Carrier Aero 39MN Series Installation, Start-Up And Service Instructions Manual page 165

Venting for Outdoor Installations — The venting system is
designed for direct discharge of flue gases to the outdoors. The
vent discharge opening should be located to provide an unob-
structed discharge to the outside and should be located as far
from the combustion air inlet as possible but in the same pres-
sure zone.
The vent duct should pitch down toward the outlet, to en-
sure that any condensate that occurs in the vent duct drains
away from the combustion blower fan housing. The duct open-
ing should be protected by a
mesh screen. An optional rainhood may be used over the dis-
charge opening to prevent wind-driven rain from entering the
vent duct, but should not intersect the flue gas discharge path.
See Fig. 137.
IMPORTANT: Outdoor units must be individually vented.
Venting For Indoor Installations — All duct furnaces must
be connected to a venting system to convey flue gases outside
of the heated space. Vent systems must be sized and installed
in accordance with ANSI Z223.1 (NFPA 54) or in Canada
CAN/CGA - B149.
There are two methods for venting indoor furnace installa-
tions: vertical venting and horizontal venting.
Vertically Vented Duct Furnaces (Category I) — Proper
venting of the heating units is the installer's responsibility. Vent
piping is supplied by others. When operated with the venting
system in place, proper duct furnace operation must be veri-
fied, including flue gas analysis of each connected furnace.
Use single wall or double wall (Type B) vent pipe of diame-
ters listed below.
VENT HOOD
1 / in. x 1 / in. (12 mm x 12 mm)
2 2
AHU
CABINET
Fig. 137 — Outdoor Horizontal Venting
INPUT RATING
(BTUH)
75,000 - 149,999
150,000 - 400,000
401,000 - 600,000
Maximize the height of the vertical run of vent pipe. A min-
imum of 5 ft (1.5 m) of vertical pipe is required. The top of the
vent pipe must extend at least 2 ft (0.61 m) above the highest
point on the roof. (Use Listed Type B vent for external runs.)
An approved weatherproof vent cap must be installed to the
vent termination.
Horizontal runs must not exceed 75% of the vertical height
of the vent pipe, up to a maximum of 10 ft (3 m). Horizontal
runs should be pitched upward
should be supported at 3 ft (1 m) maximum intervals.
Design vent pipe runs to minimize the use of elbows. Each
90-degree elbow is equivalent to 5 ft (1.5 m) of straight vent
pipe run.
Vent pipe should not be run through unheated spaces. If
such runs cannot be avoided, insulate vent pipe to prevent con-
densation inside vent pipe. Insulation should be a minimum of
1 / in. (12.7 mm) thick, foil-faced material suitable for tempera-
2
tures up to 500°F (260°C). Vent connectors serving Category 1
heaters must not be connected into any portion of a mechanical
draft system operating under positive pressure. See Fig. 138.
IMPORTANT: Dampers must not be used in vent pip-
ing runs. Spillage of flue gases into the occupied space
could result.
VENT HOOD
FLUE GAS FLOW
UNOBSTRUCTED
COMBUSTION
AIR INLET
LOUVER
COMBUSTION AIR OPENING
165
VENT PIPE
INPUT RATING (W)
DIAMETER
21,980 - 43,958 5 in. (126 mm)
43,960 - 117,228 6 in. (152 mm)
117,229 - 175,842 7 in. (178 mm)
1 / in. per ft (21 mm/m) and
4
AHU
CABINET
a39-4395
COMB.
BLWR.