5.When directly communicating with the outdoors, the single open- ing shall have a minimum free area of 1 square inch per 3,000 BTU per hour of total input rating of all equipment in the enclo- sure.
5.3.4Specially Engineered Installations:
The requirements of 5.3.3 shall not necessarily govern when special engineering, approved by the authority having jurisdiction, provides an adequate supply of air for combustion, ventilation, and dilution of flue gases.
5.3.5 Louvers and Grilles:
In calculating free area in 5.3.3, consideration shall be given to the block- ing effect of louvers, grilles or screens protecting openings. Screens used shall not be smaller than 1/4 inch mesh. If the area through a design of louver or grille is known, it should be used in calculating the size of opening required to provide the free area specified. If the design and free area is not known, it may be assumed that wood louvers will have
5.3.6Special Conditions Created by Mechanical Exhausting or Fire- places:
Operation of exhaust fans, ventilation systems, clothes dryers, or fire- places may create conditions requiring special attention to avoid unsat- isfactory operation of installed gas utilization equipment. Air from Inside Building. See
VI. INSTALLATION POSITIONS
This furnace may be installed in an upright position or horizontal on either the left or right side panel. Do not install this furnace on its back. For upright upflow furnaces, return air ductwork may be attached to the side panel(s) and/or basepan. For horizontal up- flow furnaces, return air ductwork must be attached to the basepan. For both upright or horizontal counterflow furnaces, return duct- work must be attached to the basepan (top end of the blower com- partment). NOTE: Ductwork must never be attached to the back of
the furnace. For upflow installations requiring 1,800 CFM or more, use either two side returns or a bottom return or a combination of side and bottom. Contact your distributor for proper airflow require- ments and number of required ductwork connections. Refer to “Recommended Installation Positions” figure for appropriate in- stallation positions, ductwork connections, and resulting airflow arrangements.
VII. HORIZONTAL APPLICATIONS & CONSIDERATIONS
GENERAL
Horizontal applications, in particular, may dictate many of the installation’s specifics such as airflow direction, ductwork connec- tions, flue and combustion air pipe connections, etc. The basic application of this furnace as a horizontal furnace differs only slightly from an upright installation. When installing a furnace horizontally, additional consideration must be given to the following:
LOCATION
Horizontal Furnace
DRAIN TRAP AND LINES
In horizontal applications the condensate drain trap is secured to the furnace side panel, suspending it below the furnace. A minimum clear- ance of 4 3/4 inches below the furnace must be provided for the drain trap. Additionally, the appropriate downward piping slope must be main- tained from the drain trap to the drain location. Refer to Condensate Drain Trap and Lines for further details. If the drain trap and drain line will be exposed to temperatures near or below freezing, adequate mea- sures must be taken to prevent condensate from freezing.
LEVELING
Leveling ensures proper condensate drainage from the heat exchanger and induced draft blower. For proper flue pipe drainage, the furnace must be level lengthwise from end to end. The furnace should also be level from back to front or have a slight tilt with the access doors downhill (approximately 3/4 inches) from the back panel. The slight tilt allows the heat exchanger condensate, generated in the recuperator coil, to flow forward to the recuperator coil front cover.
ALTERNATE VENT/FLUE AND COMBUSTION AIR CONNECTIONS
In horizontal installations, provisions for alternate vent/flue piping is available for upflow furnaces with left air discharge. Counterflow fur- naces include provisions for both alternate vent/flue and combustion air piping with right air discharge. These configurations allow the flue and combustion air piping to be run vertically through the furnace. Re- fer to the “Recommended Installation Positions” figure for further de- tail. The standard piping connections may also be used in these posi- tions. Refer to Vent/Flue Pipe and Combustion Air Pipe for details concerning the conversion to the alternate vent/flue air connections.
When using the horizontal alternate vent configuration, you must use the RF000142 vent drain kit. See following illustration.
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