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SERVICE AND TECHNICAL SUPPORT MANUAL

Gas Furnace: N9MSB

Specifications  subject to change without notice.

440 04 4413 00

5

FURNACE DAMAGE HAZARD

Failure to follow this caution may result in reduced furnace

life.
DO NOT redrill orifices. Improper drilling (burrs,

out

of

round holes, etc.) can cause excessive burner

noise and misdirection of burner flames. This can result in

flame impingement of heat exchangers, causing failures.

(See 

Figure 2

)

CAUTION

!

Figure 2

Orifice Hole

A93059

BURNER

ORIFICE

For proper operation and long term reliability the furnace input

rate must be /

2  percent of input rate on furnace rating

plate, or as adjusted for altitude.
The gas input rate on rating plate is for installation at altitudes

up to 2000 ft. (610 M)

NOTICE

The NATURAL GAS manifold pressure adjustments in 

Table 3

compensate for BOTH altitude AND gas heating value. DO

NOT apply an additional de

rate factor to the pressures shown

in 

Table 3

. The values in this Table and NOT referenced to sea

level; they are AS

MEASURED AT ALTITUDE.

The heating content of natural gas at altitude may already

provide for a reduction in capacity or altitude. Refer to 

Table 3

.

No adjustments to the furnace may be necessary at altitude for

certain gas heating values.
Refer to the instructions provided in the factory-specified

Propane conversion kit for instructions for setting gas manifold

pressures for Propane applications.

In the USA, the input rating for altitudes above 2000 ft. (610 M)

must be reduced by 2 percent for each 1000 ft. (305 M) above

sea level refer to 

Table 1

. The natural gas manifold pressures

in 

Table 3

 adjust for BOTH altitude and natural gas heating

value.
In Canada, the input rating must be reduced by 5 percent for

altitudes of 2000 ft. to 4500 ft. (610 to 1372 M) above sea level.

The natural gas manifold pressures in 

Table 3

 adjust for BOTH

altitude and natural gas heating value.

NOTE

:  For Canadian altitudes of 2000 to 4500 ft. (610 to 1372

M), use USA altitudes of 2001 to 3000 ft. (611 to 914 M) in

Table 3

.

To adjust manifold pressure to obtain the proper input rate, first,

determine if the furnace has the correct orifice installed. At

higher altitudes or different gas heat contents, it may be

necessary to change the factory orifice to a different orifice.

Tables have been provided in the furnace Service and

Technical Manual to match the required orifice to the manifold

pressure to the heat content and specific gravity of the gas. To

do this:

1. Obtain average yearly gas heat value (at installed

altitude) from local gas supplier.

2. Obtain average yearly gas specific gravity from local gas

supplier.

3. Find installation altitude range for your installation in the

manifold pressure tables in 

Table 3

.

4. Find closest natural gas heat value and specific gravity in

Table 3

. Follow heat value and specific gravity lines to

point of intersection to find orifice size and low-and

high-heat manifold pressure settings for proper

operation.

5. Check and verify burner orifice size in furnace. NEVER

ASSUME ORIFICE SIZE. ALWAYS CHECK AND

VERIFY.

NOTICE

If orifice hole appears damaged or it is suspected to have been

redrilled, check orifice hole with a numbered drill bit of correct

size. Never redrill an orifice. A burr

free and squarely aligned

orifice hole is essential for proper flame characteristics.

6. Replace orifice with correct size, if required by 

Table 3

.

Use only factory

supplied orifices. See EXAMPLE 1.

EXAMPLE 1:

0 - 2000 ft. (0 - 609.6M) altitude

Heating value = 1050 Btu/cu ft.

Specific gravity = 0.62

Therefore: Orifice No. 44

(Furnace is shipped with No. 44 orifices. In this example, all

main burner orifices are the correct size and do not need to be

changed to obtain proper input rate.)

Manifold pressure: 3.4-in. w.c. (847 Pa).

NOTE

:  To convert gas manifold Table pressures to Pascals,

multiply the in.w.c. value by 249.1 Pa/in. w.c. (1 in. wc. = 249.1
Pa).

Table 1

Altitude Derate Multiplier for USA

ALTITUDE

FT. (M)

PERCENT

OF DERATE

DERATE MULTIPLIER

FACTOR*

0–2000

(0

610)

0

1.00

2001–3000

(610

914)

4

6

0.95

3001–4000

(914

1219)

6

8

0.93

4001–5000

(1219

1524)

8

10

0.91

5001–6000

(1524

1829)

10

12

0.89

6001–7000

(1829

2134)

12

14

0.87

7001–8000

(2134

2438)

14

16

0.85

8001–9000

(2438

2743)

16

18

0.83

9001–10,000

(2743

3048)

18

20

0.81

* Derate multiplier factors are based on midpoint altitude for altitude range.

NOTE

:  

For Canadian altitudes of 2000 to 4500 ft. (610 to

1372 M), use USA altitudes of 2001 to 3000 ft. (610 to 914
M)

Summary of Contents for N9MSB0401410C

Page 1: ...The signal word WARNING is used throughout this manual in the following manner Safety alert symbol When you see this symbol on the unit and in instructions or manuals be alert to the potential for pe...

Page 2: ...eath WARNING signifies hazards which could result in personal injury or death CAUTION is used to identify unsafe practices which may result in minor personal injury or product and property damage NOTE...

Page 3: ...am of Furnace Drip Leg Gas Valve turned ON Type of Gas Natural Propane Filter Type and Size Check in box the Blower OFF Delay Jumper Heating Position for Fan Time OFF Setting 1 and 2 2 and 3 3 and 4 5...

Page 4: ...is energized whenever blower operates HUM 24vac terminal is only energized the draft inducer is energized in heating Prime Condensate Trap with Water CARBON MONOXIDE POISONING HAZARD Failure to follo...

Page 5: ...has the correct orifice installed At higher altitudes or different gas heat contents it may be necessary to change the factory orifice to a different orifice Tables have been provided in the furnace S...

Page 6: ...rewdriver counterclockwise out to decrease input rate or clockwise in to increase input rate NOTICE DO NOT set low heat manifold pressure less than 2 8 in w c 697 Pa or more than 3 8 in w c 947 Pa for...

Page 7: ...24 VAC CONNECTIONS P2 HOT SURFACE IGNITOR HSI INDUCER MOTOR IND CONNECTOR 115 VAC L1 LINE VOLTAGE CONNECTION SPARE1 COM BLUE 115 VAC L2 NEUTRAL CONNECTIONS 24 V THERMOSTAT TERMINALS HUMIDIFIER TERMINA...

Page 8: ...300 21 171 343 857 62 58 116 290 22 164 327 818 64 56 112 281 23 157 313 783 66 54 109 273 24 150 300 750 68 53 106 265 25 144 288 720 70 51 103 257 26 138 277 692 72 50 100 250 27 133 267 667 74 48 9...

Page 9: ...42 3 4 42 3 5 42 3 6 3001 800 43 3 8 42 3 2 42 3 3 42 3 4 915 825 43 3 6 43 3 7 43 3 8 42 3 2 850 44 3 8 43 3 5 43 3 6 43 3 7 875 44 3 6 44 3 7 43 3 4 43 3 5 4000 900 44 3 4 44 3 5 44 3 7 44 3 8 1219...

Page 10: ...ding Leaving blower door off will result in incorrect temperature measurements due to possible changes in duct static pressure and airflow FURNACE DAMAGE HAZARD Failure to follow this caution may resu...

Page 11: ...e terminals R and W The thermostat anticipator should NOT be in the circuit while measuring current 1 Remove thermostat from sub base or from wall 2 Connect an amp meter across the R and W sub base te...

Page 12: ...2 5 394 1030 1025 1030 1010 985 940 905 855 805 735 801716C SIDE BOTTOM Black 4 0 389 1650 1620 1640 1605 1555 1495 1425 1345 1255 1165 Yellow 3 5 381 1420 1425 1400 1370 1335 1290 1230 1170 1095 1015...

Page 13: ...nominal break point of each switch is shown on the label below the reference location in inches of water column W C The maximum and minimum break point of the switch is 0 05 inches of water column fro...

Page 14: ...LED 6 A component test sequence will follow 7 Reinstall the Main Control door Component Self Test NOTE The furnace control component test allows all components to run for a short time except the gas v...

Page 15: ...rvice as necessary 4 Inspect burner compartment before each heating season for rust corrosion soot or excessive dust If necessary have furnace and burner serviced by a qualified service agency 5 Inspe...

Page 16: ...t on blower wheel remove wheel from the blower housing and wash it with an appropriate degreaser To remove wheel a Mark blower wheel location on shaft before disassembly to ensure proper reassembly b...

Page 17: ...old or damaging the mounting to the burner assembly ELECTRICAL SHOCK AND FIRE HAZARD Failure to follow this warning could result in personal injury death and or property damage Turn off the gas and el...

Page 18: ...ck for proper operation 18 Install control door when complete Servicing Hot Surface Igniter The igniter does NOT require annual inspection Check igniter resistance before removal Refer to Figure 9 Fig...

Page 19: ...6 Connect condensate drain elbow or drain extension elbow to the condensate trap 7 Connect the leads of the condensate heat pad if used 8 Connect external drain piping to the condensate drain elbow or...

Page 20: ...ratures may be 32_ F 0_ C or lower freeze protection measures must be taken to prevent property or product damage CAUTION Since the furnace uses a condensing heat exchanger some water will accumulate...

Page 21: ...SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace N9MSB Specifications subject to change without notice 440 04 4413 00 21 Figure 14 Service Label 338310 2 Rev F...

Page 22: ...SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace N9MSB Specifications subject to change without notice 22 440 04 4413 00 Figure 15 Wiring Diagram 339241 2 Rev A...

Page 23: ...quence Gas valve and humidifier will not be turned on Inducer motor will start and remain on until the end of the blower test then off The following components are on for 10 15 seconds each individual...

Page 24: ...onent test Does the igniter glow orange white by the end of the 15 second warm up period Unplug igniter harness from control and repeat component test Check for 115V between connector P2 HSI and NEUTR...

Page 25: ...ds after the gas valve GV is energized Simultaneously the electronic air cleaner terminal EAC is energized and remains energized as long as the blower motor BLWM is energized f Heat Off Delay When the...

Page 26: ...ctor box Condensate trap Condensate trap elbow Gaskets WARNING FIRE EXPLOSION ELECTRICAL SHOCK AND CARBON MONOXIDE POISONING HAZARD Failure to follow this warning could result in dangerous operation p...

Page 27: ...ble Speed X ECM S Single stage T Two stage FEATURE B Base AFUE Efficiency E Extra AFUE Efficiency C Communicating D Dual Certified 2 pipe or 1 pipe R 2 pipe only S Single stage T Two stage N Standard...

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