12
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.
5.3.4 Specially 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 20-25
percent free area and metal louvers and grilles will have 60-75 percent
free area. Louvers and grilles shall be fixed in the open position or
interlocked with the equipment so that they are opened automatically
during equipment operation.
5.3.6 Special 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 5.3.3-a.
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
G
ENERAL
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
D
RAIN
T
RAP
AND
L
INES
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.
L
EVELING
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.
A
LTERNATE
V
ENT
/F
LUE
AND
C
OMBUSTION
A
IR
C
ONNECTIONS
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.
