035-20646-001 Rev. A (1004)
8
Unitary Products Group
ATTIC INSTALLATION
This appliance is design certified for line contact when the furnace is
installed in the horizontal left or right position. The line contact is only
permissible between lines are formed by the intersection of the top and
two sides of the furnace and the building joists, studs or framing. This
line may be in contact with combustible material.
IMPORTANT:
In either a horizontal left or right installation, a minimum
of 8" (20.3 cm) clearance is required beneath the furnace to allow for
the installation of the condensate trap and drain pipe. Refer to "CON-
DENSATE PIPING" section of this manual for more information.
SUSPENDED FURNACE / CRAWL SPACE
INSTALLATION
The furnace can be hung from floor hoists or installed on suitable blocks
or pad. Blocks or pad installations shall provide adequate height to
ensure the unit will not be subject to water damage. Units may also be
suspended from rafters or floor joists using rods, pipe angle supports or
straps. Angle supports should be placed at the supply air end and near
the blower deck. Do not support at return air end of unit. All four sus-
pension points must be level to ensure quite furnace operation. When
suspending the furnace use a secure a platform constructed of plywood
or other building material secured to the floor joists. Refer top Figure 7
for typical crawl space installation.
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.
FIGURE 6:
Typical Attic Installation
When a furnace is installed in an attic or other insulated space,
keep all insulating materials at least 12 inches (30.5 cm) away from
furnace and burner combustion air openings.
If this furnace is installed over a finished space, a condensate
safety pan must be installed.
FIGURE 7:
Typical Suspended Furnace / Crawl Space Installation
LINE CONTACT ONLY PERMISSIBLE
BETWEEN LINES FORMED BY THE
INTERSECTION OF FURNACE TOP
AND TWO SIDES AND BUILDING
JOISTS, STUDS OR FRAMING
FILTER RACK MUST BE A
MINIMUM DISTANCE
OF 18” (45.7 cm)
FROM THE FURANCE
COMBUSTION
AIR
GAS
PIPING
VENT PIPE
(maintain required
clearances to
combustible)
RETURN
AIR
SUPPLY
AIR
12” CLEARANCE
FOR SERVICE
30” MIN.
WORK AREA
ANGLE IRON
BRACKET
1” MAX. BETWEEN
ROD & FURNACE
6” MIN. BETWEEN
ROD & FURNACE
1” MAX. BETWEEN
ROD & FURNACE
SUPPORT
BRACKET
In any application where temperatures below freezing are possible,
see “BELOW FREEZING LOCATIONS”.
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.
FIGURE 8:
Gas Valve
INLET
WRENCH
BOSS
INLET
PRESSURE
PORT
ON
OFF
ON/OFF SWITCH
(Shown in ON position)
MAIN REGULATOR
ADJUSTMENT
OUTLET
OUTLET
PRESSURE
PORT
VENT PORT
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
•
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 5:
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.
