International comfort products N9mp1 User manual

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MULTI POSITION

90% SINGLE STAGE

GAS FURNACES

Part Number

440 08 2011 00

N9MP1, N9MP2 & *9MPD

* Denotes brand H, C, T

Manufactured by:

This manual supports single stage “C” series and later condensing gas furnaces

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

2/2006

N9MP1 −Indoor combustion air (1 pipe only)

N9MP2 −Direct Vent ONLY (2 pipe only)

*9MPD −Dual Certified Venting (1 or 2 pipes)

* Denotes Brand (T, C or H)

Service Manual

Single Stage Multi Position Furnace

TABLE OF CONTENTS

1. INTRODUCTION 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2. UNIT IDENTIFICATION 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3. FURNACE THEORY OF OPERATION 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4. ELECTRICAL SUPPLY 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5. INTERLOCK SWITCH 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6. GAS SUPPLY 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7. L.P. PRESSURE SWITCH 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8. HONEYWELL VR8205S GAS VALVE 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9. HIGH ALTITUDE OPERATION 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10. CHECKING TEMPERATURE RISE 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11. ROOM THERMOSTATS 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12. CONTROL WIRING 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13. TWINNING KITS 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

14. LIMIT SWITCHES 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15. PRESSURE SWITCHES 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16. HIGHER/LOWER NEGATIVE PRESSURES 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

17. VENT/COMBUSTION AIR PIPING 17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

18. STANDARD VENT TERMINATION 17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

19. CONCENTRIC VENT TERMINATION 21. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

20. COMBUSTION BLOWER 22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

21. CONDENSATE DRAIN TRAP 23. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

22. SEQUENCE OF OPERATION 24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

23. CHECKING FLAME CURRENT 26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

24. CAPACITORS 26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

25. BLOWER ASSEMBLY 26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

BLOWER PERFORMANCE DATA 29. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

WIRING DIAGRAM 30. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

TECHNICAL SERVICE DATA (N9MP1 C1) 31. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

TECHNICAL SERVICE DATA (N9MP2 C1) 32. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

TECHNICAL SERVICE DATA (*9MPD C1) 33. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

TROUBLE SHOOTING GUIDE 34. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

DIAGNOSTIC CODE SECTION 35. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

TROUBLE SHOOTING CHART #1 36. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

TROUBLE SHOOTING CHART #2 37. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

TROUBLE SHOOTING CHART #3 38. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

INDEX 40. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Single Stage Multi Position Furnace

Service Manual

440 08 2011 00

INTRODUCTION

This service manual is designed to be used in conjunction

with the installation manual and/or technical support manu-

al provided with each furnace.

These furnaces represent the very latest in high efficiency

gas furnace technology. Consequently, they incorporate

the use of certain controls that contain highly sophisticated

electronic components which are not user serviceable.

Therefore, it is essential that only competent, qualified, ser-

vice personnel attempt to install, service, or maintain this

product.

This Service manual was written to assist the professional

HVAC service technician to quickly and accurately diag-

nose and repair any malfunction of this product.

This service manual covers the following models;

*9MPD−−−−−−C or later, *9MP1 −−−−−−C or

later and *9MP2 −−−−−−C or later models. The overall

operation of all of these models is essentially the same.

This manual, therefore, will deal with all subjects in a gener-

al nature (I.E. all text will pertain to all models) unless that

subject is unique to a particular model or family, in which

case it will be so indicated.

It will be necessary then for you to accurately identify the

unit you are servicing, so you may be certain of a proper

diagnosis and repair. (See Unit Identification, Page 3)

SAFETY REQUIREMENTS

Recognize safety information. This is the safety−alert symbol . When you see this symbol on the furnace and in instructions manuals be alert to

the potential for personal injury.

Understand the signal words DANGER, WARNING, or CAUTION. These words are used with the safety−alert symbol. DANGER identifies the most

serious hazards, those that will result in severe personal injury or death. WARNING signifies a hazard that could result in personal injury or death.

CAUTION is used to identify unsafe practices that could result in minor personal injury or product and property damage. NOTE is used to highlight

suggestions that will result in enhanced installation, reliability, or operation.

Installing and servicing heating equipment can be hazardous due to gas and electrical components. Only trained and qualified personnel should

install, repair, or service heating equipment.

Untrained service personnel can perform basic maintenance functions such as cleaning and replacing air filters. All other operations must be per-

formed by trained service personnel. When working on heating equipment, observe precautions in the literature, on tags, and on labels attached to or

shipped with the unit and other safety precautions that may apply.

Follow all safety codes. In the United States, follow all safety codes including the current edition National Fuel Gas Code (NFGC) ANSI

Z223.1−2002/NFPA No. 54−2002. In Canada, refer to the current edition of the National Standard of Canada Natural Gas and Propane Installation

Code (NSCNGPIC) CSA B149.1−05. Wear safety glasses and work gloves. Have fire extinguisher available during start−up and adjustment proce-

dures and service calls.

These instructions cover minimum requirements and conform to existing national standards and safety codes. In some instances, these instructions

exceed certain local codes and ordinances, especially those that may not have kept up with changing residential construction practices. We require

these instructions as a minimum for a safe installation.

cInternational Comfort Products LLC

Lewisburg, TN 37091

Single Stage Multi Position Furnace Service Manual

440 08 2011 00 5

UNIT IDENTIFICATION

The unit’s rating plate contains important information for the

service technician. It also lists the complete Model

Manufacturing and Serial Numbers.

These complete numbers are required to obtain correct re-

placement parts (example, in certain model families a unit

having a MARKETING REVISION of “C” is likely to be

equipped with one or more different components.

MODEL NUMBER IDENTIFICATION GUIDE

* 9M P D0 75 B1 2 C 1

Brand Identifier Engineering Rev.

T = Tempstar Denotes major changes

C = Comfortmaker Marketing Digit

H = Heil Denotes major change

A = Arcoaire

N = Non−Brand Specific (Generic) Cooling Airflow

Brand Identifier 08 = 800 CFM

8 = Non−Condensing, 80+% Gas Furnace 12 = 1200 CFM

9 = Condensing, 90+% Gas Furnace 14 = 1400 CFM

Installation Configuration 16 = 1600 CFM

UP = Upflow DN = Downflow UH = Upflow/Horizontal 20 = 2000 CFM

HZ = Horizontal DH = Downflow/Horizontal

MP = Multiposition, Upflow/Downflow/Horizontal Cabinet Width

Major Design Feature B = 15.5″Wide

1 = One (Single) Pipe N = Single Stage F = 19.1″Wide

2 = Two Pipe P = PVC Vent J = 22.8″Wide

D = 1 or 2 Pipe T = Two Stage L = 24.5″Wide

L = Low NOx V = Variable Speed Input (Nominal MBTUH)

FURNACE THEORY OF OPERATION

The high efficiencies and lower profile (compared to past

series) of this furnace have been obtained using design

techniques not typical of traditional furnace designs. A brief

description of these new design techniques and the pur-

pose they serve follows.

1. Reducing the height of the furnace while maintaining

the high efficiency of pervious models required main-

taining the surface area of the heat exchanger and

yet minimizing the overall size.

The design required to achieve these results is the “SER-

PENTINE” design, wherein the flue gasses must follow a

serpent shaped passage through the heat exchanger via

convection.

This “Serpentine” path is resistive to normal convective

flow, and requires that a partial vacuum be created at the

outlet of the heat exchanger to maintain the flow of flue

products through the heat exchanger.

2. The serpentine heat exchanger design does not lend

itself well to the ribbon type, or slotted port type burner

found in more traditional design furnaces for the fol-

lowing reasons:

A. The secondary combustion airflows at right angles

to the burner flame, making it likely to “pull” the

flame off a ribbon or slotted port type burner.

B. The flame “height” of a ribbon or slotted port type

burner would make it difficult (if not impossible) to

prevent impingement of the flame on the heat ex-

changer surfaces whole maintaining the low profile

heat exchanger.

For these reasons, an “INSHOT” type burner is used in this

series. The inshot burner (also called a “jet” burner) fires a

flame straight out its end. This burner is designed to fire into

a tube style heat exchanger, making it an ideal application

in the tube−like passages of the serpentine heat exchanger.

3. In order to extract the maximum amount of heat pos-

sible from the flue gasses, a secondary heat ex-

changer (condenser) is connected to the outlet of the

primary heat exchanger. This condenser removes

additional heat from the flue gasses, causing their

temperature to drop below dew point. This results in

the forming of condensation (water) which then must

be routed to a drain.

4. The placement of the secondary heat exchanger at

the outlet of the primary heat exchanger creates addi-

tional resistance to the flow of gasses.

5. To overcome the resistance to convective flow of the

Primary and Secondary heat exchangers requires the

use of an Induced Draft Combustion Blower Assem-

bly.

Single Stage Multi Position Furnace

Service Manual

440 08 2011 00

6. The Combustion Blower Assembly is mounted on the

outlet side of the Secondary heat exchanger, This

blower creates a partial vacuum (negative pressure)

within the heat exchangers drawing the flue products

out of the furnace.

7. A pressure switch (Air Proving Switch) is used as a

safety device that prevents the ignition system from

firing the furnace until it senses that a proper draft has

been established through the furnace.

SEQUENCE OF OPERATION − HEATING

Refer to the ignition control section for sequence of opera-

tion.

ELECTRICAL SUPPLY

ELECTRICAL SHOCK HAZARD.

Failure to turn off power could result in death or

personal injury.

Turn OFF electrical power at fuse box or service

panel before making any electrical connections

and ensure a proper ground connection is made

before connecting line voltage.

!WARNING

SUPPLY CIRCUIT

The furnace cannot be expected to operate correctly unless

it is properly connected (wired) to an adequately sized

single branch circuit. Line voltage wires should conform to

temperature limitation of 63°F (35°C) rise and be sized for

the unit maximum amps stated on the rating plate. Add the

full load amps for potential field −installed accessories that

would receive power from the furnace control. Consult NEC

or local codes for proper wire and circuit sizing.

SUPPLY VOLTAGE

Supply voltage to the furnace should be a nominal 115 volts.

It MUST be between 104 volts and 127 volts. Supply volt-

age to the furnace should be checked WITH THE FUR-

NACE IN OPERATION. Voltage readings outside the speci-

fied range can be expected to cause operating problems.

Their cause MUST be investigated and corrected.

ELECTRICAL GROUND

Proper grounding of the electrical supply to THE FURNACE

IS REQUIRED for safety and operational reasons.

POLARITY

CORRECT POLARITY of the line voltage supply to the fur-

nace is also required for safety and operational reasons.

The furnace control MUST have proper line voltage polarity

to operate properly.

NOTE: Junction Box can be

mounted to either the left or right

side.

25−24−90−2

Models may

have 1 or 2

pressure

switches

NOTE: 115 VAC/60Hz/single−phase

Operating voltage range*: 127 VAC max, 104 VAC min.

* Permissible limits of voltage at which unit will operate satisfactorily

115V. 60 Hz

Low Voltage

Terminal Board

Ground

Connection

Box

HOT

NEUT.

Figure 1 Electrical Connections

CHECKING GROUNDING AND POLARITY

Grounding may be verified as follows:

1. Turn the power supply “OFF”.

2. Using an Ohmmeter check for continuity between the

Neutral (white) wire and Ground wire (green) of the

supply circuit.

3. With the Ohmmeter set on the R x 1 scale, the read-

ing should be zero Ohms.

4. A zero Ohm reading indicates that the neutral is

grounded back to the main panel.

Single Stage Multi Position Furnace Service Manual

440 08 2011 00 7

5. An alternate check would be to check for continuity

from the Neutral to a cold water pipe, (Pipe must be

metal, and must have a continuous, uninterrupted

connection to ground) or to a continuous, uninter-

rupted connection to ground) or to a driven ground

rod.

6. Any readings other than zero Ohms would indicate

a poor ground, or no ground.

Polarity may be verified as follows:

1. Turn the power supply “ON”.

2. Using a Voltmeter check for voltage between the Hot

(Black) and Neutral (White) wire of supply circuit.

3. Reading should be Line (Supply) Voltage.

4. Check for Voltage between the Neutral (White) wire

and Ground wire of the supply circuit.

5. Reading should be zero Volts. (if line voltage is read,

polarity is reversed)

6. A zero Volt reading indicates there is no voltage po-

tential on Neutral wire.

7. Double check by checking for voltage between the

Hot (Black) wire and Ground wire of the supply cir-

cuit.

8. Reading should be Line (supply) Voltage. (if zero

volts is read, there is no ground, or polarity is re-

versed.)

INTERLOCK SWITCH

The blower compartment door of all models is equipped

with an interlock switch. (See Figure 2) This switch is “Nor-

mally Open” (closes when the door is on the furnace) and

interrupts furnace operation when the door is open. This in-

terlock switch is a safety device, and SHOULD NEVER BE

BY−PASSED.

Since this is a single pole switch, (breaking only one side of

the line) proper line polarity is essential to insure that fur-

nace components are not “HOT” when switch is open. (See

Checking Grounding and Polarity)

Figure 2 Typical Interlock Switch

10−12−96

GAS SUPPLY

An adequately sized gas supply to the furnace is required

for proper operation. Gas piping which is undersized will not

provide sufficient capacity for proper operation. Piping

should be sized in accordance with accepted industry stan-

dards. Refer to NFGC and ANSI Z223.1 for proper gas pipe

size.

NATURAL GAS

Inlet (Supply) pressure to the furnace should be checked (at

the gas valve) with ALL OTHER GAS FIRED APPLIANCES

OPERATING. Inlet (Supply) pressure to the furnace under

these conditions MUST be within minimum and maximum

values listed on rating plate. If the inlet pressure is less, it

may be an indication of undersized piping or regulator prob-

lems.

L.P. GAS

Inlet (Supply) pressure to the furnace should be checked in

the same manner as for Natural Gas, however with L.P.

Gas, the inlet pressure MUST be a minimum of 11″W.C. If

this cannot be obtained, problems are indicated in either the

regulator or pipe sizing.

CHECKING INPUT (FIRING) RATE

Once it has been determined that the gas supply is correct

to the furnace, it is necessary to check the input (firing) rate.

This can be done in two (2) ways. First by checking and ad-

justing (as necessary) the manifold (Outlet) pressure. The

second way is to “Clock” the gas meter.

FIRE OR EXPLOSION HAZARD.

Turn OFF gas at shut off before connecting

manometer.

Failure to turn OFF gas at shut off before

connecting manometer can result in death,

personal injury and/or property damage.

Single Stage Multi Position Furnace

Service Manual

440 08 2011 00

Gas Pressure Testing Devices

Figure 3

MAGNEHELIC

MAX. PRESSURE 15 PSIG

510

INCHES OF WATER

Pressure Connections

Typical U" Tube

Manometer

CHECKING MANIFOLD PRESSURE

NOTE: Make adjustment to manifold pressure with burners

operating.

1. Remove the burner compartment door.

2. With gas OFF, connect manometer to outlet tapped

opening on gas valve. Use manometer with a 0 to 15″

water column range.

3. Turn gas on. Remove the blower compartment door.

Operate the furnace by jumpering Rto Won the fur-

nace control board.

4. Remove manifold pressure adjustment screw cover

on furnace gas control valve. Turn adjusting screw

counterclockwise to decrease manifold pressure and

clockwise to increase pressure.

25−24−98a

HONEYWELL

OFF

Typical Gas Control Valve Honeywell

Figure 4

Manifold Regulator

Adjustment

Under Cap

Inlet

Pressure

Tap 1/8NPT

INLET

OUTLET

Outlet

Pressure

Tap

1/8NPT

NOTE: Adjustment screw cover MUST be replaced on gas

control valve before reading manifold pressure and operat-

ing furnace.

5. Obtain gas heating value and installation site altitude.

6. Set manifold pressure to value shown in Table 2,

Table 3, Table 4 or Table 5.

7. When the manifold pressure is properly set, replace

the adjustment screw cover on the gas control valve.

8. Remove jumper wire from thermostat connection on

furnace control board. Remove manometer connec-

tion from manifold pressure tap, and replace plug in

valve.

9. Check for leaks at plug.

10. Replace the burner compartment and blower

compartment door.

Natural Gas Input Rating Check

NOTE: The gas meter can be used to measure input to fur-

nace. Rating is based on a natural gas BTU content of 1,000

BTU’s per cubic foot. Check with gas supplier for actual

BTU content.

1. Make sure burner compartment door is in place be-

fore performing the following steps.

2. Turn OFF gas supply to all appliances and start fur-

nace.

Example

Natural Gas

BTU Content

No. of Seconds

Per Hour

Time Per Cubic

Foot in Seconds

BTU Per

Hour

1,000 3,600 48 75,000

1,000 x 3,600 ÷48 = 75,000 BTUH

3. Time how many seconds it takes the smallest (nor-

mally 1 cfh) dial on the gas meter to make one com-

plete revolution. Refer to Example.

4. Relight all appliances and ensure all pilots are operat-

ing.

NOTE: If meter uses a 2 cubic foot dial, divide results (sec-

onds) by two.

Alternate BTUH Input Ratings (USA Only)

The input rating of these furnaces can be changed from the

standard input rating to the alternate input rating shown in

Table 1, by changing the main burner orifices. Changing of

burner orifices MUST be done by a qualified service techni-

cian. See section on changing orifices on page 9.

Table 1 Alternate Input Ratings, USA ONLY.

BTUH

Standard

Rating

BTUH

Alternate

Rating

Natural

Gas

Orifice*

Gas

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

* See Table 4 for High Altitude.

** See Table 5 for High Altitude

Single Stage Multi Position Furnace Service Manual

440 08 2011 00 9

MANIFOLD PRESSURE AND ORIFICE SIZE FOR HIGH ALTITUDE APPLICATIONS

Table 2 NATURAL GAS MANIFOLD PRESSURE ( w.c.)

MEAN ELEVATION FEET ABOVE SEA LEVEL

HEATING

VALUE

at ALTITUDE

BTU/CU. FT.

0 to

2000

2001 to

3000

3001 to

4000

4001 to

5000

5001 to

6000

6001 to

7000

7001 to

8000

Orifice

No.

Manifold

Pressure

Orifice

No.

Manifold

Pressure

Orifice

No.

Manifold

Pressure

Orifice

No.

Manifold

Pressure

Orifice

No.

Manifold

Pressure

Orifice

No.

Manifold

Pressure

Orifice

No.

Manifold

Pressure

700 −− −− −− −− −− −− −− −− −− −− −− −− 41 3.7

725 −− −− −− −− −− −− −− −− −− −− 41 3.7 41 3.4

750 −− −− −− −− −− −− −− −− −− −− 41 3.5 42 3.6

775 −− −− −− −− −− −− −− −− 41 3.6 42 3.6 42 3.3

800 −− −− −− −− −− −− 41 3.6 42 3.7 42 3.4 42 3.1

825 −− −− −− −− 41 3.7 41 3.4 42 3.5 42 3.2 42 2.9

850 −− −− −− −− 41 3.5 42 3.6 42 3.3 42 3.0 42 2.8

875 −− −− 41 3.6 42 3.6 42 3.4 42 3.1 42 2.8 42 2.6

900 −− −− 42 3.7 42 3.4 42 3.2 42 2.9 42 2.7 42 2.5

925 41 3.7 42 3.5 42 3.3 42 3.0 42 2.8 42 2.5 44 3.3

950 41 3.5 42 3.3 42 3.1 42 2.9 42 2.6 42 2.4 44 3.1

975 42 3.7 42 3.2 42 2.9 42 2.7 42 2.5 44 3.2 45 3.6

1000 42 3.5 42 3.0 42 2.8 42 2.6 42 2.4 45 3.7 45 3.4

1050 42 3.2 42 2.7 42 2.5 44 3.3 45 3.6 −− −− −− −−

1100 43 3.6 42 2.5 44 3.2 45 3.6 −− −− −− −− −− −−

NOTE: Natural gas data is based on 0.60 specific gravity. For fuels with different specific gravity consult the National Fuel Gas Code ANSI

Z223.1−2002/NFPA 54−2002 or National Standard of Canada, Natural Gas And Propane Installation Code CSA B149.1−05.

Bold indicated the factory shipped orifice size #42.

Table 3 LPG or PROPANE GAS MANIFOLD PRESSURE ( w.c.)

FOR THE 90% 80,000 BTUH MODEL AND ALTERNATE INPUT RATINGS

HEATING VALUE

at ALTITUDE

BTU/CU. FT.

MEAN ELEVATION FEET ABOVE SEA LEVEL

0 to

2000

2001 to

3000

3001 to

4000

4001 to

5000

5001 to

6000

6001 to

7000

7001 to

8000

2500 10.0 10.0 10.0 10.0 9.4 8.5 10.0

Orifice Size #55 #55 #55 #55 #55 #55 #56

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/NFPA

54−2002 or National Standard Of Canada, Natural Gas And Propane Installation Code CSA B149.1−05.

NOTE: The derating of these furnaces at 2% (Natural Gas) and 4% (Propane Gas) has been tested and design−certified by

CSA. In Canada, the input rating must be derated 5% (Natural Gas) and 10% (Propane Gas) for altitudes of 2,000 to 4,500

above sea level. Use the 2001 to 3000 column in Table 2, Table 3, Table 4 and Table 5.

The burner orifice part nos. are as follows:

Orifice #41 1096942 Orifice #42 1011351

Orifice #43 1011377 Orifice #44 1011352

Orifice #45 1011353 Orifice #46 1011744

Orifice #47 1011378 Orifice #48 1113201

Orifice #49 1113202 Orifice #54 1011376

Orifice #55 1011354 Orifice #56 1011355

Single Stage Multi Position Furnace

Service Manual

440 08 2011 00

Table 4 NATURAL GAS MANIFOLD PRESSURE ( w.c.) FOR THE90% 80,000 BTUH MODEL AND

ALTERNATE INPUT MODELS

HEATING

VALUE

at ALTITUDE

BTU/CU. FT.

MEAN ELEVATION FEET ABOVE SEA LEVEL

0 to

2000

2001 to

3000

3001 to

4000

4001 to

5000

5001 to

6000

6001 to

7000

7001 to

8000

Orifice

No.

Manifold

Pressure

Orifice

No.

Manifold

Pressure

Orifice

No.

Manifold

Pressure

Orifice

No.

Manifold

Pressure

Orifice

No.

Manifold

Pressure

Orifice

No.

Manifold

Pressure

Orifice

No.

Manifold

Pressure

700 −− −− −− −− −− −− −− −− −− −− −− −− −− −−

725 −− −− −− −− −− −− −− −− −− −− −− −− −− −−

750 −− −− −− −− −− −− −− −− −− −− 41 3.6 41 3.6

775 −− −− −− −− −− −− −− −− 41 3.4 41 3.4 41 3.4

800 −− −− −− −− −− −− 42 3.5 42 3.5 42 3.5 42 3.5

825 −− −− −− −− 42 3.3 42 3.3 42 3.3 42 3.3 42 3.3

850 −− −− −− −− 42 3.1 42 3.1 42 3.1 42 3.1 42 3.1

875 −− −− 43 3.5 43 3.6 43 3.6 43 3.6 43 3.6 43 3.6

900 −− −− 43 3.3 43 3.4 43 3.4 43 3.4 43 3.4 43 3.4

925 44 3.7 44 3.7 44 3.7 44 3.7 44 3.7 44 3.7 44 3.7

950 44 3.5 44 3.5 44 3.5 44 3.5 44 3.5 44 3.5 44 3.5

975 44 3.3 44 3.3 44 3.3 44 3.3 44 3.3 44 3.3 44 3.3

1000 44 3.2 44 3.2 44 3.2 44 3.2 44 3.2 44 3.2 44 3.2

1050 46 3.6 46 3.6 46 3.6 46 3.6 46 3.6 −− −− −− −−

1100 46 3.3 46 3.3 46 3.3 46 3.3 −− −− −− −− −− −−

NOTE: Natural gas data is based on 0.60 specific gravity. For fuels with different specific gravity consult the National Fuel Gas Code ANSI

Z223.1−2002/NFPA 54−2002 or National Standard of Canada, Natural Gas And Propane Installation Code CSA B149.1−05.

Bold indicated the factory shipped orifice size #44.

Table 5 LPG or PROPANE GAS MANIFOLD PRESSURE ( w.c.)

FOR THE 80,000 BTUH MODEL AND ALTERNATE INPUT MODELS

HEATING VALUE

at ALTITUDE

BTU/CU. FT.

MEAN ELEVATION FEET ABOVE SEA LEVEL

0 to

2000

2001 to

3000

3001 to

4000

4001 to

5000

5001 to

6000

6001 to

7000

7001 to

8000

2500 10.0 10.0 9.0 10.0 9.4 8.5 10.0

Orifice Size #54 #54 #54 #55 #55 #55 #56

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/NFPA 54−2002 or National Standard Of Canada, Natural Gas And Propane Installation Code CSA B149.1−05.

NOTE: The derating of these furnaces at 2% (Natural Gas) and 4% (Propane Gas) has been tested and design−certified by

CSA.

In Canada, the input rating must be derated 5% (Natural Gas) and 10% (Propane Gas) for altitudes of 2,000 to 4,500 above

sea level. Use the 2001 to 3000 column in Table 2, Table 3, Table 4 and Table 5.

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% (natu-

ral) or 4% (LP) for each 1000′above sea level in the

USA. In Canada, the input rating must be derated 5%

(natural) or 10% (LP) for each 1000′above sea level.

See Table 4 or Table 5 for required high altitude in-

put rate.

2. For operation with natural gas at altitudes above

2,000′, orifice change and/or manifold pressure ad-

justments may be required for the gas supplied. First

consult your local gas supplier, then refer to Table 2

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 3. Orifices can be ordered through your

distributor. (See Figure 6)

*High Altitude Input Rate =

Nameplate Sea Level Input Rate x (Multiplier)

Elevation

High Altitude

Multiplier

LP Gas*

Standard Input

High Altitude

Multiplier

LP Gas*

80,000 BTUH Input

Model

High Altitude

Multiplier

LP Gas*

Alternate Input

0′- 2000′1.00 1.00 0.80

2001′- 3000′0.90 1.00 0.80

3001′- 4000′0.86 1.00 0.80

4001′- 5000′0.82 1.00 0.80

5001′- 6000′0.78 0.96 0.76

6001′- 7000′0.74 0.92 0.72

7001′- 8000′0.70 0.88 0.68

* Based on mid−range of elevation.

Single Stage Multi Position Furnace Service Manual

440 08 2011 00 11

*High Altitude Input Rate =

Nameplate Sea Level Input Rate x (Multiplier)

Elevation

High Altitude

Multiplier

Natural Gas*

Standard Input

High Altitude

Multiplier

Natural Gas*

80,000 BTUH Input

Model

High Altitude

Multiplier

Natural Gas*

Alternate Input

0′- 2000′1.00 1.00 0.80

2001′- 3000′0.95 1.00 0.80

3001′- 4000′0.93 1.00 0.80

4001′- 5000′0.91 1.00 0.80

5001′- 6000′0.89 1.00 0.80

6001′- 7000′0.87 1.00 0.80

7001′- 8000′0.85 1.00 0.80

* Based on mid−range of elevation.

4. In cases where Table 2 or Table 3 is not applicable,

eg. alternate input rate application, refer to Table 4 or

Table 5 for required high altitude input rate.

Main Burner Flame Check

Allow the furnace to run approximately 10 minutes. Then inspect

the main burner flames. See Figure 5.

Check for the following:

•Stable and blue flames. Dust may cause orange tips

or wisps of yellow, but flames MUST NOT have solid,

yellow tips.

•Flames extending directly from burner into heat ex-

changer.

•Flames do NOT touch sides of heat exchanger

If any problems with main burner flames are noted, it may

be necessary to adjust gas pressures or check for drafts.

Main Burner

Burner Face

10−10−78

Figure 5

Changing Orifices for High Altitude

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.

!WARNING

NOTE: Main burner orifices can be changed for high alti-

tudes.

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 the orifices so they are seated and gas tight

approximately 11/8″from the face of the orifice to the

back of the manifold pipe. (See Figure 6) Make sure

orifice is installed straight so that it forms a right angle

(90°) to the manifold.

5. Reinstall manifold. Ensure burners do NOT bind on

new orifices.

Figure 6 Changing Orifices

11/8″to 13/16″

Measure from face of orifice

to the back side of the

manifold.

NOTE: For Ignitor location see Figure 7.

Ignitor Location

Figure 7

5/16 1/4

21/16

NOTE: Flame sensor has a different orientation for all

050 models and alternate 040 input.

all dimensions are in inches.

High Altitude Installation

Gas input rate on the furnace rating plate is for installation at up to

2000′. The #54 burner orifices supplied in this kit are sized for Pro-

pane Gas at full rate ONLY, for use between 0−2000′elevation. Do

not use them above 2000′(except when noted by Table 3 or

Table 5). Orifices for conversion at high altitude and alternate input

must be ordered from Service Parts.

Standard Input:

Units may be installed at full input rating (25,000 BTUH per heat

exchanger) when installed at altitudes up to 2000′.

80,000 BTUH model and Alternate Input (Conversions): See unit

instructions to determine if model may be converted to alternate in-

put.

Units may be installed at full input rating (20,000 BTUH per heat

exchanger) when installed at altitudes up to 5000′.

Single Stage Multi Position Furnace

Service Manual

440 08 2011 00

In the USA, for furnaces fired on standard rate, the input rating for

altitudes above 2000′(5,000for 80,000 BTUH and alternate in-

put) must be derated by 4% for each 1000′above sea level (see

Table 3 and Table 5)

In Canada, the input rating for altitudes above 2000′(5,000for

80,000 BTUH) must be reduced by 10% for altitudes of 2000′to

4500′above sea level. Use the 2001 to 3000 column in Table 3

and Table 5.

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 6, by

changing the main burner orifices. Changing of burner orifices

MUST be done by a qualified service technician. See section on

changing orifices.

CAUTION: See unit instructions to determine if model may be

converted to alternate input.

Table 6 Alternate Input Ratings, USA ONLY.

BTUH

Standard

Rating

BTUH

Alternate

Rating

Gas

Orifice*

50,000 40,000 #55

75,000 60,000 #55

100,000 80,000 #55

125,000 100,000 #55

* See Table 5 for High Altitude

MANIFOLD PRESSURE AND ORIFICE SIZE FOR HIGH ALTITUDE APPLICATIONS

Table 7 LPG or PROPANE GAS MANIFOLD PRESSURE ( w.c.)

EXCEPT FOR THE 90% 80,000 BTUH MODEL AND ALTERNATE INPUT RATINGS

HEATING VALUE

at ALTITUDE

BTU/CU. FT.

MEAN ELEVATION FEET ABOVE SEA LEVEL

0 to

2000

2001 to

3000

3001 to

4000

4001 to

5000

5001 to

6000

6001 to

7000

7001 to

8000

2500 10.0 10.0 9.0 10.0 9.4 8.5 10.0

Orifice Size #54 #54 #54 #55 #55 #55 #56

Table 8 LPG or PROPANE GAS MANIFOLD PRESSURE ( w.c.)

FOR THE 90% 80,000 BTUH MODEL AND ALTERNATE INPUT RATINGS

HEATING VALUE

at ALTITUDE

BTU/CU. FT.

MEAN ELEVATION FEET ABOVE SEA LEVEL

0 to

2000

2001 to

3000

3001 to

4000

4001 to

5000

5001 to

6000

6001 to

7000

7001 to

8000

2500 10.0 10.0 10.0 10.0 9.4 8.5 10.0

Orifice Size #55 #55 #55 #55 #55 #55 #56

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/NFPA

54−2002 or National Standard Of Canada, Natural Gas And Propane Installation Code CSA B149.1−05.

NOTE: In the USA, for furnaces fired on standard rate, the input rating for altitudes above 2000′(5,000for 80,000 BTUH and alternate

input) must be derated by 4% for each 1000′above sea level (see Table 3 and Table 5)

In Canada, the input rating for altitudes above 2000′(5,000for 80,000 BTUH) must be reduced by 10% for altitudes of 2000′to 4500′

above sea level. Use the 2001 to 3000 column in Table 3 and Table 5.

L.P. PRESSURE SWITCH

Models equipped for or converted to operate on LP Gas will

be equipped with an LP Pressure Switch. If so equipped,

the switch will be located in the gas supply line (in a “Tee”

fitting), just ahead of the gas valve.

The purpose of this switch is to prevent furnace operating

under low line (Supply) pressure conditions. Operating un-

der low line pressure conditions, can create problems such

as incomplete combustion, flashback, sooting, etc.

The switch is a “Normally Open” pressure operated switch

that is wired in series with the furnace (air proving) pressure

switch. The L.P. Pressure Switch closes when line (Supply)

pressure is 8.0″W.C. or higher. the L.P. Pressure Switch

Opens if line pressure falls below 6.0″+0.6″W.C. inter-

rupting power to the gas valve.

Typical L.P. Pressure Switch

Figure 8

Single Stage Multi Position Furnace Service Manual

440 08 2011 00 13

HONEYWELL VR8205S Gas Valve

The VR8205S Gas Valve is a REDUNDANT type valve.

This means that it consists of two (2) valves (internally) with

independent operators (solenoids) that both must be ener-

gized before gas can flow through the valve. This redundan-

cy provides an added safety measure. In case one of the

valves sticks open (Mechanically), the second operator will

close preventing the flow of gas.

If the valve does not open, check for 24 Volts across the two

wires to the valve during a call for heat. This check MUST

be made IMMEDIATELY following the igniter warm−up peri-

od (17 seconds). 24 Volts will be present ONLY for a period

of 7 seconds after the igniter warm−up if flame is not proven.

If 24 Volts is present during the above check and the valve

will NOT open, then replace the valve. If 24 Volts IS NOT

present, problems are indicated in the control and/or wiring

to the gas valve.

HIGH ALTITUDE OPERATION

These furnaces are designed to operate in the majority of

the country without modifications. At altitudes over 2,000′

above sea level, however, certain measures need to be tak-

en to insure continued, safe reliable operation. For exam-

ple, units must be de−rated for altitude (by adjusting man-

ifold pressure and/or changing orifice size) based upon the

type of fuel (I.E. Natural Gas or L.P. gas), Btu content of the

gas, and installed altitude.

Altitudes over 4,000′may require a different air proving

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 or switch. Check with governing au-

thorities.

When servicing a unit installed at altitudes above 2,000′in-

sure that it has been properly modified to operate at that alti-

tude. See the sections on Gas pressure (Page 10), and

pressure switches (Page 15) to obtain specific information

for you particular installation altitude.

CHECKING TEMPERATURE RISE

Air Flow

Checking Temperature Rise

Figure 9

Thermometer:

Return Air Temp.

Thermometer;

Supply Air Temp.

Supply

Air Flow

Return

Temperature Rise Check

The blower speed MUST be set to give the correct air tem-

perature rise through the furnace as marked on the rating

plate. Temperature rise is the difference between supply

and return air temperatures.

To check temperature rise,use the following procedure:

1. Place thermometers in supply and return air registers

as close to furnace as possible, avoiding direct ra-

diant heat from heat exchangers.

2. Operate furnace continuously for 15 minutes with all

registers and duct dampers open.

3. Take reading and compare with range specified on

rating plate.

4. If the correct amount of temperature rise is NOT ob-

tained, it may be necessary to change blower speed.

A higher blower speed will lower the temperature rise.

A lower blower speed will increase the temperature

rise.

NOTE: BEFORE CHECKING TEMPERATURE RISE BE

CERTAIN THAT MANIFOLD PRESSURE IS PROPERLY

ADJUSTED.

ALLOWABLE TEMPERATURE RISE ALL MODELS

Model Range

50, 80 Mbtu 35°F −65°F

75, 100 & 125 Mbtu 40°F −70°F

Example:

Supply Temp. 170°

Return Temp. 70°

Temperature Rise 100°= Too High

Solution: Increase Blower Speed

Single Stage Multi Position Furnace

Service Manual

440 08 2011 00

ROOM THERMOSTATS

Room thermostats are available from several different

manufactures in a wide variety of styles. They range from

the very simple and inexpensive Bi−metallic type to the

complex and costly electronic set−back type. They are sim-

ply a switch (or series of switches) designed to turn equip-

ment (or components) “ON” or “OFF” at the desired condi-

tions.

An improperly operating, or poorly located room thermostat

can be the source of perceived equipment problems. A

careful check of the thermostat and wiring must be made

then to insure that it is not the source of problems.

Thermostat Location

Figure 10

5 ft.

DRAFTS

SUN

THERMOSTAT

LIGHT

SHIELD

LOCATION

The thermostat should not be mounted where it may be af-

fected by drafts, discharge air from registers (hot or cold),

or heat radiated from the sun or appliances. Never install in

alcoves, bathrooms or bedrooms.

The thermostat should be located about 5 ft. above the floor

in an area of average temperature, with good air circulation.

Normally, an area in close proximity to the return air grille

is the best choice.

Mercury bulb type thermostats MUST be level to control

temperature accurately to the desired set−point. Electronic

digital type thermostats SHOULD be level for aesthetics.

HEAT ANTICIPATORS

Heat anticipators are small resistance heaters built into

most electric−mechanical thermostats. Their purpose is to

prevent wide swings in room temperature during furnace

operation.

In order to accomplish this, the heat output from the antici-

pator must be the same regardless of the current flowing

through it. Consequently, most thermostats have an adjust-

ment to compensate for varying current draw in the thermo-

stat circuit.

The proper setting of heat anticipators then is important to

insure proper temperature control and customer satisfac-

tion.

Measuring Current Draw

Figure 11

Ammeter

Subbase

Amps

The best method to obtain the required setting for the heat

anticipator, is to measure the actual current draw in the con-

trol circuit (“W”) using a low range (0−2.0 Amps) Ammeter.

(See Figure 11) After measuring the current draw, simply

set the heat anticipator to match that value.

If a low range ammeter is not available, a “Clamp−on” type

meter may be used as follows:

1. Wrap EXACTLY ten (10) turns of wire around the jaws

of a clamp−on type ammeter.

2. Connect one end of the wire to the “W” terminal of the

thermostat sub−base, and the other to the “R” termi-

nal.

3. Turn power on, and wait approximately 1 minute, then

read meter.

4. Divide meter reading by 10 to obtain correct anticipa-

tor setting.

Electronic thermostats do not use a resistance type antici-

pator. These thermostats use a microprocessor (computer)

that determines a cycle rate based on a program loaded into

it at the factory.

These cycle rates are normally field adjustable for different

types to equipment. The method of adjustment, however,

varies from one thermostat manufacturer to another. Check

with the thermostat manufacturer to find out the proper way

of adjusting the cycle rate.

CONTROL WIRING

Control wiring is an important part of the total equipment

installation, since it provides the vital communications link

between the thermostat, and the equipment. Control wiring

that is either too long, undersized, or improperly connected

(be it simply loose, or on the wrong terminal) can in fact be

the source of many equipment problems.

Single Stage Multi Position Furnace Service Manual

440 08 2011 00 15

ALWAYS check to make sure that the control wiring is con-

nected to the proper terminal(s) of the equipment and ther-

mostat you are using. Remember, also, that the thermostat

terminals are not always identified alike by different thermo-

stat manufacturers. Connections MUST be clean and tight

to insure trouble−free operation.

ELECTRONIC CONTROLS used on this series of furnace

RESPOND DIFFERENTLY to certain control wiring practic-

es which have been generally accepted in the HVAC indus-

try for many years.

For Example: For years, installers have run a wire from the

“Y” terminal of the room thermostat and connected it direct-

ly to the contact on coil of a condensing unit. (not making

any connection to the furnace with this wiring. Then, run the

low voltage “Common” wire from the condensing unit back

to the “C” terminal of the furnace.

With the electronic Furnace Control Board used in this se-

ries, however the “Y” terminal of the furnace does in fact

serve a particular purpose. Failure to connect it will result

in certain improper operation as follows:

The COOLING fan speed is energized via the “Y” terminal.

Failure to connect the thermostat “Y” terminal to the “Y”

terminal on the control will result in the failure to energize

the COOLING speed on a call for cooling from the thermo-

stat. (The HEATING speed will be energized instead via the

“G” terminal)

TWINNING KITS

Some installations may require a Heating capacity or Air-

flow capabilities greater than a single furnace of this series

can provide. When this is necessary, furnaces may be

installed in a “Twinned” configuration.

The Twinning Kit allows the two (2) identical furnaces to be

controlled by the same room thermostat. When Twinned,

the circulating (conditioned air) blowers of BOTH furnaces

will operate simultaneously. The kit part no. for the “C” se-

ries or later furnace is NAHA004WK.

LIMIT SWITCHES

Two (2) different kinds of limit switches are used on this se-

ries of furnaces. They are the main limit and roll out limit

switch. The main limit, and roll limit switches are used on

ALL models.

NOTE: All limit switches are safety devices and other

than for testing purposes, should never be jumped out!

Limit switches are “normally closed” electrical switches, de-

signed to open when their predetermined “limit setting” has

been reached.

It should also be remembered, that when a limit switch

opens, it more than likely is not due to a bad switch! The

cause of the opening limit must be found and corrected, be-

fore the furnace can resume proper operation.

FIRE HAZARD.

Failure to do so can result in death, personal injury

and/or property damage.

Limit controls are factory preset and MUST NOT be

adjusted. Use ONLY manufacturer’s authorized

replacement parts.

The specific functions of the two (2) limit switches

used in this series of furnaces are as follows:

MAIN LIMIT SWITCH

There is a “Normally Closed” switch located on the front

partition of the furnace. It monitors supply air temperature,

and interrupts furnace (burner) operation when a supply air

temperature is sensed which would result in the furnace ex-

ceeding Maximum allowable outlet air temperature. While

the main limit is open, the combustion blower, and the circu-

lating blower will be energized continuously. This control is

an “Automatic” reset control, which will reset itself when the

temperature sensed drops to a safe level.

If furnace (burner) cycles on this limit switch, (I.E. switch

opens and closes during furnace operation) it is more than

likely due to a high temperature rise through the furnace.

(See checking temperature on page 10 of this manual)

High temperature rise can be caused by either OVER

FIRING (high manifold pressure. incorrect orifices, etc.) or

LOW AIR FLOW (dirty filter, blower speed too low, exces-

sive static in duct system, etc.)

Single Stage Multi Position Furnace

Service Manual

440 08 2011 00

N9MP1 & N9MP2 MAIN LIMIT SWITCH

MODEL PART # OPEN CLOSE

050B12C 34335002 240°F 220°F

075B12C 34335001 210°F 190°F

080F16C 1320361 230°F 210°F

100F14C 1320361 230°F 210°F

100J20C 1320367 220°F 200°F

125J20C 1008445 190°F 170°F

ROLL OUT LIMIT SWITCH

MODEL PART # OPEN CLOSE

ALL 1013102 300°F MANUAL

*9MPD MAIN LIMIT SWITCH

MODEL PART # OPEN CLOSE

050B12C 1320366 260°F 240°F

075F12C 34335002 240°F 220°F

080J16C 1320367 220°F 200°F

100J14C 1320367 220°F 200°F

100J20C 1320367 220°F 200°F

125L20C 1008445 190°F 170°F

ROLL OUT LIMIT SWITCH

MODEL PART # OPEN CLOSE

ALL 1013102 300°F MANUAL

To verify this, the cut−out (opening) point of the switch

should be checked (using a thermocouple type thermome-

ter connected to the face of the switch) as follows:

1. Operate furnace for several minutes.

2. Block return air grille(s) to furnace.

3. Observe temperature at which switch opens (burner

operation ceases).

4. Remove blockage from return grille(s).

5. Observe temperature at which switch closes (burner

operation resumes).

6. Compare readings with the limit setting listed in the

appropriate chart for the model you are servicing.

If switch is opening within the specified range, then it is sim-

ply doing its job, and the cause of the over−temperature

must be determined and corrected.

If, however, the switch is found to be opening prematurely,

then it should be replaced. When replacing ANY limit

switch, use ONLY a switch of EXACTLY the same tempera-

ture setting. Use of a different temperature limit switch can

create a dangerous situation. Some of the main limit

switches used in this series are SIMILAR IN AP-

PEARANCE. DIFFERENT TEMPERATURE SETTINGS,

HOWEVER, ARE USED for different models. Be certain

you have the correct control for the model you are servicing.

ROLL OUT LIMIT

A “Normally Closed” switch (wired in series with the Main

Limit switch) mounted on both sides of the burner box.

This switch is a manual reset type. When replacing this

switch, be absolutely certain the correct one is used.

Typical Roll Out Limit Switch

Figure 12

NEVER use an automatic reset roll out switch to

replace a manual reset type roll out switch.

Doing so may cause potentially unsafe and/or

intermittent operation.

!CAUTION

The roll out switch monitors the temperature inside the

burner box, and interrupts furnace (burner) operation when

its temperature indicates flame roll out has occurred.

Once the roll out switch has opened, burner operation will

be prevented until the roll out switch is “Manually Reset” by

pressing the red button located on the switch. While the roll

out switch is open, the combustion blower and circulating

blower will be energized continuously.

If the roll out switch has opened, the cause must be deter-

mined. Some possible reasons for flame roll out include a

restricted primary or secondary heat exchanger or over

fired furnace.

PRESSURE SWITCHES

Transition Pressure Switch

An air proving switch (pressure) switch is used on all mod-

els to insure that a draft has been established through the

heat exchanger before allowing burner operation.

All models use a single tap (port) type switch. This switch

senses the negative pressure created by (at) the combus-

tion blower.

Under normal operating conditions, sufficient pressure is

developed by the exhaust (combustion) blower to close the

Single Stage Multi Position Furnace Service Manual

440 08 2011 00 17

switch, and permit the burner to operate. As the condensate

drain begins to back−up, however, the pressure begins to

reduce. When the pressure drops sufficiently, burner opera-

tion will be prevented until the condition is corrected.

N9MP1 STANDARD TRANSITION SWITCH

MODEL PART # OPEN ″W.C. CLOSE″W.C

050B12C 1013802 −2−2.2

075B12C 1013802 −2−2.2

080F16C 1013811 −1.6 −1.8

100F14C 1013801 −2.1 −2.3

100J20C 1013802 −2−2.2

125J20C 1013166 −1.6 −1.8

N9MP1 STANDARD INDUCER SWITCH

MODEL PART # OPEN ″W.C. CLOSE ″W.C.

125J20C 1013166 −1.1 −1.3

N9MP1 HIGH ALTITUDE TRANSITION SWITCH

MODEL PART # OPEN ″W.C. CLOSE ″W.C.

050B12C 1013803 −1.8 −2

075F12C 1013803 −1.8 −2

080F16C 1013812 −1.3 −1.5

100F14C 1013803 −1.8 −2

100J20C 1013803 −1.8 −2

125L20C 1013157 −1.5 −1.7

N9MP1 HIGH ALTITUDE INDUCER SWITCH

MODEL PART # OPEN ″W.C. CLOSE ″W.C.

125J20C 1013157 −0.7 −0.9

Pressure Switch

Figure 13

Pressure Port

Normally Open

Terminal

Common

Terminal

N9MP2 STANDARD TRANSITION SWITCH

MODEL PART # OPEN ″W.C. CLOSE″W.C

050B12C 1013802 −2−2.2

075B12C 1013801 −2.1 −2.3

080F16C 1013811 −1.6 −1.8

100F14C 1013801 −2.1 −2.3

100J20C 1013802 −2−2.2

125J20C 1013166 −1.6 −1.8

N9MP2 STANDARD INDUCER SWITCH

MODEL PART # OPEN ″W.C. CLOSE ″W.C.

125J20C 1013166 −1.1 −1.3

N9MP2 HIGH ALTITUDE TRANSITION SWITCH

MODEL PART # OPEN ″W.C. CLOSE ″W.C.

050B12C 1013803 −1.8 −2

075F12C 1013803 −1.8 −2

080F16C 1013812 −1.3 −1.5

100F14C 1013803 −1.8 −2

100J20C 1013803 −1.8 −2

125L20C 1013157 −1.5 −1.7

N9MP2 HIGH ALTITUDE INDUCER SWITCH

MODEL PART # OPEN ″W.C. CLOSE ″W.C.

125J20C 1013157 −0.7 −0.9

*9MPD STANDARD TRANSITION SWITCH

MODEL PART # OPEN ″W.C. CLOSE″W.C

050B12C 1013802 −2−2.2

075B12C 1013802 −2−2.2

080F16C 1013812 −1.3 −1.5

100F14C 1013802 −2−2.2

100J20C 1013802 −2−2.2

125J20C 1013166 −1.6 −1.8

*9MPD STANDARD INDUCER SWITCH

MODEL PART # OPEN ″W.C. CLOSE ″W.C.

125J20C 1013166 −1.1 −1.3

*9MPD HIGH ALTITUDE TRANSITION SWITCH

MODEL PART # OPEN ″W.C. CLOSE ″W.C.

050B12C 1013803 −1.8 −2

075B12C 1013803 −1.8 −2

080F16C 1013813 −1−1.2

100F14C 1013803 −1.8 −2

100J20C 1013803 −1.8 −2

125L20C 1013157 −1.5 −1.7

*9MPD HIGH ALTITUDE INDUCER SWITCH

MODEL PART # OPEN ″W.C. CLOSE ″W.C.

125J20C 1013157 −0.7 −0.9

To insure continued SAFE, RELIABLE, operation NEVER

SUBSTITUTE a pressure switch with one that is similar in

Single Stage Multi Position Furnace

Service Manual

440 08 2011 00

appearance. ONLY FACTORY PROVIDED or AU-

THORIZED SUBSTITUTES ARE ACCEPTABLE.

Furnaces installed at altitudes of 4,000′above sea level or

higher may require replacing the standard pressure switch

with a high altitude pressure switch. The different pressure

switch settings allow continued SAFE RELIABLE high alti-

tude operation.

Under normal operating conditions, sufficient negative

pressure will be created to close the pressure switch, and

keep it closed to keep furnace operating. Under abnormal

conditions, however, such as a restricted vent pipe, or a

leak in one of the heat exchangers, sufficient negative pres-

sure will not be created. This will result in the switch failing

to close or failing to remain closed during furnace operation.

When servicing a unit whose pressure switch will not close,

or remain closed during operation, the operating pressure

of that furnace should be checked and compared to

approximate operating pressures listed in this manual and

the switch setting(s) listed above for the model family you

are servicing.

It is important to remember, that greater negative pressures

are created by the furnace when “HOT” (I.E. upon initial

start−up) than when “COLD” (I.E. after furnaces has been

in operation for a few minutes). Because of this, furnace

pressure should ONLY be checked when “HOT” to insure

accurate readings.

The tables list approximate operating pressures. They are

included in this manual to provide you with a “Barometer”

to gauge your pressures against. The pressures you obtain

in the field will differ slightly from these figures based upon

vent length, gas pressure, operating temperature, etc.

Major discrepancies in pressures, will normally cause

problems with pressure switch operation. These Major dis-

crepancies should be investigated as follows:

Lower (Lesser) Negative Pressures

Lower than normal negative pressures measured at the

Combustion Blower may be caused by:

1. Restriction on the Outlet side of the combustion blow-

er. (I.E. Blocked Flue, Vent too long, Heat Exchanger

leak, etc.)

2. Leak (lack of restriction) on the Inlet side of the com-

bustion blower.

Higher (Greater) Negative Pressures

Higher than normal negative pressures measured at the

Combustion Blower may be caused by:

1. Restriction on the Inlet side of the combustion blower.

(I.E. Plugged Heat Exchanger, air inlet orifice too

small)

Vent Pipes MUST be

supported Horizontally

and Vertically

*8″Min.

20′Max.

in same atmospheric

zone

*8″Min.

20′Max.

in same

atmospheric

zone

Coupling on ends of

exhaust pipe. Total

pipe & coupling out-

side structure = 8″

Figure 14 Typical Upflow Installation

Aluminum or non−rusting shield recommended. (See

Vent Termination Shielding for dimensions).

*Increase minimum from 8″to 18″for cold climates (sustained temperatures below

0 °F).

DISCHARGE AIR

25−23−33

Inlet Pipe (not

used on Single

Pipe model)

*8″Min.

20′Max.

in same

atmospheric zone

Figure 15 Typical Downflow Installation

Vent Pipes MUST be

supported Horizontally

and Vertically

* Increase minimum from 8″to 18″for cold climates (sustained temperatures

below 0°F).

See Vent Termination

Shielding in Vent Sec-

tion.

*8″Min.

20′Max.

in same

atmospheric zone

8″Min.

Coupling on inside

and outside of wall

to restrain vent pipe

25−23−33a

Inlet Pipe

(not used on

Single Pipe

model)

Single Stage Multi Position Furnace Service Manual

440 08 2011 00 19

VENT/COMBUSTION AIR PIPING

Vent and combustion air piping are an extremely important

part of the total furnace installation. Improperly installed or

inadequately sized vent and/or combustion air piping can

be the source of many perceived furnace problems.

For example, most problems associated with pressure

switch operation can normally be traced to short comings

in the vent and/or combustion air piping. Anytime these type

problems arise, a thorough inspection of the vent and/or

combustion air piping should be conducted.

ALL MODELS require a vent (exhaust) pipe to carry flue

products to the outside of the structure.

Direct VENT (ONLY) models require a combustion air inlet

to bring in all air for combustion from outside the struc-

ture.

DUAL CERTIFIED models require a combustion air inlet

pipe to bring in all air for combustion from outside the struc-

ture only when installed as a Direct Vent Furnace (I.E. Two

Pipe Installation)

Consult the appropriate Venting tables and/or piping chart

for the model you are servicing.

STANDARD VENT TERMINATION

Vent/Combustion Air Piping Charts

Sizing Combustion Air and Vent Pipe

Consult Table 9 or Table 10 to select the proper diameter

exhaust and combustion air piping. Exhaust and combus-

tion air piping is sized for each furnace Btuh size based on

total lineal vent length (on inlet or outlet side), and number

of 90°elbows required. Two 45°elbows can be substituted

for one 90°elbow. The elbow or elbows used for vent ter-

mination outside the structure ARE counted, including el-

bows needed to bring termination above expected snow

levels. The elbow inside the furnace on the *9MPD IS NOT

included in the count.

Table 9 Pipe Diameter Table

N9MP1 & *9MPD Models

50,000, 75,000 & 80,000 Btuh Furnaces

40′& (5) 90°elbows with 2″PVC pipe or

70′& (5) 90°elbows with 3″PVC pipe

100,000 Btuh Furnace

40′& (5) 90°elbows with 3″PVC pipe or

70′& (5) 90°elbows with 3″PVC pipe &

Long Vent Kit (See Tech. Manual)

125,000 Btuh Furnace

40′& (5) 90°elbows with 3″PVC pipe

Elbows are DWV Long Radius Type for 2″and 3″vents.

If more than five elbows are required, reduce the length of

both the inlet and exhaust pipes 5′for each additional elbow

used.

NOTE: It is allowable to use larger diameter pipe and fitting than

shown in the tables but not smaller diameters than shown.

Table 10 Pipe Diameter Table

N9MP2 Models

50,000 & 80,000 Btuh Furnaces

40′& (5) 90°elbows with 2″PVC pipe or

70′& (5) 90°elbows with 3″PVC pipe

75,000 Btuh Furnaces

25′& (3) 90°elbows with 2″PVC pipe or

40′& (5) 90°elbows with 2″PVC pipe &

Long Vent Kit (See Tech. Manual) or

70′& (5) 90°elbows with 3″PVC pipe

100,000 Btuh Furnace

40′& (5) 90°elbows with 3″PVC pipe or

70′& (5) 90°elbows with 3″PVC pipe &

Long Vent Kit (See Tech. Manual)

125,000 Btuh Furnace

40′& (5) 90°elbows with 3″PVC pipe

Elbows are DWV Long Radius Type for 2″and 3″vents.

If more than five elbows are required, reduce the length of

both the inlet and exhaust pipes 5′for each additional elbow

used.

NOTE: It is allowable to use larger diameter pipe and fitting than

shown in the tables but not smaller diameters than shown.

AIR SUPPLY INLET

VVENT TERMINAL AREA WHERE TERMINAL IS NOT PERMITED

25−24−65−2

Direct Vent Termination Clearance

Figure 16

Single Stage Multi Position Furnace

Service Manual

440 08 2011 00

Item Clearance Description Canadian Installation (1) U.S. Installation (2)

AClearance above grade, veranda, porch, deck, balcony, or

anticipated snow level

12″(30cm) # 12″(30 cm)

BClearance to a window or door that may be opened 6″(15 cm) for appliances ≤10,000 BTUH (3kW), 12″(30

cm) for appliances > 10,000 Btuh (3 kW) and ≤100,000 Btuh

(30 kW), 36″(91 cm) for appliances > 100,000 Btuh (30 kW)

6″(15 cm) for appliances ≤10,000 BTUH (3kW), 9″(23 cm)

for appliances > 10,000 Btuh (3 kW) and ≤50,000 Btuh (15

kW), 12″(30 cm) for appliances > 50,000 Btuh (15 kW)

CClearance to a permanently closed window * *

DVertical clearance to a ventilated soffit located above the

terminal within a horizontal distance of 2′(61cm) from the

centerline of the terminal

* *

EClearance to an unventilated soffit * *

FClearance to an outside corner * *

GClearance to an inside corner * *

HClearance to each side of the centerline extended above

electrical meter or gas service regulator assembly

3′(91 cm) within 15′(4.5 m) above the meter/regulator

assembly

3′(91 cm) within 15′(4.5 m) above the meter/regulator

assembly

IClearance to service regulator vent outlet 3′(91 cm) *

JClearance to non−mechanical air supply inlet to building or the

combustion air inlet to any other appliance

6″(15 cm) for appliances ≤10,000 BTUH (3kW), 9″(23 cm)

for appliances > 10,000 Btuh (3 kW) and ≤100,000 Btuh (30

kW) and ≤50,000 Btuh (15 kW), 12″(30 cm) for appliances

> 50,000 Btuh (15 kW)

6″(15 cm) for appliances ≤10,000 BTUH (3kW), 9″(23 cm)

for appliances > 10,000 Btuh (3 kW) and ≤50,000 Btuh (15

kW), 12″(30 cm) for appliances > 50,000 Btuh (15 kW)

KClearance to a mechanical air supply inlet 6′(1.83 m) 3′(91 cm) above if within 10′(3m) horizontally

LClearance under a veranda, porch, deck, or balcony 12″(30 cm) + *

MClearance to each side of the centerline extended above or

below vent terminal of the furnace to a dryer or water heater

vent, or other appliance’s direct vent intake or exhaust.

12″(30 cm) 12″(30 cm)

NClearance from a plumbing vent stack 3′(91 cm) 3′(91 cm)

OClearance above a paved sidewalk or paved driveway located

on public property.

7′(2.13 m) 7′(2.13 m)

(1. ) In accordance with the current CSA B149.1, Natural Gas and Propane Installation Code

(2. ) In accordance with the current ANSI Z223.1/NFPA 54, National Fuel Gas Code

# 18″(46 cm) above roof surface

+ Permitted only if veranda, porch, deck, or balcony is fully open on a minimum of two sides beneath the floor.

*For clearances not specified in ANSI Z223.1/NFPA 54 or CSA B149.1, clearances shall be in accordance with local installation codes and the requirements of the gas supplier and the

manufacture’s installation instructions.

** A vent shall not terminate directly above a sidewalk or paved driveway that is located between two single family dwellings and serves both dwellings.

Notes:

1. The vent for this appliance shall not terminate

a. Over public walkways; or

b. Near soffit vents or crawl space vents or other areas where condensate or vapor could create a nuisance or hazard or property damage; or

c. Where condensate vapor could cause damage or could be detrimental to the operation of regulators, relief valves, or other equipment.

2. When locating vent terminations, consideration must be given to prevailing winds, location, and other conditions which may cause recirculation of the combustion products of adjacent vents.