Air For Combustion; Direct Outside Air For Combustion - Space-Ray LTU SERIES Installation And Operation Instructions Manual

19.1)

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 perforated fresh air plate must be
maintained at all times. In larger open areas of buildings, infiltration normally is adequate to provide air for combustion.
19.2)

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 6" diameter duct less than 50 ft. long or equivalent. This
is attached to a 6" diameter starting collar. The starting collar is fitted to the top of the control cabinet after first removing
and discarding the perforated cover. An approved vent cap must be placed directly on the end of the outside combustion air
inlet pipe. The combustion air inlet should be a minimum of 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 flexible transition section (e.g., flexible aluminum duct) must be
provided to allow for expansion/contraction of straight tube heaters (LTS series).
In colder climates, where necessary, insulate the outside combustion air duct. Avoid locating the outside combustion air duct
directly above the control box. Provide a capped cleanout T as necessary. In high humidity applications, the control box
should be sealed with silicone sealer.
In multiple heater applications, the combustion air intake may be ducted individually or common ducted in the same
configuration as shown for venting in Section 19. For combustion air intake duct sizing, please refer to the Vent Sizing Table
and use the diameter indicated, based on the number of heaters per duct.
Form #43155260
Mar–05
VERTICAL
THROUGH THE ROOF
Horizontal
Through Sidewall
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