Installing natural gas garage heaters, no matter what brand or type you have, involves the same three basic steps.
Step 1 - Mount the Heater
The mounting height of the heater should be 18 inches above the floor and mounted by a hanging bracket. Put the vent outlet, gas, and electrical connections, to the right or left of the fan. The fan should direct air towards the areas of maximum heat loss. It should not interfere with the proper circulation of air in the garage.
Step 2 - Pipe Size and Pipe Installation
Size the gas pipe by referring to the instruction manual for your gas heater in order to provide adequate gas pressure to the heater. Use proper joint compounds for making pipe connections and test for leaks before operating the heater. Install the gas piping according to applicable local codes. Adequately support the piping for the heater. It will likely have to pass inspection before you can operate it in some municipalities. Call your local gas company for further information.
Step 3 - Make the Electrical Connections and Venting
Mount the thermostat five feet above the floor on a vertical, vibration-free surface. Keep it in an area where it is exposed to the average temperature air. Refer to the wiring diagram in the installation manual for setting up all wiring connections.
The unit heater must be vented and comply with all local building codes. The ventilation should allow for the maximum combustion of the gas and proper venting.