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17
VENTING - GENERAL GUIDELINES
Venting Categories
Non
Condensing Condensing
Negative
Vent I II
Pressure
Positive
Vent III IV
Pressure
The following guidelines apply to all categories to
follow.
Table 4
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 flue 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.
ADDITIONAL REQUIREMENT
FOR CANADIAN INSTALLATIONS
REFER TO SPECIFICATION TABLE AND INSTALLA-
TION MANUAL FOR PROPER USAGE.
*The following instructions apply to Canadian
installations in addition to installation and operating
instructions.
1. Installation must conform with local building codes, or in
the absence of local codes, with current CGA B149.1,
Installation Codes for Natural Gas Burning Appliances
and Equipment, or CGA B149.2, Installation Codes for
Propane Gas Burning Appliances and Equipment.
2. Any reference to U. S. standards or codes in these
instructions are to be ignored, and the applicable
Canadian standards or codes applied
Minimum Clearances for
Termination Locations
Structure
Vent Systems
Termination Clearance Requirements
Door, window or any gravity vent inlet
Forced air inlet within 10 ft.
Adjoining building or parapet
Adjacent public walkways
Electric, gas meters & regulators
4 feet below
4 feet horizontally
1 foot above
3 feet above
6 feet
7 feet above grade
4 feet horizontal
ANSI now organizes vented appliances into four
categories.
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 equip-
ment specifi ed within this manual.