Sterling TD - Manual (Page 2)

2
VENTING FOR POWER VENTED DUCT FURNACES (CATEGORY III)
GENERAL GUIDELINES
All duct furnaces 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 for power vented units. Refer to Figures 3a, 3b, 4a, 4b, 5a, and 5b. For installations in Canada, see
page 3.
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).
NOTICE: All vertical and horizontal venting arrange-
ments for the Tubular Duct Furnace are Category III
venting.
ANSI now organizes vented appliances into four
categories.
Venting Categories
Non
Condensing Condensing
Negative
Vent Pressure
I II
Positive
Vent Pressure
III
IV
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.
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.
Vent pipe material must be in compliance with UL 1738
for installations in the United States, and UL S636 for
installations in Canada.
Refer to Table 1 for vent termination clearance
requirements.
Through the wall vents for these appliances shall NOT
terminate over public walkways, or over an area where
condensate or vapor could create a nuisance or hazard
or could be detrimental to the operation of regulators,
relief valves, or other equipment.
The vent pipe equivalent length must be 5 feet (1.5m)
minimum and must not exceed 50 feet (15.2m).
Equivalent length is the total length of straight
sections PLUS 10 feet (3.05m) for each 90 degree
elbow, and 4 feet (1.22M) for each 45 degree elbow.
Maintain 6 inch (152mm) between vent pipe and
combustible materials. A minimum of 12 inch (305mm)
of straight pipe is required from the venter outlet before
installing an elbow in the vent system. An elbow should
never be attached directly to the venter!
Never use a pipe of a diameter other
than that specifi ed in Table 1! Never use PVC or other
nonmetallic pipe for venting! To do so may result in
serious damage to the unit, severe personal injury,
or death.
Any run of single wall vent pipe exposed to cold air or
passing through an unheated space must be insulated
with insulation suitable to 550°F (288°C).
The vent system must be installed to prevent collection
of condensate. Vertical vent pipes should be equipped
with condensate drains. Pitch horizontal pipes down-
ward 1/4 inch per foot (21mm/m) toward outlet for
condensate drainage.
Horizontal portions of the venting system shall be
supported at maximum intervals of 4 feet (1.2m) to
prevent sagging. In Canada, support at a maximum
of 3 feet (1m) intervals.
Each unit must have an individual vent pipe and
vent terminal per furnace section! Each unit MUST
NOT be connected to other vent systems or to a
chimney.