Sears N9MP2, N9MP1, 9MPD Alternate Btuh Input RatingsUSA Only, SupplyPressure, Gas Supply Pressure

5. Gas Supply and Piping

CARBON MONOXIDE POISONING, FIRE AND EXPLO- SION HAZARD

Models designated for Natural Gas are to be used with Natural Gas Only, unless properly converted to use with LP gas.

Furnace operating with the wrong fuel result in death,

personal injury and/or property damage.

NOTE: The rating plate is stamped with the model number, gas

type and gas input rating. In addition, models manufactured for sale in Canada have orifice size information stamped on the rat- ing plate.

Alternate BTUH Input Ratings(USA Only)

The input rating of these furnaces can be changed from the stan- dard input rating to the alternate input rating shown in Table 5, by changing the main burner orifices. NOTE: The input rating ot 80,000 BTUH models cannot be changed from the standard in- put. Changing of burner orifices MUST be done by a qualified ser-

vice technician. See section on changing orifices or following page.

Alternate Input Ratings, USA ONLY.

BTUH	BTUH	Natural	LP
Standard	Alternate	Gas	Gas
Rating	Rating	Orifice	Orifice
50,000	40,000	#44	#55
75,000	60,000	#44	#55
100,000	80,000	#44	#55
125,000	100,000	#44	#55

SupplyPressure

FIRE HAZARD

Failure to properly set input pressure can result in

death, personal injury and/or property damage.

Do NOT set input rating above that shown on rating plate.

1, Supply pressure can be checked using the 1/8" NPT port on the supply side of the gas valve.

2.Gas input to burners MUST NOT exceed the rated input shown on rating plate.

3.Do NOT allow minimum gas supply pressure to vary down- ward. Doing so will decrease input to furnace. Refer to Table 6 for normal gas supply and manifold pressures.

	Gas	Pressures		Below	2000'
Gas	Supply	Pressure			Manifold
					Pressure
Type	Recommended	Max.		Min.
Natural	7"	14"		4.5"	3.5"
LP	11"	14"		11"	10"
	Important		Note:

•With Propane gas, the rated input is obtained when the BTU content is 2,500 BTU per cubic foot and manifold pressure set at 10" W.C.

•If Propane gas has a different BTU content, orifices

MUST be changed by licensed Propane installer.

•Measured input can NOT exceed rated input.

•Any major change in gas flow requires changing burn- er orifice size.

Gas Supply Pressure

Gas supply pressure should be within minimum and maximum values listed on rating plate. Pressures are usually set by gas sup- pliers.

Manifold Gas Pressure Adjustment

NOTE: Make adjustment to manifold pressure with burners oper- ating.

FIRE OR EXPLOSION HAZARD

Failure to turn OFF gas at shut off before connecting

manometer can result in death, personal injury and/or

property damage.

Turn OFF gas at shut off before connecting manometer.

1.Remove the burner compartment door.

2.With gas OFF, connect manometer to tapped opening on gas valve. Use manometer with a 0 to 15" water column range.

3.Turn gas ON and remove adjustment screw cover on gas

valve. Turn counterclockwise to decrease pressure and clockwise to increase.

4.For altitudes up to 2000', set pressure to value shown in Table 6, ± 0.3" water column.

5.Connect manometer to the tapped opening on the outlet side of gas valve. Use manometer with a 0-15" min. water column range.

6.Turn gas ON, fire the furnace and remove adjustment screw cover on gas valve.

7.Turn counterclockwise to decrease pressure and clock- wise to increase.

8.SetpressuretovalueshowninTable6. Refertolmportant Notes in Table 6. Pressure is also listed on furnace rating plate.

9.When pressure is set, replace adjustment screw cover on gas valve.

10.Replace the burner compartment door.

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