V-System Service Checks - Lennox LGM Series Manual

V- SYSTEMS SERVICE CHECKS
A-Heating System Service Checks
All LGM units are ETL/CSA design certified without
modification.
Before checking piping, check with gas company or au-
thorities having jurisdiction for local code requirements.
Refer to the LGM Installation, Operation and Maintenance
instruction for more information.
1-Gas Piping
Gas supply piping must not allow more than 0.5"W.C.
(124.3 Pa) drop in pressure between the gas meter and
the unit. Supply gas pipe must not be smaller than the
unit gas connection. Refer to installation instructions for
details.
2-Testing Gas Piping
NOTE-In case emergency shutdown is required, turn off
the main manual shut-off valve and disconnect the main
power to the unit. These controls should be properly la-
beled 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. (3481 Pa)].
See figure 26.
When checking piping connection for gas leaks, use the
preferred means. Common kitchen detergents can cause
harmful corrosion on various metals used in gas piping.
The use of specialty Gas Leak Detector is strongly rec-
ommended. It is available through 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.
GAS PIPING COMPONENTS
REFER TO INSTALLATION INSTRUCTIONS
GROUND
JOINT UNION
MANUAL MAIN
SHUT-OFF VALVE
(REFER TO LOCAL CODES)
FIGURE 26
3-Testing Gas Supply Pressure
When testing gas supply pressure, connect test gauge to
the inlet pressure tap located on unit gas valve GV1 and
or GV3. Test supply gas pressure with unit firing at maxi-
mum rate (both stages energized).
VALVE
CAP HERE
UNIT
TO ISOLATE
VALVE WHEN
PRESSURE
TESTING
LINE
ROOF
MOUNTING
FRAME
DRIP LEG
GAS PIPING
SUPPORT
Make sure the reading falls within the range of the follow-
ing values. Low pressure may result in erratic operation or
"underfire." High pressure can result in permanent dam-
age to the gas valve or "overfire." See table 20 for supply
pressures.
On multiple unit installations, each unit should be checked
separately while operating at maximum rate, beginning
with the one closest to the supply gas main and progress-
ing to the one furthest from the main. Multiple units should
also be tested with and without the other units operating.
Supply pressure must fall within the range listed in the
previous paragraph.
4-Check and Adjust Manifold Pressure
After line pressure has been checked and adjusted, check
manifold pressure. Move test gauge to the outlet pressure
tap located on unit gas valve GV1 and or GV3. See figure
25 for location of pressure tap on the gas valve.
The manifold pressure is factory set and should not re-
quire adjustment. If manifold pressure is incorrect and no
other source of improper manifold pressure can be found,
the valve must be replaced. See figure 25 for location of
gas valve (manifold pressure) adjustment screw.
All gas valves are factory regulated. The gas valve should
completely and immediately cycle off in the event of gas
or power failure. The manual shut-off knob can be used to
immediately shut off gas supply.
For safety, connect a shut-off valve between the
manometer and the gas tap to permit shut off of gas
pressure to the manometer.
Manifold Adjustment Procedure
1 - Connect test gauge to the outlet pressure tap on the
gas valve. Start the unit (call for second stage heat)
and allow five minutes for the unit to reach steady
state.
2 - While waiting for the unit to stabilize, notice the
flame. The flame should be stable without flashback
and should not lift from the burner heads. Natural
gas should burn basically blue with some clear
streaks. L.P. gas should burn mostly blue with some
clear yellow streaks.
3 - After allowing the unit to stabilize for five minutes,
record the manifold pressure and compare to the
values given in table 20.
Disconnect heating demand as soon as an accurate
reading has been obtained.
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CAUTION
CAUTION