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272312-UIM-A-0407
SECTION III: FILTERS
FILTER INSTALLATION
All applications require the use of an external filter. All filters and mount-
ing provision must be field supplied. Refer to Tables 5 & 16 for acces-
sory external filter kit options.
TABLE 5: Recommended Filter Sizes
Cabinet Size Side (in)
Side (cm)
A
16 x 25
40.6 x 64.0
B
16 x 25
40.6 x 64.0
C
(2) 16 x 25 (2) 40.6 x 64.0
NOTES:
1. Air velocity through throwaway type filters may not exceed 300 feet
per minute. All velocities over this require the use of high velocity fil-
ters.
2. Air flows above 1800 CFM require either return from two sides or
one side plus bottom.
SIDE RETURN - EXTERNAL INSTALLATION
Locate and knock out the square corner locators. These indicate the
size of the cutout to be made in the furnace side panel. Refer to Figure 4.
FIGURE 4: Side Return Cutout Markings
Install the side filter rack following the instructions provided with that
accessory. If a filter(s) is provided at another location in the return air
system, the ductwork may be directly attached to the furnace side
panel.
IMPORTANT: Some accessories such as electronic air cleaners and
pleated media may require a larger side opening. Follow the instruc-
tions supplied with that accessory for side opening requirements. Do
not cut the opening larger than the dimensions shown in Figure 1.
HORIZONTAL APPLICATION
Horizontal Filters
All filters and mounting provision must be field supplied. Filters(s) may
be located in the duct system external to the furnace or in a return filter
grille(s). Filters(s) may be located in the duct system using an external
duct filter box attached to the furnace plenum. Any branch duct (rectan-
gular or round duct) attached to the plenum must attach to the vertical
plenum above the filter height. The use of straps and / or supports is
required to support the weight of the external filter box.
IMPORTANT: Air velocity through throwaway type filters must not
exceed 300 feet per minute (91 m/min). All velocities over this require
the use of high velocity filters. Refer to Table 15.
All installations must have a filter installed.
8
Bottom (in) Bottom (cm)
14 x 25
35.6 x 64.0
16 x 25
40.6 x 64.0
20 x 25
50.8 x 64.0
FRONT OF
FURNACE
CORNER
MARKINGS
SECTION IV: GAS PIPING
GAS SAFETY
An overpressure protection device, such as a pressure regulator,
must be installed in the gas piping system upstream of the furnace
and must act to limit the downstream pressure to the gas valve so it
does not exceed 0.5 PSI (14" w.c. (3.48 kPa). Pressures exceeding
0.5 PSI (14" w.c. (3.48 kPa) at the gas valve will cause damage to
the gas valve, resulting in a fire or explosion or cause damage to
the furnace or some of its components that will result in property
damage and loss of life.
HIGH STAGE REGULATOR
ADJUSTMENT
OUTLET
PRESSURE
PORT
INLET
WRENCH
BOSS
INLET
PRESSURE
PORT
ON OFF
SWITCH
FIGURE 5: Gas Valve
IMPORTANT: Plan your gas supply before determining the correct gas
pipe entry. Use 90-degree service elbow(s), or short nipples and con-
ventional 90-degree elbow(s) to enter through the cabinet access holes.
GAS PIPING INSTALLATION
Properly sized wrought iron, approved flexible or steel pipe must be
used when making gas connections to the unit. If local codes allow the
use of a flexible gas appliance connection, always use a new listed con-
nector. Do not use a connector that has previously serviced another gas
appliance.
Some utility companies or local codes require pipe sizes larger than the
minimum sizes listed in these instructions and in the codes. The fur-
nace rating plate and the instructions in this section specify the type of
gas approved for this furnace - only use those approved gases. The
installation of a drip leg and ground union is required. Refer to Figures 6
& 7.
EXTERNAL MANUAL
SHUTOFF VALVE
TO GAS
SUPPLY
GROUNDED JOINT UNION
DRIP
MAY BE INSTALLED
LEG
INSIDE OR OUTSIDE UNIT.
FIGURE 6: Upflow Gas Piping
VENT
PORT
OUTLET
LOW STAGE REGULATOR
ADJUSTMENT
TO GAS
SUPPLY
Unitary Products Group
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