Installation and Maintenance Manual

Installation: Piping
GTND-SVX01B-EN 25
Standard Combustion
All Unit Sizes: Vertically Vented Unit
Heaters (Category I)
Observe the following precautions when venting the unit:
1. Use flue pipe of the same size as the flue connections
on the gas unit heater:
• Unit sizes 30–120: Use 4” (120 mm) flue pipe.
• Unit sizes 150–400: Refer to Table 2, p. 14.
All heaters must vented with UL Listed Type B vent (or,
for unit sizes 30–120, single wall vent), a factory built
chimney, or a lined brick and mortar chimney that has
been constructed in accordance with the National
Building Code.
Unit sizes 30–120: All tables and dimensions assume B
vent for the flue and single wall pipe or B vent for the
connector.
2. Unit sizes 30–120: Unit may be common vented when
installed in accordance with NFPA-54 guidelines.
3. Provide as long a vertical run o
f flue pipe at the gas unit
heater as possible. A minimum of 5 feet (1.5 m) of
ver
tical flue is required for Category I venting. The top
of the vent pipe should extend at least 2 feet (0.61 m)
abo
ve the highest point on the roof. Consideration
should be made for anticipated snow depth.
Unit sizes 150–400: In
stall an Amerivent Americap or
Metalbestos vent cap over the vent opening.
4. Slope horizontal runs upward from
the gas unit heater
at least 1/4-inch per foot (21-mm/m) minimum.
Horizontal Vent Connector length should not exceed
75% of the vertical height of the vent pipe, or chimney,
above the flue pipe connection. Maximum vent
connector length is 10 feet (3 m). For exceptions see
Ch. 10 of the National Fuel Gas Code, ANSI Z223.1.
Horiz
ontal portions of the venting system shall be
supported at maximum intervals of 4 feet (1.2 m): see
Figure 22, p. 26; in Canada, support at 3-foot intervals
(1-m) minimum intervals. Maintain clear
ance between
the vent pipe and combustible materials per vent pipe
manufacturer’s instructions.
5. Use as few elbows as possible.
6. Seal all vent pipe joints and se
ams to prevent leakage.
Use General Electric RTV-108, Dow-Corning RTV-732,
or equivalent silicone sealant with a temperature
rating of 500°F, or 3M #425 aluminum foil
tape (or
equivalent). Tape flue pipe joints with high-temp, RTV
or foil face tape.
7. Avoid running vent pipe through unheated spaces.
Wh
en this cannot be avoided, insulate the pipe to
prevent condensation of moisture on the walls of the
pipe. Insulate vent pipe runs longer than 10 ft (3 m).
In
sulation should be a minimum of 1/2” (12.7 mm)
thick foil faced.
8. Do not damper the flue piping. Failure to open such a
d
amper prior to operating the gas unit heater will result
in the spillage of flue gas into the occupied space.
9. Avoid installing units in areas under negative pressure
du
e to large exhaust fans or air conditioning. When
required, a flue vent fan should be installed in
accordance with the instructions included with the fan.
10. Vent connectors serving Category I and Category II
h
eaters shall not be connected into any portion of
mechanical draft systems operating under positive
pressure.
WARNING
Carbon Monoxide!
Never operate unit heaters without combustion air and
flue gas piping in place. Each unit heater MUST have its
own combustion air system and MUST NOT be
connected to other vent systems or to a chimney. Your
venting system must not be blocked by any snow, snow
drifts, or any foreign matter. Inspect your venting
system to ensure adequate ventilation exists at all
times! Failure to follow these recommendations could
result in death or serious injury.
WARNING
Risk of Fire and Carbon Monoxide
Poisoning with Improper Piping!
Never use a pipe of diameter other than that specified:
• Unit sizes 30–120: Use 4” (120 mm) flue pipe.
• Unit sizes 150–400: Refer to Table 2, p. 14!
To prevent pipe from melting and introducing exhaust
fumes into the air supply, never use PVC, ABS or any
other non-metallic pipe for venting! To prevent fan
restriction, an elbow should never be attached directly
to the venter. Failure to follow these recommendations
could result in death or serious injury or equipment
damage.