035-19670-003 Rev. A (1004)
Unitary Products Group
7
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
7.
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. An accessory filter rack is available for mounting the filter exter-
nal to the cabinet.
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. Filters must be a mini-
mum distance of 18” (45.7 cm) from the furnace. Any branch duct (rect-
angular or round duct) attached to the plenum must attach to the
vertical plenum above the filter height. The use of straps and / or sup-
ports is required to support the weight of the external filter box.
SECTION IV: GAS PIPING
GAS SAFETY
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 furnace
rating plate and the instructions in this section specify the type of gas
approved for this furnace - only use those approved gases. The instal-
lation of a drip leg and ground union is required. Refer to Figures 9 or
10.
TABLE 5:
Filter Sizes
Cabinet Size
Side (in)
Side (cm)
Bottom (in)
Bottom (cm)
A
16 x 26
40.6 x 66.0
14 x 26
35.6 x 66.0
B
16 x 26
40.6 x 66.0
16 x 26
40.6 x 66.0
C
(2) 16 x 26
(2) 40.6 x 66.0
20 x 26
50.8 x 66.0
D
(2) 16 x 26
(2) 40.6 x 66.0
20 x 26
50.8 x 66.0
FIGURE 5:
Side Return Cutout Markings
All installations must have a filter installed.
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.
FRONT OF
FURNACE
CORNER
MARKINGS
FIGURE 6:
Gas Valve
R
E
P
L
A
C
E
R
E
P
L
A
C
E
SCRE
W
SCRE
W
INLET
OUTLET
ON / OFF SWITCH
WRENCH
BOSS
PM
C
HI
O
F
F
ON
CHECKING THE GAS PRESSURES
1.
The pressure ports on the gas valve are marked OUT P and IN
P.
2.
The manifold pressure must be taken at the port marked OUT P.
3.
The inlet gas supply pressure must be taken at the port marked
IN P.
4.
Using a 3/32” (0.2 cm) Allen wrench, loosen the set screw by
turning it 1 turn counter clockwise. DO NOT REMOVE THE
SET SCREW FROM THE PRESSURE PORT.
5.
Push one end the 3/8” (0.9 cm) ID flexible tubing over the pres-
sure port so that the body of the port is inside the tubing.
6.
Use a reducer connector to connect the 3/8” (0.9 cm) ID flexible
tube to a 1/4” (0.6 cm) ID flexible tube that is connected to a "U”
tube manometer or digital pressure measuring equipment.
IMPORTANT:
The inlet gas pressure operating range table specifies
what the minimum and maximum gas line pressures must be for the
furnace to operate safely. The gas line pressure
MUST BE
a mini-
mum of:
•
7” W.C. (1.74 kPA) for Natural Gas
•
11” W.C. (2.74 kPA) for Propane (LP) Gas
in order to obtain the BTU input specified on the rating plate and/or
the nominal manifold pressure specified in these instructions and on
the rating plate.
TABLE 6:
Inlet Gas Pressure Range
INLET GAS PRESSURE RANGE
Natural Gas
Propane (LP)
Minimum
4.5” W.C. (1.12 kPa)
8.0” W.C. (1.99 kPa)
Maximum
10.5” W.C. (2.61 kPa)
13.0” (3.24 kPa) W.C.
