combustion and ventilation air in accordance with Section 5.3, Air for Combustion and Ventilation of the National Fuel Gas Code, ANSI Z223.1 (in U.S.A.) or Sections 7.2, 7.3 or
7.4of Gas Installation Codes
Do not permit overhanging structures or shrubs to obstruct outdoor air discharge outlet, combustion air inlet or vent outlets.
DUCTWORK
Ductwork should be designed and sized according to the methods in Manual Q of the Air Conditioning Contractors of America (ACCA).
A closed return duct system shall be used. This shall not pre- clude use of economizers or outdoor fresh air intake. The supply and return air duct connections at the unit should be made with flexible joints to minimize noise.
The supply and return air duct systems should be designed for the CFM and static requirements of the job. They should NOT be sized to match the dimensions of the duct connec-
tions on the unit.
When fastening ductwork to side duct flanges on unit, insert screws through duct flanges only. DO NOT insert screws through casing.
Outdoor ductwork must be insulated and water- proofed.
Refer to Figure 10 and 12 for information concerning side and bottom supply and return air duct openings.
FIGURE 3 : FIXED OUTDOOR AIR DAMPER
Gasketing and mounting screws are provided in a parts bag attached to the hood assembly. Apply gasketing to the three flange surfaces on the hood prior to installing the hood. Extend gasketing 1/4" beyond the top and bottom of the two side flanges to insure adequate sealing.
Adjusting the damper to the desired air flow may be done before mounting the hood into position or (after installation) by removing the front hood panel or the screen on the bottom of the hood. Damper baffle in position 1 will allow approxi- mately 10% recirculated air flow, position 2 approximately 15% and, to allow approximately 25%, remove the damper baffle.
On units with bottom return air applications, install the damper assembly over the opening in the side return air access panel. Remove and discard the opening cover and the covering over the hood mounting holes (used for ship- ping) before installing. Secure with the screws provided.
On units with side return air applications, install the damper assembly on the return air ductwork as close to the unit as possible. Cut an opening 16" high by 18" wide in the ductwork to accommodate the damper. Using the holes in the hood flanges as a template, drill 9/64" dia. (#26 drill) holes into the
ductwork and secure with the screws provided.
FIXED OUTDOOR AIR INTAKE DAMPER
This damper is shipped inside the return air compartment. It is completely assembled and ready for installation. A damper baffle inside of the hood is adjustable to provide variable amounts of outdoor air intake on units that are not provided with an economizer or a motorized damper option. Refer to Figure 3.
If outdoor air intake will not be required on units with bottom return air applications, the damper assembly should still be mounted on the side return air access panel, per the instructions above, to insure moisture is not drawn into the unit during operation. The covering over the mounting holes only need be removed. Do not remove the opening cover.
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