weighs more than a light.

Gas unit heaters often hang on threaded rod or chain from the structure with the bracket the maker supplies. The hanging hardware must carry the unit and must not conduct heat to combustibles. Follow the manual.

1. Mark and drill. Hold the bracket against the ceiling or wall at the chosen spot, level it, mark the fastener holes over the framing and drill pilot holes.
2. Fasten the bracket with the lag screws or structural screws the manual specifies, into framing. Tighten firmly but do not crush the wood. Check that the bracket does not move.
3. Lift the heater with a second person or a lift. Heaters are awkward and heavier than they look. The listing gives the weight; do not guess. Support it while you attach it.
4. Attach the heater to the bracket with the supplied hardware and set the louver direction. Level it as the manual requires.
5. Check clearances from the heater to combustibles, to the ceiling, to the wall, to the car and to anything stored below, against the manual's table.
6. Do not connect power or gas yet. The mechanical part is done; the connection comes next.

Use a stable ladder or a scaffold, wear safety glasses while drilling overhead and keep dust out of your eyes. If the garage is full, clear the floor below the work area.

This step is the one to leave to a licensed professional where the law or your insurance requires it, and in many places it is required.

Electric heaters

An electric heater is a continuous load, so the conductor and breaker are sized at 125 percent of its running current. In the site's tables: a 3,750 W heater at 240V draws 15.6 A, which gives a 20 A breaker and 12 AWG copper; a 4,500 W unit draws 18.8 A, a 25 A breaker and 10 AWG; a 5,500 W unit 22.9 A, a 30 A breaker and 10 AWG; and a 7,500 W unit draws 31.3 A, a 40 A breaker and 8 AWG copper (NEC Table 310.16, 60 C column, 8 AWG at 40 A). A plug-in unit takes a matching receptacle, and a 14-50 is a 50 A device: the Leviton 14-50 receptacle is the usual part, on a circuit whose breaker and wire the electrician matches to the heater's nameplate and the plug's rating. Do not share the circuit with the car charger or a motor. A hard-wired unit connects in a junction box with a disconnect where the code requires. The 240V circuit calculator, how to install a 240V outlet and the cost guide cover the circuit.

Gas and propane unit heaters

A gas unit heater needs a gas supply sized for its input, a shut-off valve and a sediment trap, a vent to the outside, a source of combustion air, and clearances to combustibles. Many codes also address garage installations specifically, including how high the burner must sit and how the heater is protected from vehicles. A licensed gas fitter pulls the permit and tests the line for leaks. Add a carbon monoxide alarm. Do not vent a gas heater into the garage, and do not reuse a vent from another appliance without checking.

Thermostat

Mount the thermostat on an interior wall at working height, away from the heater's airflow and from the door, so it reads the room, not a draft. A low-voltage or line-voltage thermostat is part of the heater's wiring: follow the manual. Set it low when you are away and raise it while you work; the loss scales with the temperature difference.

1. Turn on the circuit and run the heater on low, then high. Listen for unusual noise and check that the louvers move freely.
2. Check for heat patterns and smells. A new element smells a little; a burning smell that persists is a stop.
3. Feel the bracket and the fasteners for movement after the first hour.
4. Measure the room temperature in the work zone with a thermometer over an hour; adjust the louvers.
5. Label the breaker and the disconnect.
6. Test the smoke and carbon monoxide alarms and put a fire extinguisher near the exit.
7. Vacuum the intake and the housing periodically. In a woodshop, dust on a hot element is a fire hazard.

Run the heater during the evening before your first big project, not on the day. Heat soaks into the slab and the walls slowly, which is why a cold garage takes hours to feel warm.

• Hanging from drywall. It will pull out. Use the framing.
• Ignoring the clearances. The manual's distances to combustibles, the garage door and the car are mandatory.
• Installing over a table saw or a sander. Sawdust burns.
• Oversizing. A heater that is too big short-cycles, is noisy and costs more to wire. Size to the load, then add 10 to 20 percent only if you must.
• Skipping insulation. A heater will run forever in a leaky box. The door kit (two-car or one-car) comes first.
• A DIY connection to the panel or the gas line. These are the hazards.
• Forgetting the permit. Insurance claims can turn on it.

For the whole picture of heating a shop, including the cooling side, see how to build a workshop in a garage and the mini-split calculator.