Gas Piping - Lennox MERIT ML195UH Installation Instructions Manual

Gas Piping

CAUTION
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.
WARNING
Do not over torque (800 in-lbs) or under torque (350 in-
lbs) when attaching the gas piping to the gas valve.
1 - Gas piping may be routed into the unit through either
the left- or right-hand side. Supply piping enters into
the gas valve from the side of the valve as shown in
figure 55. Move Bellows grommet to side which gas
line enters. Ensure opposite gas line hole is plugged
with supplied plug. 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 figures 55 and 56.
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.
See figure 54.
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.
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
less than or equal to 1/2 psig (3.48 kPa, 14 inches w.c.).
MANUAL MAIN SHUT-OFF
VALVE WILL NOT HOLD
NORMAL TEST PRESSURE
1/8" N.P.T. PLUGGED TAP
When testing pressure of gas lines, gas valve must be
disconnected and isolated. See figure 54. Gas valves
can be damaged if subjected to pressures greater than
1/2 psig (3.48 kPa).
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.
Page 35
IMPORTANT
CAP
FURNACE
GAS VALVE
FIGURE 54
IMPORTANT
WARNING
ISOLATE