Gas Piping; Pressure Test Gas Piping - Lennox LHT156 Installation Instructions Manual

Connect Gas Piping
Before connecting piping, check with gas company or
authorities having jurisdiction
requirements. When installing gas supply piping, length
of run from gas meter must be considered in determining
pipe size for 0.5" w.c. (.12kPa) maximum pressure drop.
Do not use supply pipe smaller than unit gas connection.
For natural gas units, operating pressure at the unit gas
connection must be a minimum of 4.7" w.c. (1.17kPa)
and a maximum of 10.5" (2.60kPa) w.c. For LP/propane
gas units, operating pressure at the unit gas connection
must be a minimum of 11" w.c. (2.74kPa) and a maximum
of 13.5" w.c. (3.36kPa).
When making piping connections a drip leg should be
installed on vertical pipe runs to serve as a trap for
sediment or condensate. A 1/8" N.P.T. plugged tap is
located on gas valve for test gauge connection. Refer to
Heating Start-Up section for tap location. Install a ground
joint union between the gas control manifold and the
main manual shut-off valve. See figure 4 for gas supply
piping entering outside the unit. See figure 5 for gas
supply entering through bottom of unit.
Compounds used on threaded joints of gas piping shall be
resistant to the action of liquified petroleum gases.
OUTSIDE OF UNIT GAS PIPING
GROUND
JOINT UNION
MANUAL MAIN
SHUT-OFF VALVE
TO
GAS
SUPPLY
(REFER TO
LOCAL CODES)

GAS PIPING

SUPPORT
FIGURE 4
LHT/LDT156, 180, 240
for local code
TO GAS
VALVE
DRIP LEG
Page 8
BOTTOM ENTRY GAS PIPING
TO GAS
VALVE
EXISTING
SUPPLY
FIGURE 5

Pressure Test Gas Piping

When pressure testing gas lines, the gas valve must
be disconnected and isolated. Gas valves can be
damaged if subjected to more than 0.5 psig (3.48kPa).
See figure 6.
NOTE-Codes may require that manual main shut-off valve
and union (furnished by installer) be installed in gas line
external to unit. Union must be of the ground joint type.
After all connections have been made, check all piping
connections for gas leaks. Also check existing unit gas
connections up to the gas valve; loosening may occur
during installation. Use a leak detection solution or other
preferred means. Do not use matches candles or other
sources of ignition to check for gas leaks.
NOTE-In case emergency shut down is required, turn off
the main manual shut-off valve and disconnect main
power to unit. These devices should be properly labeled
by the installer.
GROUND
JOINT UNION
MANUAL MAIN
SHUT-OFF VALVE
DRIP LEG
CAP