Lennox International Inc G61MP specifications Testing Gas Supply Pressure, Check Manifold Pressure

When checking piping connections for gas leaks, use pre- ferred means. Kitchen detergents can cause harmful corro- sion on various metals used in gas piping. Use of a specialty Gas Leak Detector is strongly recommended. It is available through Lennox under part number 31B2001. See Corp. 8411−L10, for further details.

Do not use matches, candles, flame or any other source of ignition to check for gas leaks.

D−Testing Gas Supply Pressure

When testing supply gas pressure, connect test gauge to inlet pressure tap on the gas valve. See figures and 35 and

36.Check gas line pressure with unit firing at maximum rate. Low pressure may result in erratic operation or under- fire. High pressure can result in permanent damage to gas valve or overfire. See table 15 for operating pressure at unit gas connection (line).

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 15.

TABLE 15

All G61MP Units	Natural	LP
Line Pressure WC"	4.5 − 10.5	11.0 − 13.0

E−Check Manifold Pressure

After line pressure has been checked and adjusted, check manifold pressure. Move pressure gauge to outlet pres- sure tap located on unit gas valve (GV1). Checks of man- ifold pressure are made as verification of proper regulator ad- justment. Manifold pressure for the G61MP can be measured at any time the gas valve is open and is supplying gas to the unit. See table 19 for manifold pressures.

IMPORTANT

For safety, connect a shut-off valve between the manometer and the gas tap to permit shut off of gas pressure to the manometer.

The gas valve is factory set and should not require adjust- ment. All gas valves are factory regulated sensing atmo- spheric pressure.

Manifold Pressure Measurement & Adjustment NOTE − Pressure test adapter kit (10L34) is available from Lennox to facilitate manifold pressure measurement.

1 − Connect test gauge to outlet tap on gas valve.

2 − Disconnect pressure sensing hose from gas valve.

3 − Start unit on low heat and allow 5 minutes for unit to reach steady state.

4 − While waiting for the unit to stabilize, notice the flame. Flame should be stable and should not lift from burner. Natural gas should burn blue.

5 − After allowing unit to stabilize for 5 minutes, record manifold pressure and compare to value given in table 19.

6 − Repeat steps 3, 4 and 5 on high heat.

NOTE − Shut unit off and remove manometer as soon as an accurate reading has been obtained. Take care to replace pressure tap plug.

NOTE − During this test procedure, the unit will be overfir- ing:

DOperate unit only long enough to obtain accurate read- ing to prevent overheating heat exchanger.

DAttempts to clock gas meter during this procedure will be inaccurate. Measure gas flow rate only during nor- mal unit operation.

7 − When test is complete remove obstruction from hose and return hose to gas valve barbed fitting.

F− Proper Gas Flow (Approximate)

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 16 below. If manifold pressure matches table 15 and rate is incorrect, check gas orifices for proper size and restriction.

NOTE− To obtain accurate reading, shut off all other gas appliances connected to meter.

TABLE 16

GAS METER CLOCKING CHART

	Seconds for One Revolution
G61MP	Natural			LP
Unit	1 cu ft	2 cu ft		1 cu ft	2 cu ft
	Dial	Dial		Dial	DIAL
−45	82	164		205	410
−70	55	110		136	272
−90	41	82		102	204
−110	33	66		82	164
−135	27	54		68	136
Natural−1000 btu/cu ft			LP−2500 btu/cu ft

IMPORTANT

For safety, shut unit off and remove manometer as soon as an accurate reading has been obtained. Take care to replace pressure tap plug.

G− Proper Combustion

Furnace should operate minimum 15 minutes with correct manifold pressure and gas flow rate before checking com- bustion. See sections E− and F−. Take combustion sample beyond the flue outlet and compare to the tables below. The maximum carbon monoxide reading should not ex- ceed 100 ppm.

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