Lennox EL280UH110P60C - Gas Pressure Adjustment

Page 30
GAS VALVE SHOWN IN ON POSITION
INLET PRESSURE POST
HIGH FIRE ADJUSTMENT
SCREW
(under cap)
MANIFOLD
PRESSURE TAP
WHITE RODGERS GAS VALVE
FIGURE 31
8 - Move switch on gas valve to ON. Do not force. See
gure 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 technician 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 lter dirty or plugged? Dirty or plugged lters
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 ue will
cause unit to shut off at pressure switch. Check ue
and outlet for blockages.
11 - Are ame rollout switches tripped? If ame rollout
switches are tripped, call the service technician for
inspection.
Gas Pressure Adjustment
Gas Flow (Approximate)
TABLE 9
GAS METERING CLOCKING CHART
EL280
Unit
Natural 1000 btu/cu ft LP 2500 btu cu/cu ft
Seconds For One Revolution
1 cu ft dial 2 cu fr dial 1 cu ft Dial 2 cu ft Dial
-045 80 160 200 400
-070 55 110 136 272
-090 41 82 102 204
-110 33 66 82 164
-135 27 54 68 136
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 9 below. If manifold pressure matches table 11
and rate is incorrect, check gas orices 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 gure 31. 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 11 for supply line pressure.
Manifold Pressure
A manifold pressure post located on the gas valve pro-
vides access to the manifold pressure. See gure 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 pressure.
NOTE - Pressure test adapter kit (10L34) is available from
Lennox to facilitate manifold pressure measurement.
1 - Connect test gauge to manifold pressure post
(gure 31) gas valve.
2 - Ignite unit on high re 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 re adjustment screw.
5 - If an adjustment is made on high re, re-check
manifold pressure on low re. Do not adjust low re
manifold pressure. If low re manifold pressure is
more than 1/2” above or below value specied in
table 11, replace valve.
6 - soon as an accurate reading has been obtained.
Turn the supply and manifold 3/32” hex screw one
revolution back into the gas valve.
7 - Start unit and perform leak check. Seal leaks if
found.