Carrier AERO 39MN Installation, Start-Up And Service Instructions Manual page 115

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 ensure
that any condensate that occurs in the vent duct drains away
from the combustion blower fan housing. The duct opening
should be protected by a 1 / in. x
2
screen. An optional rainhood may be used over the discharge
opening to prevent wind-driven rain from entering the vent duct,
but should not intersect the flue gas discharge path. See Fig. 97.
IMPORTANT: Outdoor units must be individually vented
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 vent-
ing of the heating units is the installer's responsibility. Vent pip-
ing is supplied by others. When operated with the venting
system in place, proper duct furnace operation must be verified,
including flue gas analysis of each connected furnace.
VENT HOOD
1 / in. (12 mm x 12 mm) mesh
2
AHU
CABINET
Fig. 97 — Outdoor Horizontal Venting
Use single wall or double wall (Type B) vent pipe of diame-
ters listed below.
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 mini-
mum 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 (3m). Horizontal runs
should be pitched upward
supported at 3 ft (1m) 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 condensa-
tion inside vent pipe. Insulation should be a minimum of
(12.7 mm) thick, foil-faced material suitable for temperatures 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. 98.
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
114
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 should be
4
AHU
CABINET
a39-4395
1 / in.
2
COMB.
BLWR.