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12
VENTING
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 (See Table #1).
All heaters should be vented with UL Listed Type
B vent, a factory built chimney, or a lined brick
and mortar chimney that has been constructed in
accordance with the National Building Code.
2. Provide as long a vertical run of fl ue pipe at the gas
unit heater as possible. A minimum of 5 feet (1.5m)
of vertical fl ue is required. The top of the vent pipe
should extend at least 2 feet (0.61m) above the
highest point on the roof. Install a weather cap over
the vent opening.
3. Slope horizontal runs upward from the gas unit
heater at least 1/4-inch per foot (21mm/m) minimum.
Horizontal runs should not exceed 75% of the
vertical height of the vent pipe, or chimney, above
the fl ue pipe connection, up to a maximum length
of 10 feet (3m). Horizontal portions of the venting
system shall be supported at maximum intervals of
4 feet (1.2m). (See Figure 6)
4. Use as few elbows as possible.
5. Tape fl ue pipe joints with high-temp, RTV or foil face
tape.
6. Avoid running vent pipe through unheated spaces.
7. When this cannot be avoided, insulate the pipe to
prevent condensation of moisture on the walls of the
pipe.
8. Do not damper the fl ue piping. Failure to open such
a damper 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 due to large exhaust fans or air conditioning.
When required, a fl ue vent fan should be installed in
accordance with the instructions included with the
fan.
10. Vent connectors serving Category I and Category
II heaters shall not be connected into any portion of
mechanical draft systems operating under positive
pressure.
ANSI now organizes vented
appliances into four categories.
Venting Categories
Non
Condensing Condensing
Negative
Vent I II
Pressure
Positive
Vent III IV
Pressure
VERTICALLY VENTED UNIT HEATERS (CATEGORY I)
Category I
Includes non-condensing
appliances with negative vent
pressure, like the traditional
atmospheric unit heater.
Category II
Groups condensing appliances
with negative vent pressure.
Category III
Appliances are non-condensing
and operate with a positive vent
pressure.
Category IV
Covers condensing appliances with
positive vent pressure.
NOTICE: Category II and IV do
not apply to equipment specifi ed
within this manual.
All unit heaters must be vented! All Venting installations shall be in accordance with the latest edition of Part 7,
Venting of Equipment of the National Fuel Gas Code, ANSI Z223.1, or applicable provisions of local building codes.
Refer to page 15 for Canadian installations. Refer to Figures 6, 7, 8A, 8B, 9A and 9B.
CARBON MONOXIDE! 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 heed these warnings could result in Carbon Monoxide Poisoning (symptoms include
grogginess, lethargy, inappropriate tiredness, or fl u-like symptoms).