035-17477-001 Rev. A (801)
18
Unitary Products Group
6.
All joints must be made to provide a permanent, air-tight,
water-tight seal.
7.
Support the combustion air and vent piping such that it is
angled 1/4” per linear foot so that condensate will flow
back toward the furnace. Piping should be supported
with pipe hangers to prevent sagging. Maximum spacing
between hangers is five (5) feet, except SDR-PVC pip-
ing, where maximum spacing is three (3) feet.
8.
Seal around the openings where the combustion air and
vent piping pass through the roof of side wall.
NOTE:
Vent pipe must be sloped 1/4” per foot to allow con-
densate to flow back to the furnace.
METHOD TWO: ONE PIPE SYSTEM
This type installation will use combustion air from within the
space surrounding the furnace. This may be from within the
space in a non-confined location or it may be brought into the
furnace area from outdoors. It is not directly ducted into the
furnace. A single, properly sized pipe from the furnace vent
connector to the outdoors must be provided.
For upflow models combustion air is brought into the furnace
through the unit top panel opening. Do not install a pipe into
the intake collar on top of the burner box. Figure 24 .
For downflow/horizontal models, remove a minimum of two
gas piping knockouts for combustion air access. Do not
install a pipe into the intake collar on bottom of the burner
box. For details, refer to Figure 25.
COMBUSTION AIR
All installations must comply with Section 5.3, Air for Com-
bustion and Ventilation of the National Fuel Gas Code, ANSI
Z223.1 or Sections 7.2, 7.3 or 7.4 of CAN/CGA B149.1 or .2
Installation Code - latest editions.
An unconfined space
is not less than 50 cubic feet per 1000
Btu/hr input rating for all appliances installed in that area.
Rooms communicating directly with the space containing the
appliances are considered part of the unconfined space, if
openings are not furnished with doors.
A confined space
is an area with less than 50 cubic feet per
1000 Btu/hr input rating for all appliances installed in that
area.
The following must be considered to obtain proper air for
combustion and ventilation in confined spaces.
Solvent cements are flammable and must be used
in well-ventilated areas only. Keep them away from
heat, sparks and open flames (including pilots). Do
not breathe vapors and avoid contact with skin and
eyes.
Vent piping must be insulated with 1/2” Armaflex
insulation if it will be subjected to freezing temper-
atures such as routing through unheated areas or
through an unused chimney.
When combustion air pipe is installed above a sus-
pended ceiling, the pipe must be insulated with 1/
2” Armaflex type insulation. The combustion air
pipe should also be insulated when it passes
through a warm, humid space.
FIGURE 24 :
Vent Pipe Connection - Upflow
FIGURE 25 :
Vent Pipe Connection -
Downflow/Horizontal
VENT PIPE CEMENTS
INTO SOCKET JUST
UNDER TOP PANEL
COMBUSTION AIR
COMBUSTION AIR
GAS PIPING
KNOCKOUTS
VENT PIPE PASSES
THROUGH TOP PANEL
