Gas Pressure Measurement - Lennox ELITE Series Installation Instructions Manual

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 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 internal manual shut-off valve open?
9 - Is the unit ignition system in lockout? If the unit locks
out again, inspect the unit for blockages.
Heating Sequence Of Operation
1 - When thermostat calls for heat, combustion air
inducer starts.
2 - Combustion air pressure switch proves blower
operation. Switch is factory-set and requires no
adjustment.
3 - After a 15-second prepurge, the hot surface ignitor
energizes.
4 - After a 20-second ignitor warm-up period, the gas
valve solenoid opens. A 4-second Trial for Ignition
period begins."
5 - Gas is ignited, flame sensor proves the flame, and
the combustion process continues.
6 - If flame is not detected after first ignition trial, the
ignition control will repeat steps 3 and 4 four
more times before locking out the gas valve
("WATCHGUARD" flame failure mode). The ignition
control will then automatically repeat steps 1 through
6 after 60 minutes. To interrupt the 60-minute
"WATCHGUARD" period, move thermostat from
"Heat" to "OFF" then back to "Heat". Heating
sequence then restarts at step 1.
Gas Pressure Adjustment
(Gas Flow (Approximate)
TABLE 14
GAS METER CLOCKING CHART
Seconds For One Revolution
EL196 Natuarl
Unit
1 cu ft
Dial
-045 80
-070 55
-090 41
Natural-1000 btu/cu ft LP-2500 btu/cu ft
NOTE - To obtain accurate reading, shut off all other gas
appliances connected to meter.
LP/Propane
2 cu ft 1 cu ft 2 cu ft
Dial Dial Dial
160 200 400
110 136 272
82 102 204
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 14. If manifold pressure matches table 15 and rate is
incorrect, check gas orifices for proper size and restriction.
Remove temporary gas meter if installed.
Supply Pressure Measurement
A threaded plug on the inlet side of the gas valve provides
access to the supply pressure tap. Remove the threaded
plug, install a field-provided barbed fitting and connect a
manometer to measure supply pressure. See table 15 for
proper supply line pressure. Replace the threaded plug
after measurements have been taken.
Supply Line and Manifold Pressure (inches w.c.)
Unit
All
All LP/Propane
Check Manifold Pressure
After supply pressure has been checked and adjusted,
check manifold pressure. Move pressure gauge to outlet
pressure tap located on unit gas valve (GV1). Checks of
manifold pressure are made as verification of proper reg-
ulator adjustment.
For safety, connect a shut-off valve between the
manometer and the gas tap to permit shut off of gas
pressure to the manometer.
Follow the steps below. Gas manifold Kit 10L34 provides
additional components if needed.
1 - Connect the test gauge positive side "+" to manifold
pressure tap on gas valve.
2 - Tee into the gas valve regulator vent hose and
connect to test gauge negative "-".
3 - Start unit 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 15.
5 - Shut unit off and remove manometer as soon as an
accurate reading has been obtained. Take care to
replace pressure tap plug.
6 - Start unit and perform leak check. Seal leaks if found.
Page 40
TABLE 15
Manifold
Fuel
Pressure
Nat 3.5
10.0
IMPORTANT
Line Pressure
4.5 - 10.5
11.0 - 13.0