Heating System Service Checks - Lennox SL280UHNX Series Unit Information

C-Safety or Emergency Shutdown
Turn off unit power. Close manual and main gas valves.
D-Extended Period Shutdown
Turn off thermostat or set to "UNOCCUPIED" mode. Close
all gas valves (both internal and external to unit) to guar-
antee no gas leak into combustion chamber. Turn off pow-
er to unit. All access panels and covers must be in place
and secured.
IV-HEATING SYSTEM SERVICE CHECKS
A-CSA Certification
All units are CSA design certified without modifications.
Refer to the SL280UHV(X) Installation Instruction.
B-Gas Piping
IMPORTANT
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.
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.
Compounds used on gas piping threaded joints should be
resistant to action of liquefied petroleum gases.
C-Testing Gas Piping
IMPORTANT
In case emergency shutdown is required, turn off the
main shut-off valve and disconnect the main power
to unit. These controls should be properly labeled
by the installer.
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 (14" W.C.). See FIGURE
21. If the pressure is greater than 0.5psig (14"W.C.), use
the manual shut-off valve before pressure testing to iso-
late furnace from gas supply.
GAS PIPING TEST PROCEDURE
MANUAL MAIN SHUT-OFF VALVE
WILL NOT HOLD TEST PRESSURE
IN EXCESS OF 0.5 PSIG (14"W.C.)
GAS VALVE
When checking piping connections for gas leaks, use
preferred means. Kitchen detergents can cause harmful
corrosion on various metals used in gas piping. Use of a
specialty Gas Leak Detector is strongly recommended. It
is available through Lennox under part number 31B2001.
See Corp. 8411-L10, for further details.
Do not use matches, candles, flame or any other source of
ignition to check for gas leaks.
D-Testing Gas Supply Pressure
White Rodgers Gas Valve
An inlet post located on the gas valve provides access to
the supply pressure. See FIGURE 19. Back out the 3/32
hex screw one turn, connect a piece of 5/16 tubing and
connect to a manometer to measure supply pressure. See
TABLE 19 for supply line pressure.
Honeywell / Resideo Gas Valve
A threaded plug on the inlet side of the gas valve pro-
vides access to the supply pressure tap. See FIGURE 20.
Remove the threaded plug, install a field-provided barbed
fitting and connect a manometer to measure supply pres-
sure. See TABLE 19 for supply line pressure. Replace the
threaded plug after measurements have been taken.
E-Check Manifold Pressure
After line pressure has been checked and adjusted, check
manifold pressure. Move pressure gauge to outlet pres-
sure tap located on unit gas valve (GV1). Checks of man-
ifold pressure are made as verification of proper regulator
adjustment.
Manifold pressure can be measured at any time the gas
valve is open and is supplying gas to the unit. See TABLE
19 for normal operating manifold pressure.
For safety, connect a shut\-off valve between the
manometer and the gas tap to permit shut off of gas
pressure to the manometer.
Page 48
CAP
FIELD PROVIDED
LINE PRESSURE TAP
FIGURE 21
CAUTION