Heating System Service Checks - Lennox EL296DFE Series Manual

IV-HEATING SYSTEM SERVICE CHECKS
A-CSA Certification
All units are CSA design certified without modifications.
Refer to the EL296DFE Installation Instruction.
B-Gas Piping
CAUTION
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 51.
If the pressure is greater than 0.5psig (14"W.C.), use the
manual shut-off valve before pressure testing to isolate
furnace from gas supply.
MANUAL MAIN SHUT-OFF
VALVE WILL NOT HOLD
NORMAL TEST PRESSURE
1/8" N.P.T. PLUGGED TAP
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.
CAP
FURNACE
ISOLATE
GAS VALVE
Page 46
Do not use matches, candles, flame or any other
source of ignition to check for gas leaks.
D-Testing Gas Supply Pressure
An inlet pressure 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 24 for supply line pressure.
E-Check Manifold Pressure
NOTE - Pressure test adapter kit (10L34) is available from
Lennox to facilitate manifold pressure measurement.
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 differential
pressure between the positive gas manifold and the neg-
ative burner box must be considered.
IMPORTANT
For safety, connect a shut-off valve between the
manometer and the gas tap to permit shut off of gas
pressure to the manometer.
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 fire and let run for 5 minutes to
allow for steady state conditions.
4 - After allowing unit to stabilize for 5 minutes, record
low fire manifold pressure and compare to value
given in table 24. If necessary, make adjustment.
Figure 52 shows location of low fire adjustment
screw.
5 - Repeat on high fire and compare to value given in
table 24. If necessary, make adjustment. Figure 52
shows location of high fire adjustment screw.
6 - Shut unit off and remove manometer as soon as an
accurate reading has been obtained. Take care to
replace pressure tap plug.
7 - Start unit and perform leak check. Seal leaks if
found.
The gas valve is factory set and should not require adjust-
ment. All gas valves are factory regulated.
F- Proper Gas Flow (Approximate)
Furnace should operate at least 5 minutes before check-
ing gas flow. 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 21 below. If manifold pressure matches table 24
and rate is incorrect, check gas orifices for proper size and
restriction.