Carrier AERO 39MN Installation, Start-Up And Service Instructions Manual page 116

NOTE: See the section Vertically
Vented Duct Furnaces on page 113
for vent pipe diameters.
Horizontally Vented Duct Furnaces (Category III) — Pres-
sures in Category III venting systems are positive and therefore
care must be taken to avoid flue products from entering the
heated space. Use only vent materials and components that are
UL listed and approved for Category III venting systems.
All vent pipe joints must be sealed to prevent leakage into the
heated space. Follow instructions provided with approved vent-
ing materials used. The proper vent pipe diameter must be used,
to ensure proper venting of combustion products. See the section
Vertically Vented Duct Furnaces on page 113 for vent pipe diam-
eters.
The total equivalent length of vent pipe must not exceed 50 ft
(15.25 m). Equivalent length is the total length of straight sec-
tions, plus 5 ft (1.52 m) for each 90 degree elbow and 2.5 ft
(0.76 m) for each 45 degree elbow. The vent system must also
be installed to prevent collection of condensate. Pitch horizontal
pipe runs downward 1 / in. per ft (21 mm/m) toward the outlet to
4
permit condensate drainage. See Fig. 99.
Insulate vent pipe exposed to cold air or routed through un-
heated areas. Also insulate vent pipe runs longer than 10 ft (3 m).
Insulation should be a minimum of
faced material suitable for temperatures up to 500 F (260 C).
Maintain 6 in. (152 mm) clearance between vent pipe and com-
bustible materials.
THIMBLE
5 FT. MIN.
(1.52 M)
2 FT. MIN.
(0.61 M)
CONDENSATE
DRAIN
TOTAL VERTICAL
FLUE HEIGHT
10 FT (3.05 M)
MAX (NOT TO
EXCEED 75%
VERTICAL FLUE
HEIGHT)
OPTIONAL
VENT KIT
Category I Vertical Furnace Venting (through Roof)
(Manifold furnace vents acceptable)
Fig. 98 — Indoor Vertical Venting
1 / in. (12.7 mm) thick, foil-
2
LISTED VENT TERMINAL
USE INSULATED VENT OUTDOORS
ROOF
1/4 IN. (6 mm) PITCH PER
1 FT. (305 mm) HORIZONTAL
RUN
SEE VENT PIPE
DIAMETER TABLE FOR
VENT DIAMETER
AIR-HANDLING UNIT
CONDENSATE
DRAIN
A vent cap listed for horizontal venting must be provided.
Vent cap inlet diameter must be same as the required vent pipe
diameter. The vent terminal must be at least 12 in. (305 mm)
from the exterior wall that it passes through to prevent degrada-
tion of building material by flue gases.
The vent terminal must be located at least 1 ft (305 mm)
above grade, or in snow areas, at least 3 ft (1 m) above snow line
to prevent blockage. Additionally, the vent terminal must be in-
stalled with a minimum horizontal clearance of 4 ft (1.2 m) from
electric meters, gas meters, regulators or relief equipment.
Each duct furnace must have its own individual vent pipe
and terminal. Do not connect vent system from horizontally
vented units to other vent systems or a chimney.
IMPORTANT: Through the wall vents shall not termi-
nate over public walkways, or over an area where con-
densate or vapor could create a nuisance or hazard.
115
a39-4396