Heating System Service Checks; A.g.a./C.g.a. Certification; Gas Piping; Testing Gas Piping - Lennox G24M SERIES Unit Information

IV--HEATING SYSTEM SERVICE CHECKS
A--A.G.A./C.G.A. Certification
All units are A.G.A. design certified without modifica-
tions. Refer to the G24M Operation and Installation
Instruction Manual for Information.
B--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.
Compounds used on gas piping threaded joints
should be resistant to action of liquefied petroleum
gases.
C--Testing Gas Piping
When pressure testing gas lines, the gas valve must be
disconnected and isolated. Gas valves can be dam-
aged if subjected to more than 0.5psig (14” W.C.). See
figure 20 If the pressure is equal to or less than 0.5psig
.
(14”W.C.), use the manual shut- -off valve before pres-
sure testing to isolate 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
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
When testing supply gas pressure, connect test gauge
to inlet pressure tap (field provided). See figure 20.
Check gas line pressure with unit firing at maximum
rate. Low pressure may result in erratic operation or
CAP
FIELD PROVIDED
LINE PRESSURE TAP
FIGURE 20
Lennox under part
underfire. High pressure can result in permanent dam-
age to gas valve or overfire. For natural gas units, op-
erating pressure at unit gas connection must be be-
tween 5.0” W.C. and 13.0” W.C. For L.P . gas units,
operating pressure at unit gas connection must be be-
tween 10.0” W.C. and 13.0” W.C.
On multiple unit installations, each unit should be
checked separately, with and without other units oper-
ating. Supply pressure must fall within range listed in
previous paragraph.
E--Check Manifold Pressure
After line pressure has been checked and adjusted,
check manifold pressure. Move pressure gauge to out-
let pressure tap located on unit gas valve (GV1).
Checks of manifold pressure are made as verification of
proper regulator adjustment. Manifold pressure for the
G24M can be measured at any time the gas valve is
open and is supplying gas to the unit. Normal manifold
pressure for natural gas units is 3.5 in. w.c. For LP/pro-
pane gas the correct manifold pressure is 9.5 in. w.c.
For safety, connect a shut-off valve between the
manometer and the gas tap to permit shut off of
gas pressure to the manometer.
Unit (Fuel)
Natural
L.P .
The gas valve is factory set and should not require ad-
justment. All gas valves are factory regulated. See
table 9.
Manifold Adjustment Procedure:
1 - - Connect a test gauge to outlet pressure tap on gas
valve. Start unit and allow 5 minutes for unit to
reach steady state.
2 - - While waiting for the unit to stabilize, notice the
number
flame. Flame should be stable and should not lift
from burner. Natural gas should burn blue. L.P . gas
should burn mostly blue with some orange streaks.
3 - - After allowing unit to stabilize for 5 minutes, re-
cord manifold pressure and compare to values
given in table 9.
NOTE- -Shut unit off and remove manometer as
soon as an accurate reading has been obtained.
Take care to replace pressure tap plug.
Page 17
IMPORTANT
TABLE 9
GAS VALVE REGULATION
Operating Pressure (outlet) in. W.C.
3.5 +0 - -0.3
9.5 + 0.5