2. Install a 4" air supply pipe from the intake terminal to the air intake boot on the burner. Galvanized pipe (4") or flexible 4" metal piping can be used. Use minimum number of elbows and keep the total pipe length to a minimum. Properly support pipe sections every 4 feet with a hanger or bracket. The installation must comply with all local codes and authorities having jurisdiction. Note: In climates where the outside air temperature drops below -20 Fit is recommended to have a minimum of 6 to 8 ft of 4” diameter metal pipe in conditioned (warm) space to prevent cold combustion air from causing fuel gelling problems. A vacuum relief breaker on the air intake side can also be used to draw in some conditioned combustion air.