Gas Pressure Adjustment - Lennox ELITE Series Installation Instructions Manual

MANIFOLD
INLET PRESSURE POST
PRESSURE POST
GAS VALVE SHOWN IN ON POSITION
FIGURE 31
8 - Move switch on gas valve to ON. Do not force. See fig­
ure 31.
9 - Replace the upper access panel.
10- Turn on all electrical power to to the unit.
11- Set the thermostat to desired setting.
NOTE - When unit is initially started, steps 1 through 11
may need to be repeated to purge air from gas line.
12- If the appliance will not operate, follow the instructions
"Turning Off Gas to Unit" and call your service techni­
cian or gas supplier.
Turning Off Gas to Unit
1 - Set the thermostat to the lowest setting.
2 - Turn off all electrical power to the unit if service is to be
performed.
3 - Remove the upper access panel.
4 - Move switch on gas valve to OFF. Do not force.
5 - Replace the upper access panel.
Failure To Operate
If the unit fails to operate, check the following:
1 - Is the thermostat calling for heat?
2 - Are access panels securely in place?
3 - Is the main disconnect switch closed?
4 - Is there a blown fuse or tripped circuit breaker?
5 - Is the filter dirty or plugged? Dirty or plugged filters will
cause the limit control to shut the unit off.
6 - Is gas turned on at the meter?
7 - Is the manual main shut‐off valve open?
8 - Is the gas valve ON/OFF switch in the ON position?
9 - Is the unit ignition system in lock out? If the unit locks
out again, call the service technician to inspect the unit
for blockages.
10 - Is pressure switch closed? Obstructed flue will cause
unit to shut off at pressure switch. Check flue and outlet
for blockages.
11 - Are flame rollout switches tripped? If flame rollout
switches are tripped, call the service technician for in­
spection.
HIGH FIRE ADJUSTMENT
SCREW
(under cap)
Page 30

Gas Pressure Adjustment

Gas Flow (Approximate)
TABLE 9
GAS METER CLOCKING CHART
Seconds for One Revolution
Natural
EL280UH
Unit
1 cu ft
Dial
-045 80
-070 55
-090 41
-110 33
-135 27
Natural-1000 btu/cu ft
Furnace should operate at least 5 minutes before checking
gas flow. Determine time in seconds for two revolutions of
gas through the meter. (Two revolutions assures a more
accurate time.) Divide by two and compare to time in table
9 below. If manifold pressure matches table 11 and rate is
incorrect, check gas orifices for proper size and restriction.
Remove temporary gas meter if installed.
NOTE - To obtain accurate reading, shut off all other gas
appliances connected to meter.
Supply Pressure Measurement
An inlet post located on the gas valve provides access to
the supply pressure. See figure 31. Back out the 3/32" hex
screw one turn, connect a piece of 5/16" tubing and con­
nect to a manometer to measure supply pressure. See
table 11 for supply line pressure.
Manifold Pressure
A manifold pressure post located on the gas valve provides
access to the manifold pressure. See figure 31. Back out
the 3/32 hex screw one turn, connect a piece of 5/16" tubing
and connect to a manometer to measure manifold pres­
sure.
NOTE - Pressure test adapter kit (10L34) is available from
Lennox to facilitate manifold pressure measurement.
1 - Connect test gauge to manifold pressure post (figure
31) gas valve.
2 - Ignite unit on high fire and let run for 5 minutes to allow
for steady state conditions.
3 - After allowing unit to stabilize for 5 minutes, record
manifold pressure and compare to value given in table
11.
4 - If necessary, make adjustments. Figure 31 shows
location of high fire adjustment screw.
5 - If an adjustment is made on high fire, re-check man­
ifold pressure on low fire. Do not adjust low fire man­
ifold pressure. If low fire manifold pressure is more
than 1/2" above or below value specified in table 11,
replace valve.
NOTE - Shut unit off and remove manometer as soon as an
accurate reading has been obtained. Turn the supply and
manifold 3/32" hex screw one revolution back into the gas
valve.
LP
2 cu ft 1 cu ft 2 cu ft
Dial Dial DIAL
160 200 400
110 136 272
82 102 204
66 82 164
54 68 136
LP-2500 btu/cu ft