GAMA Gas-Fired Furnace User's Information Manual - page 19
DUCTING
The proper sizing of warm air ducts is necessary to insure satisfactory heating operation. Ductwork should be in
accordance with the latest editions of (U.S.) NFPA-90A (Air Conditioning Systems) and NFPA-90B (Warm Air Heating
and Air Conditioning Systems) or Canadian equivalent.
Ductwork Recommendation:
The supply duct work should be attached to the
flanged opening provided at the discharge end of the
furnace. See page 3 "Furnace Specifications" for the
dimensions of this opening.
A left, right, or bottom return air opening must be
used as determined by the layout of the installation. An
externally mounted air filter is required.
This furnace has a two piece bottom panel. For
bottom or end duct return, remove the back portion of the
bottom panel by removing the four (4) screws - two (2) on
each side toward the back of the furnace (See Figure 7).
Tilt furnace toward the front, the back portion of the panel
will drop down. Then the back portion can be removed
by pulling toward the back of the furnace.
Figure 7
BOTTOM PANEL REMOVAL
Knockouts are provided on both sides of the furnace
to facilitate the cutout required to the return air ductwork.
Furnace cutouts must be the full size specified by the
corner markers. Undersized cutouts will adversely
affect the airflow capability of the furnace and could
cause overheating of the heat exchanger.
The following recommendations should be followed
when installing the ductwork:
1.
Install locking-type dampers in all branches of the
individual ducts to balance out the system. Dampers
should be adjusted to impose the proper static at the
outlet of the furnace.
2.
Noncombustible flexible duct connectors are
recommended to connect both the supply and return
ducts to the furnace.
3.
In cases where the return air grille is located close to
the blower inlet, there should be at least one 90° air
turn between blower and return grille. Further
reduction in sound can be accomplished by installing
acoustical air turning vanes and/or lining the inside of
the duct with acoustical material.
4.
It is recommended that the supply duct be provided
with a removable access panel. This opening shall
be accessible when the furnace is installed and shall
be of such a size that the heat exchanger can be
viewed for possible openings using light assistance or
a probe can be inserted by sampling the air stream.
The access panel shall be designed so as to prevent
leaks when locked in position. If an air conditioning
coil is installed, the access panel to the coil can be
used for this purpose.
When supply ducts carry air circulated by the
furnace to areas outside the spaces containing the
furnace, the return air shall also be handled by a
duct sealed to the furnace casing and terminating
outside the space containing the furnace. Incorrect
ductwork termination and sealing will create a
hazardous condition that could lead to bodily harm.
Air openings, intake and outlet pipes, return air
grilles and warm air registers must not be
obstructed.
Filters:
Air filters
must
be used in every installation. For side
return installations, air filters
must
be installed external to
the furnace casing. An external filter rack kit with filter
(parts No. 20069901 or Cat. No. 68L75 for 12 / 15½" x
25" sizes and 20069902 or Cat. No. 68L76 for 15½ / 19"
x 25" sizes) is available as an optional accessory.
For bottom (end) return installations, the above
optional external rack may be used, if the unit was not
provided with a internal filter. Minimum filter size and
suggested filter materials are shown in Table 2. (If
different type filter is used, it must be an equivalent high
airflow capacity.)
Table 2 EXTERNAL FILTER RACK SIZE
MODEL
SIDE
RETURN
BOTTOM/END
RETURN
050-3
075-3
15 ½ X 25
12 X 25
100-4
15 ½ X 25
15 ½ X 25
125-5
15 ½ X 25
19 X 25
20558801
Issue 0442
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