Lennox International Inc EL296UHE Gas Pressure Adjustment, GAS Meter Clocking Chart, Dial

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 15-second prepurge, the hot surface ignitor en­ ergizes.

4 - After a 20-second ignitor warm-up period, the gas valve solenoid opens. A 4-second trial for ignition peri­ od 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 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 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 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
-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
	Natural-1000 btu/cu ft			LP-2500 btu/cu ft

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. Re-start unit and check gas valve for gas leaks.

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