Sears N9MP1125J20B1 General Derating Rules, High Altitude Air Pressure Switch, Changing Orifices

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			FOR THE 80,000 BTUH MODELS
HEATING	VALUE			MEAN ELEVATION FEET ABOVE SEA LEVEL
at ALTITUDE		0 to	2001 to	3001 to	4001 to	5001 to	6001 to	7001 to
BTU/CU,	FT.	2000	3000	4000	5000	6000	7000	8000
2500		10.0	8.9	8.4	10.0	10.0	10.0	10.0
Orifice	Size	#55	#55	#55

NOTE: Propane data		is based		on 1.53 specific gravity. For fuels with different					specific gravity consult the National Fuel Gas Code ANSI Z223.1-2002/N FPA
54-2002 or National		Standard		Of Canada,		Natural	Gas And	Propane Installation Code CSA B149.1-00.
NOTE: The	derating	of	these		furnaces	at 2%	(Natural	Gas) and	Changing Orifices for High Altitude
4% (Propane	Gas)	has	been		tested and	design-certified		by CSA.

General Derating Rules

1, These furnaces may be used at full input rating when installed at altitudes up to 2,000'. When installed above 2,000', the input must be decreased 2% (natural) or 4% (LP) for each 1000' above sea level. See Table 10 for required high altitude input rate.

ELECTRICAL SHOCK, FIRE OR EXPLOSION HAZARD

Failure to properly install orifices could result in death, personal injury and/or property damage.

Turn OFF electric power (at disconnect) and gas supply (at manual valve in gas line) when installing orifices. Installation of orifices requires a qualified service technician.

	High	Altitude	Input Rate		=
Nameplate	Sea	Level	Input	Rate x (Multiplier)
Elevation			High	Altitude	Multiplier
		Natural Gas			LP Gas
2001'-3000'			0.95		0.90
3001'-4000'			0.93		0.86
4001'-5000'			0.91		0.82
5001'-6000'			0.89		0.78
6001'-7000'			0.87		0.74
7001'-8000'			0.85		0.70

NOTE: Main burner orifices can be changed for high altitudes.

1.Disconnect gas line from gas valve.

2.Remove manifold from furnace.

3.Remove the orifices from the manifold and replace them with properly sized orifices.

4.Tighten orifices so it is seated and gas tight. (See Figure 29)

5.Reinstallmanifold. EnsureburnersdoNOTbindonnewori- rices.

Based on mid-range of elevation.

2.For operation with natural gas at altitudes above 2,000', ori-

fice change and/or manifold pressure adjustments may be required for the gas supplied. First consult your local gas supplier, then refer to Table 6 (50,000, 75,000, 100,000 and 125,000 BTU H models) or Table 8 (80,000 BTUH mod- els) for required pressure change and/or orifice change for high altitudes.

3, For operation with LP gas, gas orifices MUST be changed and manifold pressure MUST be maintained as per Table 7

(50,000, 75,000,100,000 and 125,000 BTUH models) or Table 9 (80,000 BTUH models). Orifices can be ordered through our distributor. (See Figure 29)

4.In cases where Table 6, Table 7, Table 8 or Table 9 is not

applicable, eg. alternate input rate application, refer to Table 10 for required high altitude input rate.

Changing Orifices

Measure from face of orifice to the back side of the manifold,

11/8" to 13/16 "

Natural Gas Input Rating Check

NOTE: The gas meter can be used to measure input to furnace. Rating is based on a natural gas BTU content of 1,000 BTU's per cubic meter. Check with gas supplier for actual BTU content.

1.Make sure burner compartment door is in place before per- forming the following steps.

High Altitude Air Pressure Switch

Altitudes over 4,000' may require a different air pressure switch than the one installed at the factory. Check parts list for pressure switch and consult your distributor for part number and availability.

In Canada, provincial codes may govern installation of switch. Check with governing authorities.

2.Turn OFF gas supply to all appliances and start furnace.

Example

BTU Content PerHour Foot in Seconds Hour

1,0003,6004875,000

1,000 x 3,600 ÷ 48 = 75,000 BTUH

44001 102004 E_