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 engi- neering, 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 blocking 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 fireplaces may create conditions requiring special attention to avoid unsatisfac- tory 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. 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:
FURNACE MUST BE LEVEL | ||
FROM END TO END | ||
ALTERNATE VENT/FLUE | FURNACE MUST BE LEVEL | |
AND COMBUSTION AIR | ||
INTAKE LOCATIONS | OR SLIGHTLY TILTED FORWARD | |
| WITH THE DOORS 0" - 3/4" | |
| BELOW THE BACK PANEL | |
| 4 3/4" MINIMUM | |
| DRAIN TRAP | |
GAS LINE WITH | CLEARANCE | |
DRIP LEG (3" MINIMUM) |
| |
DRAIN PAN | DRAIN LINE WITH 1/4" PER FOOT | |
DOWNWARD SLOPE | ||
| ||
FURNACE MUST BE SUPPORTED | 24" MINIMUM SERVICE | |
AT BOTH ENDS AND MIDDLE | CLEARANCE REQUIRED | |
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 mini- mum clearance of 4 3/4 inches below the furnace must be pro- vided for the drain trap. Additionally, the appropriate downward piping slope must be maintained from the drain trap to the drain location. Refer to Section X, 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 measures must be taken to prevent condensate from freezing.
LEVELING
Leveling ensures proper condensate drainage from the heat ex- changer 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, gen- erated 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 flue and com- bustion air piping are available for upflow furnaces with left dis- charge and counterflow furnaces with right air discharge. This con- figuration allows the flue and combustion air piping to be run verti- cally through the furnace. Refer to the “Recommended Installation Positions” figure for further detail. The standard piping connec- tions may also be used in these positions. Refer to Section IX, Vent/Flue Pipe and Combustion Air Pipe for details concerning the conversion to the alternate vent/flue and combustion air connec- tions.
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