13
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 flue pipe at the gas
unit heater as possible. A minimum of five feet
(1.5m) of vertical flue is required. The top of the
vent pipe should extend at least two 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).
Horizontal runs should not exceed 75% of the
vertical height of the vent pipe, or chimney, above
the flue pipe connection, up to a maximum length
of 10 feet (3m). Horizontal portions of the venting
system shall be supported at maximum intervals of
four feet (1.2m). (See Figure 6)
4. Use as few elbows as possible.
5. Tape flue pipe joints with fireproof paper or material.
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 flue 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 flue 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 specified
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 flu-like symptoms).
