Combustion and Ventilation Air Requirements
To avoid property damage, personal injury or death,
sufficient fresh air for proper combustion and ventilation
of flue gases must be supplied. Most homes require
outside air be supplied into the furnace area.
Improved construction and additional insulation in buildings have
reduced heat loss by reducing air infiltration and escape around
doors and windows. These changes have helped in reducing
heating/cooling costs but have created a problem supplying
combustion and ventilation air for gas-fired and other
fuel-burning appliances. Appliances that pull air out of the house
(clothes dryers, exhaust fans, fireplaces, etc.) increase the
problem by starving appliances for air.
House depressurization can cause back drafting or improper
combustion of gas-fired appliances, thereby exposing building
occupants to gas combustion products that could include carbon
If this furnace is to be installed in the same space with other gas
appliances, such as a water heater, ensure there is an adequate
supply of combustion and ventilation air for the other appliances.
Refer to the latest edition of the National Fuel Gas Code NFPA
54/ANSI Z223.1 or CAN/CSA B149 Installation Codes or
applicable provisions of the local building codes for determining
the combustion air requirements for the appliances.
Most homes will require outside air to be supplied to the furnace
area by means of ventilation grilles or ducts connecting directly
to the outdoors or spaces open to the outdoors such as attics or
This furnace may be installed in an upright position or horizontal
on either the left or right side panel.
NOTE: Do not install this furnace on its back.
For upright upflow furnaces, the return air ductwork may be
attached to the side panel(s) and/or base pan.
For horizontal upflow furnaces, the return air ductwork must be
attached to the base pan.
For both the upright or horizontal counterflow furnaces, the
return air ductwork must be attached to the base pan (top end of
the blower compartment).
NOTE: Do not attach the ductwork to the back of the furnace.
Contact your local distributor for the proper airflow requirements
and the number of required ductwork connections. See the
"Recommended Installation Positions" illustrations for the
appropriate installation positions, ductwork connections and the
resulting airflow arrangements.
Horizontal applications, in particular, may dictate many of the
installation's specifics such as airflow direction, ductwork
connections, 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:
Drain trap and lines
Leveling the furnace
Alternate vent/flue and combustion air connections
Alternate electrical and gas line connections
A. Alternate vent/flue location
B. Level end-to-end
C. Level side-to-side or slightly
tilted—doors 0" to ³⁄₄ " (1.9 cm)
below back panel
D. Drain line— ¹⁄₄ " (6.4 mm) per
foot downward slope
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 clearance of 4³⁄₄" (12.1 cm) below the furnace must be
provided for the drain trap. Additionally, the appropriate
downward piping slope must be maintained 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 measures must
be taken to avoid condensate from freezing.
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 sloping downward ³⁄₄" (1.9 cm)
lower than 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 Connections
In horizontal installations, provisions for alternate flue and
combustion air piping are available for upflow furnaces with left
discharge and counterflow furnaces with right air discharge. This
configuration allows the flue and combustion air piping to be run
vertically through the side of the furnace. Refer to the
"Recommended Installation Positions" illustrations for further
details. The standard piping connections may also be used in
E. 24" (61 cm) minimum service
F. 4 ³⁄₄ " (12.1 cm) minimum drain trap
G. Supports at both ends and middle
H. Drain pan
I. Gas line with 3" (7.6 cm) minimum