5
Do not locate unit near building ventilators or exhausts, or areas where corrosive chemical vapors can
be drawn into combustion air supply.
Do not install units in locations where flue products can be drawn in the adjacent building openings
such as windows, fresh air intakes, etc.
Indoor Installations
Location
Locate heating unit to ensure an adequate supply of fresh air to replace air used in the combustion and ventilation
process. The heating unit must be installed in a location with adequate clearances to provide for adequate
combustion air space, service and inspection, and proper clearances from combustible construction. The heating unit
shall be located in such a manner that it does not interfere with the circulation of air in the heated space.
Venting Indoor Installations
Furnace modules must be connected to a venting system to convey flue gases outside of the heated space.
Proper venting of the heating units is the responsibility of the installer. Venting materials are provided by others.
Vertically Vented Duct Furnaces – Category I (See Figure 3)
Non-condensing appliances operating at negative pressure are classified Category I. Category I Vent systems must be sized
and installed in accordance with the National Fuel Gas Code, ANSI Z223.1 (NFPA 54) Chapter 13 in the United
States or CAN/CGA-B149 Natural and propane gas installation code, Section 8 and Annex C, in Canada. UL Listed
Type B Vent or single wall metal pipe may be used. If used, single wall vent pipe shall have seams and joints sealed with
pressure sensitive aluminum tape or silicone rubber sealant, rated for 480 oF (249 oC) or higher. Joints should be secured with at
least two corrosion resistant fasteners. When custom designed systems provided by a vent system manufacturer are field
installed, proper heating unit operation must be verified, including flue gas analysis of each heater.
1. Maximize the height of the vertical run of vent pipe. A minimum of five (5) feet (1.5m) of vertical pipe is required.
The top of the vent pipe must extend at least 18 in. ( 457 mm) above the highest point on the roof. (Use Listed
Type B vent for external runs).
2. An approved weatherproof vent cap must be installed to the vent termination.
3. Horizontal runs should be pitched upward ¼” per foot (21mm/m) and should be supported at 3 foot (1m)
maximum intervals. It is best to keep horizontal runs less than 75% of vertical height to avoid possible need to
upsize vent pipe.
4. Design vent pipe runs to minimize the use of elbows. Each 90o elbow is equivalent to 5 feet (1.5m) to 7 feet
(2.13m) of straight vent pipe run depending on pipe diameter.
5. Vent pipe should not be run through unheated spaces. If such runs cannot be avoided, insulate vent pipe to
prevent condensation inside vent pipe. Insulation should be a minimum of ½” (12.7mm) thick, foil faced material
suitable for temperatures up to 500 oF (260 oC).
6. Dampers must not be used in vent piping runs. Spillage of flue gases into the occupied space could result.
7. Vent connectors serving Category 1 heaters must not be connected into any portion of a mechanical draft system
operating under positive pressure.
Gas-fired furnaces are not designed for use in hazardous atmospheres
containing flammable vapors or combustible dust, in atmospheres containing
chlorinated or halogenated hydrocarbons, or in applications with airborne
substances containing silicone.
