Lennox International Inc Elite Series Gas Furnace Upflow/Horizontal Air Discharge High Altitude

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.

Gas Pressure Adjustment

Gas Flow (Approximate)

TABLE 12

GAS METER CLOCKING CHART

	Seconds for One Revolution
EL280UH	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 12 below. If manifold pressure matches table 14 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 34. 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 14 for supply line pressure.

Manifold Pressure

A manifold pressure post located on the gas valve provides

access to the manifold pressure. See figure 34. 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 34) 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 14.

4 − If necessary, make adjustments. Figure 34 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 14, 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.

Proper Combustion

Furnace should operate minimum 15 minutes with correct manifold pressure and gas flow rate before checking com- bustion. Table 13 shows acceptable combustion for ALL EL280UH models. The maximum carbon monoxide reading should not exceed 50 ppm

TABLE 13

Firing Rate	CO2% For Nat	CO2% For L.P.
High Fire	6.8 − 7.4	7.5 − 9.0
Low Fire	4.2 − 5.7	5.0 − 6.0

High Altitude

The manifold pressure may require adjustment and com- bustion air pressure switch may need replacing to ensure proper combustion at higher altitudes. Refer to table 14 for manifold pressure and table 15 for pressure switch change and gas conversion kits.

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