035-14370-000
650.75-N4U
Unitary Products Group
19
Note:Vent pipe must be sloped 1/4” per foot to allow conden-
sate 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. It is not necessary to
install a pipe into the intake collar on top of the burner box.
Refer to Figure 23 .
For downflow/horizontal models combustion air is brought
into the furnace through the unit side panel openings.
For downflow/horizontal models, remove a minimum of two
gas piping knockouts for combustion air access. It is not nec-
essary to install a pipe into the intake collar on bottom of the
burner box. For details, refer to Figure 24.
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.
Air Source from Inside the Building - Two permanent
openings, one within 12 inches of the top of the confined
space and one within 12 inches of the bottom, shall each
have a free area of not less than one square inch per 1,000
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 23 : UPFLOW VENT PIPE CONNECTION
(P*UR / FG9-UP / G9T-UP)
M
P
C
1
3
2
O
FF
O
N
COMBUSTION AIR
VENT PIPE
CEMENTS
INTO SOCKET JUST
UNDER TOP PANEL
FIGURE 24 : DOWNFLOW / HORIZONTAL VENT
PIPE CONNECTION (P*DH/ FG9-DH /
G9T-DH)
Y
W
R
G
C
C O O L
H E A T
P A R K
P A R K
L I N E
X F M R
E A C
H U M
C I R
L I N E
X F M R
E A C
H U M
V E N T P I P E P A S S E S
T H R O U G H T O P P A N E L
C O M B U S T I O N A I R
G A S P I P I N G
K N O C K O U T S
