HTP EL-399NVWH - Manual (Page 40)

40
LP- 346 REV. 3.20.14
M. INDOOR COMBUSTION AIR INSTALLATION IN
CONFINED OR UNCONFINED SPACE
NOTE: This installation is intended for commercial applications.
For residential applications, it is recommended to pipe intake
combustion air from the outdoors.
This heater requires fresh, uncontaminated air for safe operation
and must be installed in a mechanical room where there is
adequate combustion and ventilating air. NOTE: To prevent
combustion air contamination, see Table 3.
Combustion air from the indoor space can be used if the space
has adequate area or when air is provided through a duct or
louver to supply sufficient combustion air based on the heater
input. Never obstruct the supply of combustion air to the
heater. If the heater is installed in areas where indoor air is
contaminated (see Table 3) it is imperative that the heater be
installed as direct vent so that all combustion air is taken directly
from the outdoors into the heater intake connection.
Unconfined space is space with volume not less than 50 cubic
feet per 1,000 Btu/hour (4.8 cubic meters per kW) of the total
input rating of all fuel-burning heaters installed in that space.
Rooms connected directly to this space, through openings not
furnished with doors, are considered part of the space.
Confined space is space with volume less than 50 cubic feet per
1,000 Btu/hour (4.8 cubic meters per kW) of the total input rating
of all fuel-burning heaters installed in that space. Rooms
connected directly to this space, through openings not furnished
with doors, are considered part of the space.
When drawing combustion air from inside a conventionally
constructed building to a confined space located on the same
story, such space should be provided with two permanent
openings: one located 6” (15 cm) below the space ceiling, the other 6” (15cm) above the space floor. Each opening should have a free
area of one square inch per 1,000 Btu/hr (22cm
2 /kW) of the total input of all heaters in the space, but not less than 100 square inches
(645cm 2 ).
When drawing combustion air from inside a conventionally constructed building to a confined space located on different stories, such
spaces should be considered as communicating spaces when connected with one or more permanent openings in doors or floors
having a total minimum free area of two square inches per 1,000 Btu/hr (22cm
2
/kW) of the total input of all heaters in the space, but not
less than 200 square inches (645cm
2
).
If the confined space is within a building of tight construction, air for combustion must be obtained from the outdoors as outlined in the
Venting section of this manual.
NOTE: It is always recommended to isolate the heater installation room from the rest of the building and bring uncontaminated air in
from the outside for combustion and ventilation.
Figure 20 – LP-387-Z