4 - Move gas valve switch to OFF.
5 - Replace the 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 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 opera tion. Switch is factory set and requires no adjustment.
3 - After a
4 - After a
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 igni tion 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 auto matically repeat steps 1 through 6 after 60 minutes.
To interrupt the
Gas Pressure Adjustment
Gas Flow (Approximate)
TABLE 15
GAS METER CLOCKING CHART
|
| Seconds for One Revolution | |||||
|
|
|
|
|
|
|
|
EL296 |
| Natural |
| LP |
| ||
Unit |
| 1 cu ft | 2 cu ft |
| 1 cu ft |
| 2 cu ft |
|
| Dial | Dial |
| Dial |
| DIAL |
|
|
|
|
|
|
|
|
| 80 | 160 |
| 200 |
| 400 | |
|
|
|
|
|
|
|
|
| 55 | 110 |
| 136 |
| 272 | |
|
|
|
|
|
|
|
|
| 41 | 82 |
| 102 |
| 204 | |
|
|
|
|
|
|
|
|
| 33 | 66 |
| 82 |
| 164 | |
|
|
|
|
|
|
|
|
| 27 | 54 |
| 68 |
| 136 | |
|
|
|
|
|
|
|
|
|
| ||||||
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 15. If manifold pressure matches table 17 and rate is incorrect, check gas orifices for proper size and re striction. 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 66. 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 17 for supply line pressure.
On multiple unit installations, each unit should be checked separately, with and without units operating. Supply pres sure must fall within range listed in table 17.
Manifold Pressure Measurement
NOTE - Pressure test adapter kit (10L34) is available from Lennox to facilitate manifold pressure measurement.
A manifold pressure post located on the gas valve provides access to the manifold pressure. See figure 66. 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.
To correctly measure manifold pressure, the differential pressure between the positive gas manifold and the nega tive burner box must be considered.
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 manifold pressure and compare to value given in table 17.
5 - If necessary, make adjustments. Figure 66 shows location of high fire and low fire adjustment screws.
6 - Repeat steps 3, 4 and 5 on high fire. See values in table 17.
NOTE - Shut unit off and remove manometer as soon as an accurate reading has been obtained.
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