Sterling SF - Manual (Page 4)

4
VENTING – GENERAL GUIDELINES (continued)
Do not damper or add heat recovery devices to the fl ue
piping. Failure to open such a damper prior to operating
the gas unit heater will result in the spillage of fl ue gas
into the occupied space.
Avoid installing units in areas under negative pressure.
When required, a fl ue vent fan should be installed in
accordance with the instructions included with the fan.
Vent connectors serving Category I and Category II
heaters shall not be connected into any portion of
mechanical draft systems operating under positive vent
pressure.
Maintain 1-inch (25.4mm) clearance between the vent
pipe and combustible materials.
Figure 3 – Side View Horizontal Vent
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.
NOTICE: Category II and IV do not apply to equipment
specifi ed within this manual.
Table 1
Vent SystemsTermination Clearance Requirements
Structure/Object
Minimum Clearances for
Termination Locations
USA CANADA
Door, window or gravity vent inlet or
combustion air inlet for other appliances
4 ft. below
4 ft. horizontally
1 ft. above
1 ft. (0.3m) for 100,000 BTUH
input or less. 3 ft. (0.9m) for
input exceeding 100,000
BTUH
Forced air inlet within 10 ft. 3 ft. above 6 ft. (1.8m)
Adjoining building or parapet 10 ft. 10 ft. (3.04m)
Adjacent public walkways 7 ft. above grade 7 ft. (2.1m) above grade
Electric, gas meters & regulators 4 ft. horizontal
3 ft. (0.9m) horizontally from
meter/regulator assembly. 6
ft. (1.8m), any direction, from
a gas service regulator vent
outlet
Above grade level* 1 ft. 1 ft. (0.3m)
* Minimum above maximum snow depth, or per local code, whichever is greatest.