Sterling SF - Manual (Page 13)

13
VENTING
Observe the following precautions when venting the unit:
1. Use
fl ue pipe of the same size as the fl ue connections
on the gas unit heater (See Table #1). All heaters
should be vented with double wall or 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. Type B vent should
only be used for vertical rise portions of a Category
I vent pipe system. Type B vent should not be used
for horizontal runs of vent pipe.
2. Provide as long a vertical run of fl ue pipe at the gas
unit heater as possible. A minimum of 5 ft. (1.5m)
of vertical fl ue is required. The top of the vent pipe
should extend at least 2 ft. (0.61m) above the highest
point on the roof. Install a weather cap over the
vent opening. Consideration should be made for
anticipated snow depth.
3. Slope horizontal runs upward from the gas unit
heater at least 1/4 in. 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 ft. (3m). Horizontal portions of the venting system
shall be supported at minimum intervals of 4 ft.
(1.2m). In Canada, support at minimum intervals of
3 ft. (1m).
4. Use as few elbows as possible.
5. Seal all vent pipe joints and seams 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).
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 (NFPA 54), or applicable provisions of local
building codes. Refer to page 15 for Canadian installations. Refer to Figures 6A, 6B, 7A, 7B, 8A and 8B.
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).
Do not damper or add heat recovery devices to the fl ue piping. Failure to open such a damper prior to operating
gas unit will result in the spillage of fl ue gas into the occupied space.