Gas-Fired Products 100 User Manual

 

 Form 

#43343530 

 

–38– 

JJuly 08

 

17.0) 

AIR FOR COMBUSTION 

 

If indoor combustion air is to be supplied for a tightly enclosed area, one square inch of free area opening shall be 
provided below the heater for each 1,000 Btu/hr of heater input.  Adequate clearances around the air inlet screen 
must be maintained at all times.  In larger open areas of buildings, infiltration normally is adequate to provide air for 
combustion. 

 

17.1) 

DIRECT OUTSIDE AIR FOR COMBUSTION 

 

Outside combustion air should be supplied directly to the heater when the building is subject to negative pressure, or 
when contaminants or high humidity are present in the building air.  These contaminants include paints, solvents, 
corrosive vapors or any other foreign particles that may cause damage to the heater or result in poor combustion. 

 

Outside combustion air can be brought directly to the heater by a 4” diameter duct less than 50 ft. long or equivalent 
(see table in Section 16).  This is attached to the 4” diameter starting collar (supplied with heater).  The starting collar 
is fitted to the rear of the burner box cabinet as shown below.  An approved vent cap must be placed directly on the 
end of the outside combustion air inlet pipe.  The combustion air inlet should be not less than 3 ft. (0.9m), either 
vertically or horizontally, from the flue vent termination.  The air intake terminal must be located not less than 1 ft. 
(30cm) above grade.  It is good installation practice to supply combustion air from the same pressure zone as the 
vent outlet.  Avoid bringing combustion air to the heater from an attic space.  There is no guarantee that adequate 
combustion air will be supplied. 

 

If the heater is installed less than 2 ft. from the ceiling, a combustion air inlet kit PN 44129510 must be provided to 
allow for expansion/contraction of straight tube heaters (PTS series). 

 

In colder climates, where necessary, insulate the outside combustion air duct.  In high humidity applications, the 
burner box should be sealed with silicone sealer.

 

Combustion Air Cap

(Leslie VersaCap

Type B)

4” Diameter

Single-Wall Pipe

Flashing

1/4” (6mm)

per ft. slope downwards

towards vent terminal

6” (15cm)

Minimum

4” Starting Collar

Burner Box

(side view)

3 ft. (91cm)

Minimum

4” Flexible Air Inlet Hose

2 Ft. Long

4” Spring

Tension Clamp (2 each)