Lennox EL297UH090XV48C - IV-HEATING SYSTEM SERVICE CHECKS

Page 80
IV-HEATING SYSTEM SERVICE CHECKS
A-CSA Certication
All units are CSA design certied without modications.
Refer to the EL297UHV(X) Installation Instruction.
B-Gas Piping
CAUTION
If a exible 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.
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 liqueed petroleum gases.
C-Testing Gas Piping
IMPORTANT
In case emergency shutdown is required, turn o󰀨 the
main shut-o󰀨 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
53. If the pressure is greater than 0.5psig (14”W.C.), use
the manual shut-o󰀨 valve before pressure testing to iso-
late furnace from gas supply.
MANUAL MAIN SHUT-OFF
VALVE WILL NOT HOLD
NORMAL TEST PRESSURE
CAP
FURNACE
ISOLATE
GAS VALVE
1/8” N.P. T. PLUGGED TA P
FIGURE 53
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, ame or any other
source of ignition to check for gas leaks.
D-Testing Gas Supply Pressure
An inlet post located on the gas valve provides access to
the supply pressure. See FIGURE 52. 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 28 for supply line pressure.
E-Check Manifold Pressure
A manifold pressure post located on the gas valve pro-
vides access to the manifold pressure. See FIGURE 52.
Back out the 3/32 hex screw one turn, connect a piece
of 5/16 tubing and connect to a manometer to measure
manifold pressure.
To correctly measure manifold pressure, the di󰀨erential
pressure between the positive gas manifold and the neg-
ative burner box must be considered.
IMPORTANT
For safety, connect a shut-o󰀨 valve between the
manometer and the gas tap to permit shut o󰀨 of gas
pressure to the manometer.
The gas valve is factory set and should not require adjust-
ment. All gas valves are factory regulated.
1 - Connect the test gauge positive side “+“ to manifold
pressure tap on gas valve as noted above.
2 - Tee into the gas valve regulator vent hose and
connect to test gauge negative “-”.
3 - Ignite unit on low re and let run for 5 minutes to
allow for steady state conditions.
4 - After allowing unit to stabilize for 5 minutes, record
manifold pressure and compare to value given in
TABLE 28.
5 - If necessary, make adjustments. FIGURE 52 shows
location of high re and low re adjustment screws.
6 - Repeat steps 3, 4 and 5 on high re. See values in
TABLE 28.
7 - Shut unit o󰀨 and remove manometer as soon as an
accurate reading has been obtained.
8 - Start unit and perform leak check. Seal leaks if
found.
F- Proper Gas Flow (Approximate)
Furnace should operate at least 5 minutes before check-
ing gas ow. Determine time in seconds for two revolu-
tions of gas through the meter. (Two revolutions assures
a more accurate time.) Divide by two and compare to time
in TABLE 26. If manifold pressure matches TABLE 26 and
rate is incorrect, check gas orices for proper size and
restriction.