268890-UIM-B-0607
Unitary Products Group
9
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 Figure 8.
IMPORTANT:
An accessible manual shutoff valve must be installed
upstream of the furnace gas controls and within 6 feet (1.8 m) of the fur-
nace.
The furnace must be isolated from the gas supply piping system by
closing its individual external manual shutoff valve during any pressure
testing of the gas supply piping system at pressures equal to or less
than 1/2 psig (3.5 kPa).
Gas piping may be connected from either side of the furnace using any
of the gas pipe entry knockouts on both sides of the furnace. Refer to
Figure 3 dimensions.
GAS ORIFICE CONVERSION FOR PROPANE (LP)
This furnace is constructed at the factory for natural gas-fired operation,
but may be converted to operate on propane (LP) gas by using a fac-
tory-supplied LP conversion kit. Follow the instructions supplied with
the LP kit. Refer to Table 6 or the instructions in the propane (LP) con-
version kit for the proper gas orifice size.
HIGH ALTITUDE GAS ORIFICE CONVERSION
This furnace is constructed at the factory for natural gas-fired operation
at 0 – 8,000 feet (0-m – 2,438 m) above sea level.
The manifold pressure must be changed in order to manitain proper
and safe operation when the furnace is installed in a location where the
altitude is greater than 8,000 feet (2,438 m) above sea level. Refer to to
Table 6 for proper manifold pressure settings.
HIGH ALTITUDE PRESSURE SWITCH CONVERSION
For installation where the altitude is less than 8,000 feet (2,438 m), it is
not required that the pressure switch be changed. For altitudes above
8,000 feet (2,438 m), see Field Installed Accessories - High Altitude
pressure Switch.
FIGURE 6:
Typical Suspended Furnace / Crawl Space Installation
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 exceed-
ing 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 7:
Gas Valve
ANGLE IRON
BRACKET
1” MAX. BETWEEN
ROD & FURNACE
6” MIN. BETWEEN
ROD & FURNACE
1” MAX. BETWEEN
ROD & FURNACE
SUPPORT
BRACKET
INLET
WRENCH
BOSS
INLET
PRESSURE
PORT
ON
OFF
ON/OFF SWITCH
(Shown in ON position)
MAIN REGULATOR
ADJUSTMENT
OUTLET
OUTLET
PRESSURE
PORT
VENT PORT
FIGURE 8:
Downflow Gas Piping
FIGURE 9:
Horizontal Gas Piping
Never apply a pipe wrench to the body of the gas valve when
installing piping. A wrench must be placed on the octagonal hub
located on the gas inlet side of the valve. Placing a wrench to the
body of the gas valve will damage the valve causing improper oper-
ation and/or the valve to leak.
EXTERNAL MANUAL
SHUTOFF VALVE
TO GAS
SUPPLY
TO GAS
SUPPLY
GROUNDED JOINT UNION
MAY BE INSTALLED
INSIDE OR OUTSIDE UNIT.
DRIP
LEG
MANUAL
SHUT-OFF
VALVE
GAS
PIPE
GAS
PIPE
DRIP
LEG
MANUAL
SHUT-OFF VALVE
GAS VALVE
GAS BURNERS
DRIP
LEG
