507762-01
Issue 1907
Page 34 of 46
Gas Piping
Gas supply piping should not allow more than 0.5” W.C.
drop in pressure between gas meter and unit. Supply gas
pipe must not be smaller than unit gas connection.
If a flexible gas connector is required or allowed by
the authority that has jurisdiction, black iron pipe shall
be installed at the gas valve and extend outside the
furnace cabinet. The flexible connector can then be
added between the black iron pipe and the gas supply
line.
CAUTION
Do not over torque (800 in-lbs) or under torque (350
in-lbs) when attaching the gas piping to the gas valve.
WARNING
1. Gas piping may be routed into the unit through the
right-hand side only. Supply piping enters into the gas
valve from the side of the valve as shown in Figure 57.
Connect the gas supply piping into the gas valve. The
maximum torque is 800 in lbs and minimum torque is
350 in lbs when when attaching the gas piping to the
gas valve.
2. When connecting gas supply, factors such as length
of run, number of fittings and furnace rating must be
considered to avoid excessive pressure drop. Table 9
lists recommended pipe sizes for typical applications.
NOTE:
Use two wrenches when connecting gas piping
to avoid transferring torque to the manifold.
3. Gas piping must not run in or through air ducts,
clothes chutes, chimneys or gas vents, dumb waiters
or elevator shafts. Center gas line through piping hole.
Gas line should not touch side of unit. See Figure 57
4. Piping should be sloped 1/4 inch per 15 feet (6mm per
5.6m) upward toward the gas meter from the furnace.
The piping must be supported at proper intervals, every
8 to 10 feet (2.44 to 3.05m), using suitable hangers or
straps. Install a drip leg in vertical pipe runs to serve as
a trap for sediment or condensate.
5. A 1/8” N.P.T. plugged tap or pressure post is located
on the gas valve to facilitate test gauge connection.
6. In some localities, codes may require installation of a
manual main shut-off valve and union (furnished by
installer) external to the unit. Union must be of the
ground joint type.
Compounds used on threaded joints of gas piping must
be resistant to the actions of liquified petroleum gases.
IMPORTANT
Leak Check
After gas piping is completed, carefully check all piping
connections (factory- and field-installed) for gas leaks. Use
a leak detecting solution or other preferred means.
Never use an open flame to test for gas leaks. Check all
connections using a commercially available soap solution
made specifically for leak detection.
The furnace must be isolated from the gas supply system
by closing its individual manual shut-off valve during any
pressure testing of the gas supply system at pressures
greater than or equal to 1/2 psig (3.48 kPa, 14 inches w.c.).
Isolate Gas Valve
Manual Main Shut-Off Valve Will
Not Hold Normal Test Pressure
1/8” N.P.T.
Plugged Tap
Cap
Figure 56.
When testing pressure of gas lines, gas valve must be
disconnected and isolated. See Figure 56. Gas valves
can be damaged if subjected to pressures greater than
1/2 psig (3.48 kPa).
IMPORTANT
FIRE OR EXPLOSION HAZARD
Failure to follow the safety warnings exactly could
result in serious injury, death, or property damage.
Never use an open flame to test for gas leaks. Check
all connections using a commercially available soap
solution made specifically for leak detection. Some
soaps used for leak detection are corrosive to certain
metals. Carefully rinse piping thoroughly after leak test
has been completed.
WARNING
