ICP F9MXT1002120A, F9MXT0601714A, F9MXT0801716A, F9MXT0802120A, F9MXT1202422A Service And Technical Support Manual

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Page 1

Printed in U.S.A. 440 04 4321 04 July 2012

SERVICE AND TECHNICAL

SUPPORT MANUAL

Two−Stage, ECM Blower Motor

35” Tall, High Efficiency Condensing Gas Furnace

(F/G)9MXT

Save this manual for future reference.

Safety Labeling and Signal Words

DANGER, WARNING, CAUTION, and NOTE

The signal words DANGER, WARNING, CAUTION, and NOTE are used to identify levels of

hazard seriousness. The signal word DANGER is only used on product labels to signify an immediate hazard. The signal words WARNING, CAUTION, and NOTE will be used on product labels and throughout this manual and other manual that may apply to the product.

DANGER − Immediate hazards which will result in severe personal injury or death.

WARNING − Hazards or unsafe practices which could result in severe personal injury or death.

CAUTION − Hazards or unsafe practices which may result in minor personal injury or product or property damage.

NOTE − Used to highlight suggestions which will result in enhanced installation, reliability, or operation.

WARNING

Signal Words in Manuals

The signal word CAUTION is used throughout this manual in the following manner:

CAUTION

Signal Words on Product Labeling

Signal words are used in combination with colors and/or pictures or product labels.

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 personal injury.

TABLE OF CONTENTS

START−UP, ADJUSTMENT, AND SAFETY CHECK 4...........

THERMOSTAT SETUP SWITCH 4...........................

PRIME CONDENSATE TRAP WITH WATER 4.................

PURGE GAS LINES 4......................................

ADJUSTMENTS 5.........................................

ADJUST TEMPERATURE RISE 10............................

ADJUST BLOWER OFF DELAY (HEAT MODE) 11..............

ADJUST COOLING AIRFLOW 11.............................

ADJUST CONTINUOUS FAN AIRFLOW 11....................

ADJUST THERMOSTAT HEAT ANTICIPATOR 11...............

CHECK SAFETY CONTROLS 12.............................

CHECKLIST 12.............................................

SERVICE AND MAINTENANCE PROCEDURES 13.............

ELECTRICAL CONTROLS AND WIRING 13...................

TROUBLESHOOTING 13....................................

CLEANING AND/OR REPLACING AIR FILTER 15..............

BLOWER MOTOR AND WHEEL MAINTENANCE 15............

CLEANING BURNERS AND FLAME SENSOR 17...............

SERVICING HOT SURFACE IGNITER 18......................

FLUSHING COLLECTOR BOX AND DRAINAGE SYSTEM 18....

CLEANING CONDENSATE DRAIN AND TRAP 19..............

CLEANING HEAT EXCHANGERS 19..........................

SERVICE LABEL 21.........................................

WIRING DIAGRAM 22.......................................

SEQUENCE OF OPERATION 25.............................

PARTS REPLACEMENT INFORMATION GUIDE 29.............

PRODUCT NOMENCLATURE 30.............................

MODELS

(F/G)9MXT0401410A (F/G)9MXT0601714A (F/G)9MXT0801716A (F/G)9MXT0802120A (F/G)9MXT1002120A (F/G)9MXT1202422A

Use of the AHRI Certified TM Mark indicates a manufacturer’s participation in the program. For verification of certification for individual products, go to www.ahridirectory.org .

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440 04 4321 04

Specifications are subject to change without notice.

SAFETY CONSIDERATIONS

Improper installation, adjustment, alteration, service, maintenance, or use can cause explosion, fire, electrical shock, or other conditions which may cause death, personal injury, or property damage. Consult a qualified installer, service agency, or your distributor or branch for information or assistance. The qualified installer or agency must use factory−authorized kits or accessories when modifying this product. Refer to the individual instructions packaged with the kits or accessories when installing.

Follow all safety codes. Wear safety glasses, protective clothing, and work gloves. Use quenching cloth for brazing operations. Have fire extinguisher available. Read these instructions thoroughly and follow all warnings or cautions included in literature and attached to the unit. Consult local building codes, the current editions of the National Fuel Gas Code (NFCG) NFPA 54/ANSI Z223.1, and the National Electrical Code (NEC) NFPA 70.

In Canada refer to the current editions of the National standards of Canada CAN/CSA−B149.1 and .2 Natural Gas and Propane Installation Codes, and Canadian Electrical Code CSA C22.1.

Recognize safety information. This is the safety−alert symbol

. When you see this symbol on the unit and in instructions or manuals, be alert to the potential for personal injury. Understand these signal words; DANGER, WARNING, and CAUTION. These words are used with the safety−alert symbol. DANGER identifies the most serious hazards which will result in severe personal injury or death. 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 is used to highlight suggestions which will result in enhanced installation, reliability, or operation.

WARNING

PERSONAL INJURY, AND/OR PROPERTY DAMAGE HAZARD

Failure to carefully read and follow this warning could result in equipment malfunction, property damage, personal injury and/or death. Installation or repairs made by unqualified persons could result in equipment malfunction, property damage, personal injury and/or death. The information contained in this manual is intended for use by a qualified service technician familiar with safety procedures and equipped with proper tools and test instruments. Installation must conform with local building codes and with the Natural Fuel Gas Code (NFCG) NFPA 54/ANSI Z223.1, and National standards of Canada CAN/CSA−B149.1 and .2 Natural Gas and Propane Installation Codes.

WARNING

ELECTRICAL SHOCK HAZARD

Failure to follow this warning could cause personal injury or death.

Before performing service or maintenance operations on unit, always turn off main power switch to unit and install lockout tag. Unit may have more than one power switch.

WARNING

CARBON MONOXIDE POISONING AND FIRE HAZARD

Failure to follow safety warnings could result in personal injury, death, and/or property damage.

This furnace is not designed for use in mobile homes, trailers or recreational vehicles.

CAUTION

CUT HAZARD

Failure to follow this caution may result in damage personal injury.

Sheet metal parts may have sharp edges or burrs. Use care and wear appropriate protective clothing, safety glasses and gloves when handling parts and servicing furnaces.

Page 3

SERVICE AND TECHNICAL MANUAL Gas Furnace: (F/G)9MXT

440 04 4321 04 3

Specifications subject to change without notice.

START−UP CHECK SHEET

For PSC Models (F/G)9MXT

(This sheet is optional. Keep for future reference.)

Date of Start−Up:

Dealer Name:

Address:

City, State(Province), Zip or Postal Code:

Phone:

Owner Name:

Address:

City, State(Province), Zip or Postal Code:

Model Number:

Serial Number:

Setup Checks

Check the box when task is complete.

All Electrical Connections Tight?

Have hoses been relocated for furnace U/D/H application?

Condensate Drain Connected?

Condensate Drain Trapped?

Manual Gas Shut−off Upstream of Furnace/Drip Leg

Gas Valve turned ON?

Type of Gas: Natural: Propane:

Filter Type and Size:

Shade in Heating Fan “Time OFF” Setting and Thermostat Type setting:

OFF

1 2 3

TT OFF DLY

Calculated Input (BTU) Rate: (See Checks and Adjustments

Section).

Heating Check

Measured Line Pressure During High Heat:

Measured Manifold Pressure: High Heat

Low Heat

Temperature of Supply Air: High Heat

Low Heat

Temperature of Return Air:

Temperature Rise (Supply − Return): High Heat

Low Heat

In Rise Range (see furnace rating plate)?

Static Pressure (Ducts) High Heat: Supply

Return

The Blower Speed Tap used for: High Heat

Low Heat

Optional Check: CO?

CO2?

Cooling Check

Temperature of Supply Air:

Temperature of Return Air:

Temperature Difference:

Static Pressure (Ducts) Cooling: Supply

Return

The Blower Speed Tap used for: Cooling

Dealer Comments:

Page 4

SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: (F/G)9MXT

START−UP, ADJUSTMENT, AND SAFETY CHECK

General

1. Furnace must have a 115-v power supply properly connected and grounded.

NOTE: Proper polarity must be maintained for 115-v wiring. Control status indicator light flashes code 10 and furnace does not operate if polarity is incorrect or if the furnace is not grounded.

Thermostat wire connections at terminals R, W/W1, G,

2. and Y/Y2 must be made at 24-v terminal block on furnace control.

3. Natural gas service pressure must not exceed 0.5 psig (14-in. w.c., 350 Pa), but must be no less than 0.16 psig (4.5-in. w.c., 1125 Pa).

4. Blower door must be in place to complete 115-v electrical circuit and supply power to the furnace components.

CAUTION

UNIT OPERATION HAZARD

Failure to follow this caution may result in intermittent unit operation or performance dissatisfaction.

These furnaces are equipped with a manual reset limit switch in burner assembly. This switch opens and shuts off power to the gas valve if an overheat condition (flame rollout) occurs in the burner assembly/enclosure. Correct inadequate combustion-air supply, improper gas pressure setting, improper burner or gas orifice positioning, or improper venting condition before resetting switch. DO NOT jumper this switch.

Before operating furnace, check flame rollout manual reset switch for continuity. If necessary, press button to reset switch.

EAC-1 terminal is energized whenever blower operates. HUM terminal is only energized when the the gas valve is energized in heating.

Thermostat Setup Switch

This furnace can be installed with either a single−stage heating or a two−stage heating thermostat. Setup switch SW−1 (TT) is used to configure the furnace for single or two stage thermostat operation. (See Figure 4)

For single−stage thermostats, connect thermostat W to W/W1 at furnace control terminal block. (See Figure 7) For single−stage thermostats, the control will operate for 12 minutes on low heat, then switch to high heat if heat call remains. Setup switch SW−1 (TT) must be in the factory−shipped OFF position. See Figure 7 and Figure 15 for setup switch information.

If a two−stage heating thermostat is to be used, move setup switch SW−1 (TT) to ON position before starting furnace. This overrides built−in control process for selecting high and low heat and allows the two−stage thermostat to select gas heating modes. The W2 from thermostat must be connected to W2 on control terminal block.

Prime Condensate Trap with Water

! WARNING

FIRE OR EXPLOSION HAZARD

Failure to follow these warnings could result in personal injury or death.

Failure to use a properly configured trap or NOT water-priming trap before operating furnace may allow positive pressure vent gases to enter the structure through drain tube. Vent gases contain carbon monoxide which is tasteless and odorless.

1. Remove upper and middle collector box drain plugs opposite of the condensate trap. (See Figure 1)

2. Connect field-supplied 5/8-in. (16 mm) ID tube with attached funnel (see Figure 1) to upper collector box drain connection.

3. Pour one quart (liter) of water into funnel/tube. Water should run through collector box, overfill condensate trap, and flow into open field drain.

4. Remove funnel; replace collector box drain plug.

5. Connect field-supplied 5/8-in. (16 mm) ID tube to middle collector box drain port.

6. Pour one quart (liter) of water into funnel/tube. Water should run through collector box, overfill condensate trap, and flow into open field drain.

7. Remove funnel and tube from collector box and replace collector box drain plug.

Figure 1 Priming Condensate Drain

Representative drawing only, some models may vary in appearance.

L11F065

Purge Gas Lines

If not previously done, purge the lines after all connections have been made and check for leaks.

4 440 04 4321 04

Specifications subject to change without notice.

Page 5

SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: (F/G)9MXT

! WARNING

FIRE OR EXPLOSION HAZARD

Failure to follow this warning could result in personal injury, death, and/or property damage.

Never purge a gas line into a combustion chamber. Never test for gas leaks with an open flame. Use a commercially available soap solution made specifically for the detection of leaks to check all connections. A fire or explosion may result causing property damage, personal injury or loss of life.

Adjustments

FIRE HAZARD

Failure to follow this warning could result in personal injury, death and/or property damage.

DO NOT bottom out gas valve regulator adjusting screw. This can result in unregulated manifold pressure and result in excess overfire and heat exchanger failures.

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)

Figure 2 Orifice Hole

For proper operation and long term reliability the furnace input rate must be within +/−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).

WARNING

CAUTION

BURNER

ORIFICE

A93059

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 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 LP/Propane conversion kit for instructions for setting gas manifold pressures for LP/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.

Table 1 Altitude Derate Multiplier for USA

ALTITUDE

FT. (M)

0–2000 (0−610)

2001–3000

(610−914)

3001–4000 (914−1219)

4001–5000

(1219−1524)

5001–6000

(1524−1829)

6001–7000

(1829−2134)

7001–8000

(2134−2438)

8001–9000

(2438−2743) 9001–10,000

(2743−3048)

* 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)

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.

PERCENT

OF DERATE

0 1.00

4−6 0.95

6−8 0.93

8−10 0.91

10−12 0.89

12−14 0.87

14−16 0.85

16−18 0.83

18−20 0.81

DERATE MULTIPLIER

FACTOR*

440 04 4321 04 5

Specifications subject to change without notice.

Page 6

SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: (F/G)9MXT

2. Obtain average yearly gas specific gravity from local gas supplier.

3. Find installation altitude 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.

FIRE HAZARD

Failure to follow this warning could result in personal injury, death, and/or property damage.

Re−install manifold pressure tap plug in gas valve to prevent gas leak.

14. Apply pipe dope sparingly to end of inlet gas pipe plug

WARNING

and re−install in the gas valve.

Adjust Manifold Pressure

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) for high heat, 1.4-in. w.c. (349 Pa) for low heat

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).

Check Inlet Gas Pressure

The inlet gas pressure must be checked with the furnace operating in maximum heat. This is necessary to make sure the inlet gas pressure does not fall below the minimum pressure of

4.5 in. w.c.

1. Make sure the gas supply is turned off to the furnace and at the electric switch on the gas valve.

2. Remove the 1/8 in. NPT plug from the inlet pressure tap on the gas valve.

3. Connect a manometer to the inlet pressure tap on gas valve.

4. Turn on furnace power supply.

5. Turn gas supply manual shutoff valve to ON position.

6. Turn furnace gas valve switch to ON position.

7. Jumper the R to W/W1 and W2 thermostat connections at the furnace control board.

8. When main burners ignite, confirm inlet gas pressure is between 4.5 in. w.c. (1125 Pa) and 13.6 in. w.c. (3388 Pa).

9. Remove jumper across thermostat connections to terminate call for heat. Wait until the blower off delay is completed.

10. Turn furnace gas valve electric switch to OFF position.

11. Turn gas supply manual shutoff valve to OFF position.

12. Turn off furnace power supply.

13. Remove manometer from the inlet pressure tap of the gas valve.

1. Adjust manifold pressure to obtain low fire input rate. (See Figure 3)

a. Turn gas valve ON/OFF switch to OFF. b. Remove manifold pressure tap plug from gas valve. c. Connect a water column manometer or similar device

to manifold pressure tap. d. Turn gas valve ON/OFF switch to ON. e. Move setup switch SW−1 (TT) on furnace control to

ON position to lock furnace in low−heat operation.

(See Figure 4 and Figure 15)

f. Manually close blower door switch.

g. Jumper R and W/W1 thermostat connections on

control to start furnace. (See Figure 4) h. Remove regulator adjustment cap from low heat gas

valve pressure regulator (See Figure 3) and turn

low−heat adjusting screw (3/16 or smaller flat−tipped

screwdriver) counterclockwise (out) to decrease input

rate or clockwise (in) to increase input rate.

NOTICE

DO NOT set low−heat manifold pressure less than 1.3−in. w.c. (324 Pa) or more than 1.7−in. w.c. (423 Pa) for natural gas. If required manifold pressure is outside this range, change main burner orifices.

Figure 3

1/2” NPT Inlet

1/8” NPT Inlet Pressure Tap

i. Install low−heat regulator adjustment cap. j. Move setup switch SW−1 (TT) to off position after

completing low−heat adjustment.

Redundant Automatic Gas Control Valve (2−Stage)

ON/OFF Switch

Regulator Seal Cap

Regulator Adjustment Regulator Seal Cap under Cap

1/8” NPT Manifold Pressure Tap

1/2” NPT Outlet

A11152

6 440 04 4321 04

Specifications subject to change without notice.

Page 7

SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: (F/G)9MXT

k. Leave manometer or similar device connected and

proceed to Step 2.

2. Adjust manifold pressure to obtain high fire input rate. (See Figure 3)

a. Jumper R to W/W1 and W2 thermostat connections

on furnace control. This keeps furnace locked in high−heat operation.

b. Remove regulator adjustment cap from high−heat

gas valve pressure regulator (See Figure 3) and turn high heat adjusting screw (3/16−in. or smaller flat−tipped screwdriver) counterclockwise (out) to decrease input rate or clockwise (in) to increase input rate.

NOTICE

DO NOT set high−heat manifold pressure less than 3.2−in. w.c. (797 Pa) or more than 3.8 in. w.c. (947 Pa) for natural gas. If required manifold pressure is outside this range, change main burner orifices to obtain manifold pressure in this range.

c. When correct input is obtained, replace caps that

conceal gas valve regulator adjustment screws. Main burner flame should be clear blue, almost

transparent. (See Figure 13) d. Reinstall manifold pressure tap plug to gas valve. e. Remove jumpers R to W/W1 and R to W2.

3. Verify natural gas input rate by clocking meter.

NOTE: Contact your HVAC distributor or gas supplier for metric gas meter Tables, if required.

a. Turn off all other gas appliances and pilots served by

the meter. b. Move setup switch SW−1 (TT) to ON position. This

keeps furnace locked in low−heat operation when

only W/W1 is energized. c. Jumper R to W/W1. d. Run furnace for 3 minutes in low−heat operation.

e. Measure time (in sec) for gas meter to complete one

revolution and note reading. The 2 or 5 cubic feet dial provides a more accurate measurement of gas flow.

f. Refer to Table 2 for cubic ft. of gas per hr.

g. Multiply gas rate cu ft./hr by heating value (Btuh/cu

ft.) to obtain input rate.

h. If clocked rate does not match required input from

Step 1, increase manifold pressure to increase input or decrease manifold pressure to decrease input. Repeat steps b through e of Step 1 until correct low−heat input is achieved. Re−install low heat regulator seal cap on gas valve.

i. Jumper R to W/W1, and W2. This keeps furnace

locked in high--heat operation when both W/W1 and W2 are energized.

j. Repeat items (d) through (h) for high-heat operation,

repeating Step 2 and adjusting the high-heat regulator screw, as required.

4. Restore furnace to normal operating condition. a. Turn gas valve ON/OFF switch to OFF. b. Remove water column manometer or similar device

from manifold pressure tap. c. Replace manifold pressure tap plug to gas valve. d. Turn gas valve ON/OFF switch to ON. e. Move setup SW-1 switch (TT) on furnace control to

position required for attached thermostat (OFF for

single-stage thermostats, ON for two-stage

thermostats).

f. Check for gas leaks and verify furnace operation.

FIRE HAZARD

Failure to follow this warning could result in personal injury, death, and/or property damage.

Re−install manifold pressure tap plug in gas valve to prevent gas leak.

WARNING

440 04 4321 04 7

Specifications subject to change without notice.

Page 8

SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: (F/G)9MXT

Figure 4 Example of Two−Stage Furnace Control Board

SET UP SWITCHES THERMOSTAT TYPE (TT) AND HEAT OFF−DELAY

SW1

OFF

COM

24V

Table 2

SECONDS G

FOR 1 REVOLUTION

Gas Rate (CU ft./hr)

SIZE OF TEST DIAL SECONDS

1 Cu Ft. 2 Cu Ft. 5 Cu Ft. 1 Cu Ft. 2 Cu Ft. 5 Cu Ft.

10 360 720 1800 50 72 144 360 11 327 655 1636 51 71 141 355

12 300 600 1500 52 69 138 346 13 277 555 1385 53 68 136 340

14 257 514 1286 54 67 133 333 15 240 480 1200 55 65 131 327 16 225 450 1125 56 64 129 321 17 212 424 1059 57 63 126 316 18 200 400 1000 58 62 124 310 19 189 379 947 59 61 122 305 20 180 360 900 60 60 120 300 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 97 243 28 129 257 643 76 47 95 237 29 124 248 621 78 46 92 231 30 120 240 600 80 45 90 225 31 11 6 232 581 82 44 88 220 32 11 3 225 563 84 43 86 214 33 109 218 545 86 42 84 209 34 106 212 529 88 41 82 205 35 103 206 514 90 40 80 200 36 100 200 500 92 39 78 196 37 97 195 486 94 38 76 192 38 95 189 474 96 38 75 188 39 92 185 462 98 37 74 184 40 90 180 450 100 36 72 180 41 88 176 439 102 35 71 178 42 86 172 429 104 35 69 173 43 84 167 419 106 34 68 170 44 82 164 409 108 33 67 167 45 80 160 400 11 0 33 65 164 46 78 157 391 11 2 32 64 161 47 76 153 383 11 6 31 62 155 48 75 150 375 120 30 60 150 49 73 147 367

8 440 04 4321 04

W2 Y1 DHUM G COM W/W1 Y/Y2 R

24−V THERMOS TAT TERMINALS

3−AMP FUSE

LED OPERATION & DIAGNOSTIC LIGHT

BLOWER SPEED TERMINALS

115−VAC (L2) NEUTRAL CONNECTIONS

24V

FUSE 3−AMP

COM

HI HT

COOL

LO H T

SPARE 2

SPARE 1

TEST / TWIN

COM/BLUE 24VAC/RED

24V MTR TAPS

EAC−2

FOR 1 REVOLUTION

Specifications subject to change without notice.

SW1

OFF

1 2 3

TT OFF DLY

PLT

HUM

24VAC

PL1

EAC TERMINAL 115 VAC 1.0 AMP MAX

115 VAC LINE (L1)

INPUT

TWINNING AND/OR COMPONENT TEST TERMINAL

11 5 VA C BLOWER POWER (BL1) CONNECTION

EAC−1

L1 BL−1 XFMR

HUMIDIFIER TERMINAL (24 VAC 0.5 AMPS MAX)

TRANSFORMER 24 VAC CONNECTIONS

P−1 LOW VOLTAGE

11 5 VA C TRANSFORMER PRIMARY

P2 − HOT SURFACE IGNITER/INDUCE R MOTOR CONNECTION

IDR

HSIR

PL2

HUM

115 VAC HUM

HSI HI LO

SIZE OF TEST DIAL

IHI/LOR

IDM

L12F037

Page 9

SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: (F/G)9MXT

Table 3 Orifice Size and Manifold Pressure (in. w.c.) for Gas Input Rate

TWO-STAGE FURNACE

(TABULATED DATA BASED ON 20,000 BTUH HIGH-HEAT / 13,000 BTUH LOW-HEAT PER BURNER,

DERATED 2%/1000 FT (305M) ABOVE SEA LEVEL)

ALTITUDE

RANGE

ft (m)

092543 3.6 / 1.5 43 3.7 / 1.6 43 3.8 / 1.6 42 3.2 / 1.4

(0) 950 43 3.4 / 1.4 43 3.5 / 1.5 43 3.6 / 1.5 43 3.7 / 1.6

to 1000 44 3.5 / 1.5 44 3.6 / 1.5 44 3.8 / 1.6 43 3.4 / 1.4

U.S.A. and CanadaU.S.A. On

y U.S.A. Only U.S.A. and Canada

U.S.A. On

2000 1050 44 3.2 / 1.3 44 3.3 / 1.4 44 3.4 / 1.4 44 3.5 / 1.5

(610) 1075 45 3.7 / 1.6 45 3.8 / 1.6 44 3.3 / 1.4 44 3.4 / 1.4

U.S.A. 800 42 3.4 / 1.4 42 3.5 / 1.5 42 3.6 / 1.5 42 3.7 / 1.6

2001 (611) 825 43 3.8 / 1.6 42 3.3 / 1.4 42 3.4 / 1.4 42 3.5 / 1.5

to 850 43 3.6 / 1.5 43 3.7 / 1.6 42 3.2 / 1.3 42 3.3 / 1.4

3000 (914) 875 43 3.4 / 1.4 43 3.5 / 1.5 43 3.7 / 1.5 43 3.8 / 1.6

Canada 925 44 3.5 / 1.5 44 3.6 / 1.5 44 3.8 / 1.6 43 3.4 / 1.4

2001 (611) 950 44 3.3 / 1.4 44 3.4 / 1.5 44 3.6 / 1.5 44 3.7 / 1.6

to 975 44 3.2 / 1.3 44 3.3 / 1.4 44 3.4 / 1.4 44 3.5 / 1.5

4500 (1372) 1000 46 3.8 / 1.6 45 3.8 / 1.6 44 3.2 / 1.4 44 3.3 / 1.4

3001 800 43 3.8 / 1.6 42 3.2 / 1.4 42 3.3 / 1.4 42 3.4 / 1.4

(915) 825 43 3.6 / 1.5 43 3.7 / 1.6 43 3.8 / 1.6 42 3.2 / 1.4

4000 900 44 3.4 / 1.4 44 3.5 / 1.5 44 3.7 / 1.5 44 3.8 / 1.6

(1219) 925 44 3.2 / 1.4 44 3.4 / 1.4 44 3.5 / 1.5 44 3.6 / 1.5

4001 775 43 3.7 / 1.6 43 3.8 / 1.6 42 3.3 / 1.4 42 3.4 / 1.4

(1220) 800 43 3.5 / 1.5 43 3.6 / 1.5 43 3.7 / 1.6 43 3.8 / 1.6

5000 875 44 3.3 / 1.4 44 3.5 / 1.5 44 3.6 / 1.5 44 3.7 / 1.6

(1524) 900 44 3.2 / 1.3 44 3.3 / 1.4 44 3.4 / 1.4 44 3.5 / 1.5

5001 750 43 3.7 / 1.5 43 3.8 / 1.6 42 3.2 / 1.4 42 3.3 / 1.4

(1525) 775 43 3.4 / 1.4 43 3.5 / 1.5 43 3.7 / 1.5 43 3.8 / 1.6

6000 850 44 3.3 / 1.4 44 3.4 / 1.4 44 3.5 / 1.5 44 3.6 / 1.5

(1829) 875 45 3.7 / 1.6 44 3.2 / 1.3 44 3.3 / 1.4 44 3.4 / 1.4

6001 700 42 3.2 / 1.3 42 3.3 / 1.4 42 3.4 / 1.4 42 3.5 / 1.5

(1830) 725 43 3.6 / 1.5 43 3.7 / 1.6 43 3.8 / 1.6 42 3.3 / 1.4

7000 800 44 3.4 / 1.4 44 3.5 / 1.5 44 3.6 / 1.5 44 3.7 / 1.6

(2133) 825 44 3.2 / 1.3 44 3.3 / 1.4 44 3.4 / 1.4 44 3.5 / 1.5

HEATVALUE0.580.600.620.64

AT ALTITUDE Orifice Mnfld Press Orifice Mnfld Press Orifice Mnfld Press Orifice Mnfld Press

(Btu/cu ft) No. High/Low No. High/Low No. High/Low No. High/Low

900 43 3.8 / 1.6 42 3.2 / 1.4 42 3.3 / 1.4 42 3.4 / 1.4

975 44 3.7 / 1.6 44 3.8 / 1.6 43 3.4 / 1.5 43 3.6 / 1.5

1025 44 3.3 / 1.4 44 3.5 / 1.5 44 3.6 / 1.5 44 3.7 / 1.6

1100 46 3.7 / 1.6 46 3.8 / 1.6 45 3.8 / 1.6 44 3.2 / 1.4

900 44 3.7 / 1.6 44 3.8 / 1.6 43 3.5 / 1.5 43 3.6 / 1.5

775 42 3.3 / 1.4 42 3.4 / 1.4 42 3.5 / 1.5 42 3.6 / 1.5

850 44 3.8 / 1.6 43 3.5 / 1.5 43 3.6 / 1.5 43 3.7 / 1.6

875 44 3.6 / 1.5 44 3.7 / 1.6 43 3.4 / 1.4 43 3.5 / 1.5

950 45 3.7 / 1.6 44 3.2 / 1.3 44 3.3 / 1.4 44 3.4 / 1.4

750 42 3.3 / 1.4 42 3.4 / 1.4 42 3.5 / 1.5 42 3.6 / 1.5

825 44 3.8 / 1.6 43 3.4 / 1.4 43 3.5 / 1.5 43 3.6 / 1.5

850 44 3.5 / 1.5 44 3.7 / 1.5 44 3.8 / 1.6 43 3.4 / 1.4

925 46 3.8 / 1.6 45 3.7 / 1.6 44 3.2 / 1.4 44 3.3 / 1.4

725 42 3.2 / 1.4 42 3.3 / 1.4 42 3.4 / 1.5 42 3.5 / 1.5

800 44 3.7 / 1.6 44 3.8 / 1.6 43 3.4 / 1.5 43 3.5 / 1.5

825 44 3.5 / 1.5 44 3.6 / 1.5 44 3.7 / 1.6 44 3.8 / 1.6

900 46 3.7 / 1.6 46 3.8 / 1.6 45 3.8 / 1.6 44 3.2 / 1.4

675 42 3.4 / 1.4 42 3.5 / 1.5 42 3.6 / 1.5 42 3.8 / 1.6

750 43 3.4 / 1.4 43 3.5 / 1.5 43 3.6 / 1.5 43 3.7 / 1.6

775 44 3.6 / 1.5 44 3.7 / 1.6 43 3.4 / 1.4 43 3.5 / 1.5

850 46 3.8 / 1.6 45 3.8 / 1.6 44 3.2 / 1.4 44 3.3 / 1.4

SAGLARUTANFOYTIVARGCIFICEPSSAG.GVA

A11252A

440 04 4321 04 9

Specifications subject to change without notice.

Page 10

SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: (F/G)9MXT

Table 3 (Cont.) Orifice Size and Manifold Pressure (in. w.c.) for Gas Input Rate

TWO-STAGE FURNACE

(TABULATED DATA BASED ON 20,000 BTUH HIGH-HEAT / 13,000 BTUH LOW-HEAT PER BURNER,

DERATED 2%/1000 FT (305M) ABOVE SEA LEVEL)

ALTITUDE

RANGE

ft (m)

7001 675 43 3.8 / 1.6 42 3.2 / 1.4 42 3.3 / 1.4 42 3.4 / 1.5

(2134) 700 43 3.5 / 1.5 43 3.7 / 1.5 43 3.8 / 1.6 42 3.2 / 1.4

8000 775 44 3.3 / 1.4 44 3.4 / 1.4 44 3.5 / 1.5 44 3.7 / 1.5

(2438) 800 45 3.8 / 1.6 44 3.2 / 1.4 44 3.3 / 1.4 44 3.4 / 1.4

8001 650 43 3.8 / 1.6 42 3.2 / 1.4 42 3.3 / 1.4 42 3.4 / 1.4

(2439) 675 43 3.5 / 1.5 43 3.6 / 1.5 43 3.7 / 1.6 42 3.2 / 1.3

U.S.A. OnlyU.S.A. Only U.S.A. Only

* Orifice numbers shown in BOLD are f actory-installed.

9000 750 44 3.3 / 1.4 44 3.4 / 1.4 44 3.5 / 1.5 44 3.6 / 1.5

(2743) 775 45 3.7 / 1.6 44 3.2 / 1.3 44 3.3 / 1.4 44 3.4 / 1.4

9001 600 42 3.3 / 1.4 42 3.4 / 1.5 42 3.6 / 1.5 42 3.7 / 1.6

(2744) 625 43 3.7 / 1.6 42 3.2 / 1.3 42 3.3 / 1.4 42 3.4 / 1.4

10000 700 44 3.4 / 1.4 44 3.5 / 1.5 44 3.7 / 1.5 44 3.8 / 1.6

(3048) 725 44 3.2 / 1.3 44 3.3 / 1.4 44 3.4 / 1.4 44 3.5 / 1.5

HEATVALUE0.580.600.620.64

AT ALTITUDE Orifice Mnfld Press Orifice Mnfld Press Orifice Mnfld Press Orifice Mnfld Press

(Btu/cu ft) No. High/Low No. High/Low No. High/Low No. High/Low

650 42 3.4 / 1.4 42 3.5 / 1.5 42 3.6 / 1.5 42 3.7 / 1.6

725 44 3.8 / 1.6 43 3.4 / 1.4 43 3.5 / 1.5 43 3.6 / 1.5

750 44 3.5 / 1.5 44 3.7 / 1.5 44 3.8 / 1.6 43 3.4 / 1.4

825 46 3.7 / 1.6 46 3.8 / 1.6 45 3.8 / 1.6 44 3.2 / 1.4

625 42 3.4 / 1.4 42 3.5 / 1.5 42 3.6 / 1.5 42 3.7 / 1.6

700 44 3.7 / 1.6 43 3.4 / 1.4 43 3.5 / 1.5 43 3.6 / 1.5

725 44 3.5 / 1.5 44 3.6 / 1.5 44 3.7 / 1.6 44 3.8 / 1.6

650 43 3.5 / 1.5 43 3.6 / 1.5 43 3.7 / 1.6 43 3.8 / 1.6

675 44 3.7 / 1.6 44 3.8 / 1.6 43 3.4 / 1.4 43 3.5 / 1.5

SAGLARUTANFOYTIVARGCIFICEPSSAG.GVA

A11252B

Adjust Temperature Rise

NOTE: Blower door must be installed when taking temperature

rise reading. Leaving blower door off will result in incorrect temperature measurements, due to possible changes in duct static pressure and airflow.

CAUTION

FURNACE DAMAGE HAZARD

Failure to follow this caution may result in:

S Overheating the heat exchangers or condensing

flue gases in heat exchanger areas not designed for condensate

S Shortened furnace life S Component damage

Temperature rise must be within limits specified on furnace rating plate. Recommended operation is at midpoint of rise range or slightly above.

Place SW−1 (TT) in ON position. Jumper R to W/W1 and W2 to check high−heat temperature rise. To check low−heat temperature rise, remove jumper to W2. Determine air temperature rise for both high and low−heat. Do not exceed temperature rise ranges specified on unit rating plate for high and low−heat.

This furnace must operate within the temperature rise ranges specified on the furnace rating plate. Determine the air temperature as follows:

1. Place duct thermometers in return and supply ducts as close to furnace as possible. Be sure thermometers do not “see” heat exchangers so that radiant heat does not affect thermometer readings. This is particularly important with straight run ducts.

2. When thermometer readings stabilize, subtract return−air temperature from supply−air temperature to determine temperature rise.

If the temperature rise is outside this range, check the following:

1. Gas input for low and high heat operation.

2. Derate for altitude if applicable.

3. Return and supply ducts for excessive restrictions causing static pressures greater than 0.50−in. w.c. (125 Pa)

4. Adjust temperature rise by adjusting blower speed.

S Increase blower speed to reduce temperature rise. S Decrease blower speed to increase temperature rise.

WARNING

ELECTRICAL OPERATION HAZARD

Failure to follow this warning could result in personal injury or death.

Disconnect 115vac electrical power before changing speed tap.

10 440 04 4321 04

Specifications subject to change without notice.

Page 11

SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: (F/G)9MXT

Table 4 Blower Speed Taps

COLOR SPEED

Gray 5 Cool

Yellow 4 Spare

Blue 3 HI HT

Orange 2 Spare

Red 1 LO HT/Cont Fan

For low−heat, the following connections can be made at LO HT on control:

FACTORY

ATTACHED TO:

S Orange blower motor lead S Red blower motor lead − Factory Setting

(Read following caution before changing taps.)

CAUTION

UNIT DAMAGE HAZARD

To avoid operating outside the rise range and avoid component damage:

Refer to the Air Delivery Tables to determine which airflows and settings are allowed for proper heating airflow. DO NOT use the highlighted settings for High−Stage Heating airflow. The highlighted settings are to be used for Low−Stage Heating and Cooling ONLY.

Change the blower speed taps as required to maintain proper temperature rise for Heating and Cooling as described above. To change blower motor speed selections for heating mode, remove blower motor lead from control HEAT terminal(s). (See Figure 4) Select desired blower motor speed lead(s) from the other motor leads and relocate it/them to LOW or HIGH HEAT terminal(s). Reconnect original lead on SPARE terminal

Adjust Blower Off Delay (Heat Mode)

If desired, the main blower off time delay period may be lengthened or shortened when operating in the heating mode to provide greater comfort. For position and location of switches on control center. (See Figure 4 and Figure 15)

a. Remove blower door if installed. b. Turn setup switches SW−2 and SW−3 ON or OFF for

desired blower off delay. See Table 5, Figure 4 and

Figure 15.

c. Proceed to “Set Blower Off Delay” before installing

blower door.

Table 5 Blower Speed Taps

DESIRED HEATING MODE

BLOWER OFF DELAY

(SEC.)

90 OFF OFF

120 OFF ON

150 ON OFF

180 ON ON

SETUP SWITCH

(SW-2 & SW-3)

POSITION

SW-2 SW-3

Adjust Continuous Fan Airflow

The Continuous Fan airflow can be set from the remaining blower speed taps. Refer to the Air Delivery Tables in these instructions.

The Continuous Fan speed can be changed to any other speed tap by toggling th Fan switch at the thermostat. See the Sequence of Operation for details.

CAUTION

FURNACE OVERHEATING HAZARD

Failure to follow this caution may result in reduced furnace life.

Recheck temperature rise. It must be within limits specified on the rating plate. Recommended operation is at the mid−point of rise range or slightly above.

Adjust Thermostat Heat Anticipator

Mechanical thermostat: Set thermostat heat anticipator to

match the amp. draw of the electrical components in the R-W/W1 circuit. Accurate amp. draw readings can be obtained at the wires normally connected to thermostat sub-base terminals, R and W. The thermostat anticipator should NOT be in the circuit while measuring current. (See Figure 5)

1. Set SW-1 (TT) switch on furnace control board to ON. (See Figure 4)

2. Remove thermostat from sub-base or from wall.

3. Connect an amp. meter across the R and W sub-base terminals or R and W wires at wall.

4. Record amp. draw across terminals when furnace is in low heat and after blower starts.

5. Set heat anticipator on thermostat per thermostat instructions and install on sub-base or wall.

6. Turn SW-1 (TT) switch OFF.

7. Install blower access door.

Electronic thermostat: Set cycle rate for 3 cycles per hr.

Figure 5 Amp. Draw Check with Ammeter

THERMOSTAT SUBBASE TERMINALS WITH THERMOSTAT REMOVED (ANITICIPATOR, CLOCK, ETC., MUST BE OUT OF CIRCUIT.)

HOOK-AROUND AMMETER

R Y W G

Adjust Cooling Airflow

The cooling airflow can be set from the remaining blower speed taps. Refer to the Air Delivery Tables in these instructions.

If a two−stage air conditioning or heat pump is installed, the Low Cooling Speed is the same speed tap as the Low Heat (LO HT), as well as Continuous Fan.

440 04 4321 04 11

EXAMPLE:

Specifications subject to change without notice.

10 TURNS

FROM UNIT 24-V CONTROL TERMINALS

5.0 AMPS ON AMMETER 10 TURNS AROUND JAWS

0.5 AMPS FOR THERMOSTAT

ANTICIPATOR SETTING

A96316

Page 12

SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: (F/G)9MXT

Table 6 AIR DELIVERY - CFM (with filter1)

UNIT SIZE

0401410 SIDE/BOTTOM

0601714 SIDE/BOTTOM

0801716 SIDE/BOTTOM

0802120

1002120

1202422

RETURN-AIR

CONNECTION

BOTTOM or

TWO-SIDES

BOTTOM or

TWO-SIDES

BOTTOM or

TWO-SIDES

SPEED

TAPS

Gray 1120 1080 1030 980 925 875 820 760 690 630

Yellow 880 845 810 780 740 710 680 640 615 570

Blue 695 665 620 575 535 495 455 420 370 280

Orange 640 595 540 495 460 420 370 310 260 230

Red 570 525 475 425 385 330 255 220 -

Gray 1720 1670 1620 1565 1505 1440 1375 1295 1220 1135

Yellow 1325 1285 1255 1220 1185 1145 1115 1075 1040 1000

Blue 1010 970 925 875 835 785 745 690 660 620

Orange 1160 1115 1080 1045 1000 960 920 875 840 785

Red 785 715 655 595 530 490 435 385 340 285

Gray 1810 1770 1720 1665 1610 1540 1475 1400 1315 1235

Yellow 1535 1500 1475 1435 1405 1370 1340 1310 1245 1160

Blue 1380 1340 1305 1270 1240 1200 1165 1130 1090 1050

Orange 1180 1130 1095 1060 1015 975 935 895 850 800

Red 1100 1045 1010 970 920 885 845 790 745 690

Gray 2290 2225 2155 2090 2015 1930 1845 1750 1640 1515

Yellow 1810 1760 1725 1685 1640 1600 1555 1520 1480 1415

Blue 1385 1340 1285 1240 1200 1140 1090 1050 995 950

4, 5

Orange 1560 1520 1475 1430 1385 1335 1295 1240 1200 1150

Red 1055 985 910 860 795 750 680 615 565 495

Gray 2340 2295 2250 2195 2110 2030 1935 1835 1725 1605

Yellow 1950 1900 1855 1800 1755 1705 1655 1605 1560 1485

Blue 1750 1700 1650 1605 1555 1500 1455 1395 1350 1300

4, 5

Orange 1570 1520 1460 1410 1350 1300 1240 1195 1140 1095

Red 1350 1280 1225 1155 1105 1045 1000 950 895 830

Gray 2275 2230 2185 2130 2055 1950 1825 1710 1610 1500

Yellow 1875 1820 1770 1720 1660 1600 1550 1505 1450 1390

Blue 2170 2125 2075 2025 1975 1900 1790 1695 1590 1470

4, 5

Orange 31475 1420 1350 1280 1215 1165 1105 1050 995 930

Red

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

1625 1565 1505 1445 1385 1325 1275 1225 1170 1130

NOTE:

1. A filter is required for each return−air inlet. Airflow performance includes a 3/4 in. (19 mm) washable filter media such as contained in factory−authorized accessory filter rack. See accessory list. To determine airflow performance without this filter, assume an additional 0.1 in. W.C. available external static pressure.

2. ADJUST THE BLOWER SPEED TAPS AS NECESSARY FOR THE PROPER AIR TEMPERATURE RISE FOR EACH INSTALLATION.

3. Shaded areas indicate that this airflow range is BELOW THE RANGE ALLOWED FOR HIGH−STAGE HEATING OPERATION. THESE AIRFLOW RANGES MAY ONLY BE USED FOR LOW−STAGE HEAT OR COOLING.

4. Airflows over 1800 CFM require bottom return, two−side return, or bottom and side return. A minimum filter size of 20” x 25” is required.

5. For upflow applications, air entering from one side into both the side of the furnace and a return air base counts as a side and bottom return.

6. The ”−” entry indicates an unstable operating condition.

Check Safety Controls

The flame sensor, gas valve, and pressure switch were all checked in the Start−up procedure section as part of normal operation.

1. Check Main Limit Switch This control shuts off combustion system and energizes air−circulating blower motor, if furnace overheats. By using this method to check the temperature limit control, it can be established that the limit is functioning properly and that the limit will operate if there is a restricted return−air supply or motor failure. If the limit control does not function during this test, the cause must be determined and corrected.

a. Run furnace for at least 5 minutes. b. Gradually block off return air with a piece of

cardboard or sheet metal until the limit trips.

c. Unblock return air to permit normal circulation.

d. Burners will re−light when furnace cools down.

2. Check Pressure Switch(es) This control proves operation of the draft inducer blower.

a. Turn off 115−V power to furnace. b. Disconnect inducer motor lead wires from wire

harness.

c. Turn on 115−V power to furnace.

d. Set thermostat to “call for heat” and wait 1 minute.

When pressure switch is functioning properly, hot surface igniter should NOT glow and control diagnostic light flashes a status code 3. If hot surface igniter glows when inducer motor is disconnected, shut down furnace immediately.

e. Determine reason pressure switch did not function

properly and correct condition.

EXTERNAL STATIC PRESSURE (IN.W.C.)

f. Turn off 115−V power to furnace.

g. Reconnect inducer motor wires, replace outer door,

and turn on 115−V power.

h. Blower will run for 90 seconds before beginning the

call for heat again.

i. Furnace should ignite normally.

Checklist

1. Put away tools and instruments. Clean up debris.

2. Verify that the jumper is removed from the TEST/TWIN terminal. Verify that there is nothing plugged into the PLT connector.

NOTE: Note: If there is a jumper connector plugged into PLT, remove it and discard. (See Figure 14)

3. Verify that Heating Operating Mode switch SW−1 is set properly.. (See Figure 14)

4. Verify that the Blower/Heat Off−Delay SW−2 and SW−3 switches are set as desired. (See Figure 14)

5. Verify that the blower (lower door in upflow position) and control (“Main” or upper door in upflow position) doors are properly installed.

6. Verify that the Status LED glows. If not, check that the power supply is energized and that the blower door is secure. (See Figure 14) to interpret diagnostic codes.

7. Cycle test furnace with room thermostat to be sure that it operates properly with the room thermostat. Check all modes including Heat, Cool and Fan.

8. Check operation of accessories per manufacturer’s instructions.

9. Review Home Owner’s Information with owner.

10. Attach entire literature packet to furnace.

12 440 04 4321 04

Specifications subject to change without notice.

Page 13

SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: (F/G)9MXT

SERVICE AND MAINTENANCE PROCEDURES

FIRE, INJURY OR DEATH HAZARD

Failure to follow this warning could result in personal injury, death and/or property damage.

The ability to properly perform maintenance on this equipment requires certain knowledge, mechanical skills, tools, and equipment. If you do not possess these, do not attempt to perform any service and maintenance on this equipment other than those procedures recommended in the Owner’s Manual.

ENVIRONMENTAL HAZARD

Failure to follow this caution may result in environmental pollution.

Remove and recycle all components or materials (i.e. oil, refrigerant, control board, etc.) before unit final disposal.

WARNING

CAUTION

Figure 6 Multipoise Orientations

Electrical Controls and Wiring

ELECTRICAL SHOCK HAZARD

Failure to follow this warning could result in personal injury or death.

There may be more than one electrical supply to the furnace. Check accessories and cooling unit for additional electrical supplies that must be shut off during furnace servicing. Lock out and tag switch with a suitable warning label.

WARNING

A93041

ELECTRICAL SHOCK, FIRE OR EXPLOSION HAZARD

Failure to follow this warning could result in personal injury or death, or property damage.

Before installing, modifying, or servicing system, main electrical disconnect switch must be in the OFF position and install a lockout tag. There may be more than one disconnect switch. Lock out and tag switch with a suitable warning label. Verify proper operation after servicing.

ELECTRICAL OPERATION HAZARD

Failure to follow this caution may result in improper furnace operation or failure of furnace.

Label all wires prior to disconnection when servicing controls. Wiring errors can cause improper and dangerous operation.

WARNING

CAUTION

General

These instructions are written as if the furnace is installed in an upflow application. An upflow furnace application is where the blower is located below the combustion and controls section of the furnace, and conditioned air is discharged upward. Since this furnace can be installed in any of the 4 positions shown in Figure 6, you must revise your orientation to component location accordingly.

The electrical ground and polarity for 115−V wiring must be properly maintained. Refer to Figure 7 for field wiring information and to Figure 15 for furnace wiring information.

NOTE: If the polarity is not correct, the STATUS LED on the control will flash code 10 and prevent the furnace from heating. The control system also requires an earth ground for proper operation of the control and flame−sensing electrode.

The 24−V circuit contains an automotive−type, 3−amp. fuse located on the control. (See Figure 4) Any shorts of the 24−V wiring during installation, service, or maintenance will cause this fuse to blow. If fuse replacement is required, use ONLY a 3−amp. fuse. The control LED display will be off when fuse needs to be replaced.

Troubleshooting

Refer to the service label. (See Figure 14—Service Label) The Troubleshooting Guide − Flow Chart (See Figure 16) can

be a useful tool in isolating furnace operation problems. Beginning with the word “Start,” answer each question and follow the appropriate arrow to the next item.

The Guide − Flow Chart will help to identify the problem or failed component. After replacing any component, verify correct operation sequence.

Proper instrumentation is required to service electrical controls. The control in this furnace is equipped with a Status Code LED (Light−Emitting Diode) to aid in installation, servicing, and troubleshooting. Status codes can be viewed at the indicator in blower door. The green furnace control LED is either be a heartbeat, off, or a code composed of 1 or 2 digits. The first digit is the number of short flashes, the second digit is the number of long flashes.

440 04 4321 04 13

Specifications subject to change without notice.

Page 14

SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: (F/G)9MXT

Figure 7 Heating and Cooling Application Wiring Diagram with Single−Stage Thermostat

FIELD 24-VOLT WIRING FIELD 115-, 208/230-, 460-VOLT WIRING FACTORY 24-VOLT WIRING FACTORY 115-VOLT WIRING

BLK

WHT

GND

115-VOLT FIELD-

SUPPLIED

FUSED

DISCONNECT

BLK

WHT

JUNCTION BOX

FIVE

WIRE

THREE-WIRE

HEATING-

ONLY

CONTROL

BOX

FURNACE

COM

W/W1

Y/Y2

24-VOLT

TERMINAL

BLOCK

NOTE 2

WC Y RG

NOTE 1

NOTES: 1.

Connect Y/Y2-terminal as shown for proper operation.

Some thermostats require a "C" terminal connection as shown.

If any of the original wire, as supplied, must be replaced, use same type or equivalent wire.

1-STAGE THERMOSTAT TERMINALS

CONDENSING

UNIT

FIELD-SUPPLIED

FUSED DISCONNECT

GND

208/230- OR 460-VOLT THREE PHASE

208/230VOLT SINGLE PHASE

A95236

For an explanation of status codes, refer to service label located on control door or Figure 14, and the troubleshooting guide which can be obtained from your distributor.

Retrieving Stored Fault Codes

NOTE: Fault codes cannot be retrieved if a thermostat signal

(24-V on W, Y, G, etc.) is present, or if any delays such as blower off-delays are active.

The stored status codes will NOT be erased from the control memory when 115- or 24-V power is interrupted. See the Service Label (See Figure 14) for more information. The most recent fault code may be retrieved as follows:

1. Leave 115-V power connected to furnace.

2. Observe the status LED through the blower door (the lower door on upflow applications) indicator. Refer to the Service Label (See Figure 14) to interpret the LED.

3. Remove the Main/Control door (the upper door on upflow installations).

4. BRIEFLY (2−3 seconds) disconnect and reconnect ONE of the main limit wires.

5. The LED will flash the last stored fault code. Refer to the Service Label (See Figure 14) to interpret the 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 valve and humidifier terminal HUM 24 VAC are not energized. The EAC-1 terminal is energized when the blower is energized. The HUM terminal is energized when the inducer is energized. This feature helps diagnose a system problem in case of a component failure. The component test feature will not operate if any thermostat signal is present at the control and not until all time delays are completed.

To begin Component Self−Test:

1. Remove blower access door.

2. Disconnect the thermostat R lead from furnace control.

3. Manually close blower door switch.

Caution must be taken when manually closing this switch for service purposes.

WARNING

ELECTRICAL SHOCK HAZARD

Failure to follow this warning could result in personal injury, or death.

Blower access door switch opens 115−V power to control. No component operation can occur unless switch is closed. Caution must be taken when manually closing this switch for service purposes.

4. For approximately 2 sec, short (jumper) the C terminal on control to the TEST/TWIN 3/16—in. (5 mm) quick-connect terminal on control until the LED goes off. Remove jumper from terminals. (See Figure 4)

NOTE: If TEST/TWIN and C terminals are jumpered longer than 2 sec., LED will flash code 10 and ignore component test request.

Component test sequence is as follows:

a. LED will display previous status code 4 times. b. Inducer motor starts and continues to run until Step g

of component test sequence.

c. After 7 seconds the hot surface igniter is energized for

15 sec., then off. d. Blower motor operates on LO−HT speed for 10 sec. e. Blower motor operates on HI−HT speed for 10 sec.

f. Blower motor operates on COOL speed for 10 sec.

g. Inducer motor goes to low speed for 10 sec., then stops.

5. Reconnect R lead to furnace control, remove tape from blower door switch, and re-install blower door.

6. Verify furnace shut down by lowering thermostat setting below room temperature.

7. Verify that furnace restarts by raising thermostat setting above room temperature.

14 440 04 4321 04

Specifications subject to change without notice.

Page 15

SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: (F/G)9MXT

8. Release blower door switch, reattach wire to “R” terminal on furnace control board and replace blower door.

Care and Maintenance

FIRE OR EXPLOSION HAZARD

Failure to follow this warning could result in personal injury, death and/or property damage.

Never store flammable or combustible materials on, near, or in contact with the furnace, such as:

1. Spray or aerosol cans, rags, brooms, dust mops, vacuum cleaners, or other cleaning tools.

2. Soap powders, bleaches, waxes or other cleaning compounds, plastic or plastic containers, gasoline, kerosene, cigarette lighter fluid, dry cleaning fluids, or other volatile fluids.

3. Paint thinners and other painting compounds, paper bags, or other paper products. Exposure to these materials could lead to corrosion of the heat exchangers.

For continuing high performance and to minimize possible furnace failure, periodic maintenance must be performed on this furnace. Consult your local dealer about proper frequency of maintenance and the availability of a maintenance contract.

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 electrical supplies to the furnace and install lockout tag before performing any maintenance or service. Follow the operating instructions on the label attached to the furnace.

CARBON MONOXIDE POISONING AND FIRE HAZARD

Failure to follow this warning could result in personal injury, death and/or property damage.

Never operate furnace without a filter or filtration device installed. Never operate a furnace with filter or filtration device access doors removed.

CUT HAZARD

Failure to follow this caution may result in personal injury.

Sheet metal parts may have sharp edges or burrs. Use care and wear appropriate protective clothing, safety glasses and gloves when handling parts, and servicing furnaces.

The minimum maintenance on this furnace is as follows:

1. Check and clean air filter each month or more frequently if required. Replace if torn.

2. Check blower motor and wheel for cleanliness each heating and cooling season. Clean as necessary.

WARNING

CAUTION

3. Check electrical connections for tightness and controls for proper operation each heating season. Service 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. Inspect the vent pipe/vent system before each heating season for water leakage, sagging pipes or broken fittings. Have vent pipes/vent system serviced by a qualified service agency.

6. Inspect any accessories attached to the furnace such as a humidifier or electronic air cleaner. Perform any service or maintenance to the accessories as recommended in the accessory instructions.

Cleaning and/or Replacing Air Filter

The air filter type may vary depending on the application or orientation. The filter is external to the furnace casing. There are no provisions for an internal filter with this furnace. See “Filter Arrangement” under the “Installation” section of this manual.

NOTE: If the filter has an airflow direction arrow, the arrow must point toward the blower. To clean or replace filters, proceed as follows:

ELECTRICAL SHOCK, FIRE OR EXPLOSION HAZARD

Failure to follow this warning could result in personal injury or death, or property damage.

1. Turn off electrical supply to furnace.

2. Remove filter cabinet door.

3. Slide filter out of cabinet.

4. If equipped with permanent, washable filter, clean filter by spraying cold tap water through filter in opposite direction of airflow. Rinse filter and let dry. Oiling or coating of the filter is not recommended.

5. If equipped with factory specified disposable media filter, replace only with a factory specified media filter of the same size.

6. Slide filter into cabinet.

7. Replace filter cabinet door.

8. Turn on electrical supply to furnace.

WARNING

Blower Motor and Wheel Maintenance

To ensure long life, economy, and high efficiency, clean accumulated dirt and grease from blower wheel and motor annually.

The inducer and blower motors are pre−lubricated and require no additional lubrication. These motors can be identified by the absence of oil ports on each end of the motor.

The following items should be performed by a qualified service technician. Clean blower motor and wheel as follows:

1. Turn off electrical supply to furnace.

2. Remove blower door.

3. All factory wires can be left connected, but field thermostat and accessory wiring may need to be disconnected depending on their length and routing.

440 04 4321 04 15

Specifications subject to change without notice.

Page 16

SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: (F/G)9MXT

4. If the vent and combustion air pipe passes through the blower compartment, it will be necessary to remove the pipes from the blower compartment.

Disconnect the vent and combustion air pipe by:

a. Loosen the clamps on the vent couplings and

combustion air pipe external to the furnace.

b. Separate the pipes from the couplings and move

them aside.

c. Loosen the clamps on the vent couplings and

combustion air pipe located on the blower shelf.

d. Separate the pipes from the blower compartment and

set aside.

e. Remove the couplings from the pipe adapters and set

aside.

f. After servicing the blower, reverse steps a through e.

g. Tighten all clamps 15 lb−in.

See Figure 8 for steps 5 through 14.

5. Remove screws securing blower assembly to blower shelf and slide blower assembly out of furnace. Detach ground wire and disconnect blower motor harness plugs from blower motor.

NOTE: Blower wheel is fragile. Use care.

6. Clean blower wheel and motor by using a vacuum with soft brush attachment. Be careful not to disturb balance weights (clips) on blower wheel vanes. Do not bend wheel or blades as balance will be affected.

7. If greasy residue is present 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. Loosen setscrew holding blower wheel on motor

shaft. NOTE: Mark blower mounting arms and blower housing so each arm is positioned at the same hole location during reassembly.

c. Mark blower wheel orientation and cutoff plate

location to ensure proper reassembly.

d. Remove screws securing cutoff plate and remove

cutoff plate from housing.

e. Remove bolts holding motor mounts to blower

housing and slide motor and mounts out of housing.

f. Remove blower wheel from housing.

g. Clean wheel per instructions on degreaser cleaner.

Do not get degreaser in motor.

8. Reassemble motor and blower wheel by reversing items 7b through 7f. Ensure wheel is positioned for proper rotation.

9. Torque motor mounting bolts to 40 +/− 10 lb−in. when reassembling.

10. Torque blower wheel set screw to 160 +/− 20 lb−in. when reassembling.

11. Verify that blower wheel is centered in blower housing and set screw contacts the flat portion of the motor shaft. Loosen set screw on blower wheel and reposition if necessary.

12. Spin the blower wheel by hand to verify that the wheel does not rub on the housing.

13. Reinstall blower assembly in furnace.

14. Reinstall 2 screws securing blower assembly to blower deck.

15. Reconnect blower leads to furnace control. Refer to furnace wiring diagram, and connect thermostat leads if previously disconnected.

NOTE: Be sure to attach ground wire and reconnect blower harness plugs to blower motor.

Figure 8 Blower Assembly

MOTOR SHAFT FLAT

SET SCREW

GROMMET

MOTOR ARM

SCREW LOCATION

BLO HSG ASSY

BRACKET

BRACKET ENGAGEMENT

DETAIL A

SEE DETAIL A

CUTOFF, BLOWER

WHEEL, BLOWER

BRACKET

POWER CHOKE

OR CAPACITOR

WHEN REQUIRED

SCREW

(GND)

MOTOR WHEEL HUB

A11584A

SCREW

A11584B

A11584C

A11584D

BLOWER HSG ASSY

MOTOR, BLOWER

A11584E

16 440 04 4321 04

Specifications subject to change without notice.

Page 17

SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: (F/G)9MXT

6. Remove individual wires from terminals on gas valve.

ELECTRICAL OPERATION HAZARD

Failure to follow this warning could result in personal injury or death.

Blower door switch opens 115−V power to control. No component operation can occur unless switch is closed. Caution must be taken when manually closing this switch for service purposes.

16. Downflow or horizontal furnaces with vent pipe through furnace only:

a. Install and connect short piece of vent pipe inside

furnace to existing vent.

b. Connect vent connector to vent elbow.

17. Turn on electrical supply. Manually close blower door switch. Use a piece of tape to hold switch closed. Check for proper rotation and speed changes between heating and cooling by jumpering R to G and R to Y/Y2 on furnace control thermostat terminals. If outdoor temperature is below 70_F (21_C), turn off circuit breaker to outdoor unit before running furnace in the cooling cycle. Turn outdoor circuit breaker on after completing cooling cycle. (See Figure 4)

NOTE: If R−W/W1 thermostat terminals are jumpered at the time blower door switch is closed, blower will run for 90 sec before beginning a heating cycle.

a. Perform component self−test as shown at the bottom

of the SERVICE label, located on the control door.

b. Verify blower is rotating in the correct direction

18. If furnace is operating properly, RELEASE BLOWER DOOR SWITCH. Remove any jumpers or reconnect any disconnected thermostat leads. Replace blower door.

19. Turn on gas supply and cycle furnace through one complete heating cycle. Verify the furnace temperature rise as shown in Adjustments Section. Adjust temperature rise as shown in Adjustments Section.

WARNING

Cleaning Burners and Flame Sensor

The following items must be performed by a qualified service technician. If the burners develop an accumulation of light dirt or dust, they may be cleaned by using the following procedure:

NOTE: Use a back-up wrench on the gas valve to prevent the valve from rotating on the manifold 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 electrical supplies to the furnace and install lockout tag before performing any maintenance or service. Follow the operating instructions on the label attached to the furnace.

Refer to Figure 9.

1. Disconnect power at external disconnect, fuse or circuit breaker.

2. Turn off gas at external shut-off or gas meter.

3. Remove control door and set aside.

4. Turn electric switch on gas valve to OFF.

5. Disconnect the gas pipe from gas valve and remove pipe from the furnace casing.

WARNING

7. Disconnect Hot Surface Igniter (HSI) wires from HSI.

8. Disconnect Flame Sensor wire from Flame Sensor.

9. Support the manifold and remove the four screws that secure the manifold assembly to the burner assembly and set aside. Note the location of the green/yellow wire and ground terminal.

10. Inspect the orifices in the manifold assembly for blockages or obstructions. Remove orifice and clean or replace orifice.

11. Remove the four screws that attach the top plate of the casing to the furnace.

12. Raise top plate up slightly and prop it up with a small piece of wood or folded cardboard.

13. Support the burner assembly and remove the screws that attach the burner assembly to the heat exchanger cell panel.

14. Remove wires from both rollout switches.

15. Slide one−piece burner out of slots on sides of burner assembly.

16. Remove the flame sensor from the burner assembly.

17. (Optional) Remove the Hot Surface Igniter (HSI) and bracket from the burner assembly.

18. Check igniter resistance. Nominal resistance is 40 to 70 ohms at room temperature and is stable over the life of the igniter.

19. Clean burner with a brush and a vacuum.

20. Clean the flame sensor with fine steel wool (0000 grade). Do not use sand paper or emery cloth.

Figure 9 Burner Assembly

BURNER SUPT. ASSY

BURNER ASSY

FLAME ROLL−OUT SWITCH

FLAME SENSOR

(

BELOW BURNER)

Representative drawing only, some models may vary in appearance.

To reinstall burner assembly:

1. Install the Hot Surface Igniter (HSI) and bracket in burner assembly.

2. Install flame sensor on burner.

3. Align the edges of the one-piece burner with the slots in the burner assembly and slide the burners forward until they are fully seated in the burner assembly.

4. Align the orifices in the manifold assembly with the support rings on the end of the burner.

5. Insert the orifices in the support rings of the burners.

NOTE: If manifold does not fit flush against the burner, do not force the manifold on the burner assembly. The burners are not fully seated forward in the burner assembly. Remove the manifold and check burner positioning in the burner assembly assembly before re-installing the manifold.

L11F064

440 04 4321 04 17

Specifications subject to change without notice.

Page 18

SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: (F/G)9MXT

6. Attach the green/yellow wire and ground terminal to one of the manifold mounting screws.

7. Install the remaining manifold mounting screws.

8. Check the igniter alignment. See Figure 9, Figure 10 and Figure 11.

Figure 10 Igniter Position − Top View

1-1/4-in.

(31.8)

2-1/2-in.

(64.4)

A11405

Figure 11 Igniter Position − Side View

2ïin. 50 mm

3/8ïin.

9.6 mm

3/16ïin.

4.6 mm

+ 1/32

1/10ïin.

ï 1/16ïin.

+0.8

2.5 mm ï1.5 mm

L12F041

9. Attach the wires to the roll-out switches.

10. Align the burner assembly with the openings in the primary cell inlet panel and attach the burner assembly to the cell panel.

11. Connect the wire for the flame sensor.

12. Connect the wire for the Hot Surface Igniter.

NOTE: Use propane-resistant pipe dope to prevent leaks. Do not use Teflon tape.

13. Install the gas pipe to the gas valve.

FIRE OR EXPLOSION HAZARD

Failure to follow this warning could result in personal injury, death, and/or property damage.

14. Check for gas leaks with a commercially available soap solution made specifically for the detection of leaks.

WARNING

15. Turn gas on at electric switch on gas valve and at external shut-off or meter

16. Turn power on at external disconnect, fuse or circuit breaker.

17. Run the furnace through two complete heating cycles to check 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, Figure 10 and Figure 11.

1. Turn off gas and electrical supplies to furnace.

2. Remove control door.

3. Disconnect igniter wire connection.

4. Check igniter resistance. Igniter resistance is affected by temperature. Only check resistance when the igniter is at room temperature.

a. Using an ohm meter, check resistance across both

igniter leads in connector.

b. Cold reading should be between 40 ohms and 70

ohms.

5. Remove igniter assembly. a. Using a 1/4−in. driver, remove the two screws

securing the igniter mounting bracket to the burner assembly (See Figure 9)

b. Carefully withdraw the igniter and bracket assembly

through the front of the burner assembly without

striking the igniter on surrounding parts. c. Inspect igniter for signs of damage or failure. d. If replacement is required, remove the screw that

secures the igniter on igniter bracket and remove the

igniter.

6. To replace igniter and bracket assembly, reverse items 5a through 5d.

7. Reconnect igniter harness to the igniter, dressing the igniter wires to ensure there is no tension on the igniter itself. (See Figure 9)

8. Turn on gas and electrical supplies to furnace.

9. Verify igniter operation by initiating control board self−test feature or by cycling thermostat.

10. Replace control door.

Flushing Collector Box and Drainage System

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 electrical supplies to the furnace and install lockout tag before performing any maintenance or service. Follow the operating instructions on the label attached to the furnace.

1. Turn off gas and electrical supplies to furnace.

2. Remove control door.

3. Disconnect pressure switch tube from pressure switch port.

NOTE: Ensure the pressure switch tube disconnected from the pressure switch is higher than the collector box opening or water will flow out of tube.

4. Remove the collector box plug from the top port on the upper corner of the collector box. (See Figure 1)

WARNING

18 440 04 4321 04

Specifications subject to change without notice.

Page 19

SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: (F/G)9MXT

5. Attach a funnel with a flexible tube to port on the collector box.

6. Flush inside of collector box with water until discharge water from condensate trap is clean and runs freely.

7. Repeat steps 4 thru 6 with middle plug on upper corner of collector box.

8. Remove the pressure switch tube from the collector box.

NOTE: Do NOT blow into tube with tube connected to the pressure switch.

9. Clean pressure switch port on collect box with a small wire. Shake any water out of pressure switch tube.

10. Reconnect tube to pressure switch and pressure switch port.

11. Remove the relief tube from the port on the collector box and the trap.

12. Clean the relief port on collect box and the trap with a small wire. Shake any water out of the tube.

13. Reconnect relief tube to trap and collector box ports.

Cleaning Condensate Drain and Trap

NOTE: If the condensate trap is removed, a new gasket

between the trap and collector box is required. Verify a condensate trap gasket is included in the service kit or obtain one from your local distributor.

1. Disconnect power at external disconnect, fuse or circuit breaker.

2. Turn off gas at external shut-off or gas meter.

3. Remove control door and set aside.

4. Turn electric switch on gas valve to OFF.

5. Disconnect external drain from condensate drain elbow or drain extension pipe inside the furnace and set aside.

6. Disconnect the condensate trap relief hose from collector box port and condensate trap.

NOTE: If condensate has a heat pad attached to the trap, trace the wires for the pad back to the connection point and disconnect the wires for the heat pad.

7. Remove the screw that secures the condensate trap to the collector box, remove the trap and set aside.

8. Remove the trap gasket from the collector box if it did not come off when the trap was removed.

9. Discard the old trap gasket.

10. Rinse condensate trap in warm water until trap is clean.

11. Flush condensate drain lines with warm water. Remember to check and clean the relief port on the collector box.

12. Shake trap dry.

13. Clean port on collector box with a small wire.

To re-install Condensate Drain and Trap:

1. Remove adhesive backing from condensate trap gasket

2. Install gasket on collector box

3. Align the condensate trap with the drain opening on the collector box and secure the trap with the screw

4. Attach the relief hose to the relief port on the condensate trap and collector box.

5. Secure tubing to prevent any sags or traps in the tubing.

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 drain extension pipe.

9. Turn gas on at electric switch on gas valve and at external shut-off or meter

10. Turn power on at external disconnect, fuse or circuit breaker.

440 04 4321 04 19

11. Run the furnace through two complete heating cycles to check for proper operation

12. Install control door when complete.

Checking Heat Pad Operation (If Applicable)

In applications where the ambient temperature around the furnace is 32_F (0_C) or lower, freeze protection measures are required. If this application is where heat tape has been applied, check to ensure it will operate when low temperatures are present.

NOTE: The Heat Pad, when used, should be wrapped around the condensate drain trap. There is no need to use heat tape within the furnace casing. Most heat tapes are temperature activated, and it is not practical to verify the actual heating of the tape. Check the following:

1. Check for signs of physical damage to heat tape such as nicks, cuts, abrasions, gnawing by animals, etc.

2. Check for discolored heat tape insulation. If any damage or discolored insulation is evident, replace heat tape.

3. Check that heat tape power supply circuit is on.

Cleaning Heat Exchangers

The following items must be performed by a qualified service technician.

Primary Heat Exchangers

If the heat exchangers get an accumulation of light dirt or dust on the inside, they may be cleaned by the following procedure:

NOTE: If the heat exchangers get a heavy accumulation of soot and carbon, both the primary and secondary heat exchangers should be replaced rather than trying to clean them thoroughly due to their intricate design. A build−up of soot and carbon indicates that a problem exists which needs to be corrected, such as improper adjustment of manifold pressure, insufficient or poor quality combustion air, improper vent termination, incorrect size or damaged manifold orifice(s), improper gas, or a restricted heat exchanger (primary or secondary). Action must be taken to correct the problem.

1. Turn off gas and electrical supplies to furnace.

2. Remove control door.

3. Disconnect wires or connectors to flame rollout switch, gas valve, igniter, and flame sensor.

4. Using backup wrench, disconnect gas supply pipe from furnace gas control valve.

5. Remove two screws attaching top filler plate and rotate upwards to gain access to screws attaching burner assembly to cell panel.

6. Remove screws attaching burner assembly to cell panel. (See Figure 9)

NOTE: Burner cover, manifold, gas valve, and burner assembly should be removed as one assembly.

7. Clean heat exchanger openings with a vacuum and a soft brush. (See Figure 12)

Specifications subject to change without notice.

Page 20

SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: (F/G)9MXT

Figure 12 Cleaning Heat Exchanger Cell

NOTE: After cleaning, inspect the heat exchangers to ensure

they are free of all foreign objects that may restrict flow of combustion products.

8. Reverse items 6 through 1 for reassembly.

9. Refer to furnace wiring diagram and reconnect wires to flame rollout switch, gas valve, igniter, and flame sensor.

10. Turn on gas and electrical supplies to furnace.

11. Check furnace operation through two complete heat operating cycles. Look at burners. Burner flames should be clear blue, almost transparent. (See Figure 13)

Figure 13 Burner Flame

Burner Flame

Burner

Manifold

A11461

FIRE OR EXPLOSION HAZARD

Failure to follow this warning could result in personal injury, death, and/or property damage.

12. Check for gas leaks.

13. Replace main furnace door.

Secondary Heat Exchangers

The condensing side (inside) of the secondary heat exchanger CANNOT be serviced or inspected without complete removal of

WARNING

the heat exchanger assembly. Detailed information on heat exchanger removal can be obtained from your Distributor.

Winterization

CAUTION

UNIT AND PROPERTY DAMAGE HAZARD

Failure to follow this caution may result in unit component or property damage.

If the furnace is installed in an unconditioned space where the ambient temperatures may be 32_ F (0_ C) or lower, freeze protection measures must be taken to prevent property or product damage.

Since the furnace uses a condensing heat exchanger, some water will accumulate in the unit as a result of the heat transfer process. Therefore, once it has been operated, it cannot be turned off and left off for an extended period of time when temperatures will reach 32_F (0_C) or lower unless winterized. Follow these procedures to winterize your furnace:

CAUTION

UNIT COMPONENT DAMAGE HAZARD

Failure to follow this caution may result in damage to the furnace and other property damage.

Do not use ethylene glycol (automotive antifreeze coolant or equivalent). Failure of plastic components may occur.

1. Obtain propylene glycol (RV/swimming pool antifreeze or equivalent).

2. Turn off gas and electrical supplies to your furnace.

3. Remove furnace control door.

4. Remove the top unused rubber plug from the port on the collector box opposite the condensate trap. (See Figure 1)

5. Connect a field supplied 3/8−in. (9.5−mm) ID tube to the open port on the collector box

6. Insert a field supplied funnel into the tube.

7. Pour 1 quart of anti−freeze solution into the funnel/tube. Antifreeze should run through the collector box, overfill condensate trap and flow to an open drain.

8. Replace the rubber plug in the port on the collector box.

9. Remove the middle unused rubber plug from the port on the collector box opposite the condensate trap. (See Figure 1)

10. Repeat Steps 5 through 8.

11. If a condensate pump is used, check with pump manufacturer to verify pump is safe for use with antifreeze used. Allow pump to start and pump anti−freeze to open drain.

12. Replace main door.

13. When furnace is re−started, flush condensate pump with clear water to check for proper operation before re−starting furnace.

14. Propylene glycol need not be removed before re−starting furnace.

20 440 04 4321 04

Specifications subject to change without notice.

Page 21

SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: (F/G)9MXT

Figure 14 Service Label

440 04 4321 04 21

338313−2F

Specifications subject to change without notice.

Page 22

SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: (F/G)9MXT

Figure 15 Wiring Diagram

22 440 04 4321 04

338313−2F

Specifications subject to change without notice.

Page 23

SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: (F/G)9MXT

Is LED status light ON solid, alt ernately

flashing bright

heartbeat, or flashing ON a nd OFF?

Is there 24V at 24VAC and COM?

Is there 115V at L1 and NE UTRAL?

Is the 24V fuse open?

Is door switch closed?

Replace transformer.

Replace door switch.

Is there 115V going to s witch?

Close the door switch.

Is circuit breaker closed?

Check for continuity in wire from circuit

breaker to furnace.

Close circuit breaker and go back to

START.

Is LED status light alternatel y flashing

bright

Determine status code. The status co de

is a

first

determined by the number of

short flashes and the seco

after the plus (+) sign

number of long

flashes?

To recall a status code: Briefly (2 – 3

seconds)

connect the TEST/TWIN terminal

to the “C” thermostat terminal with a j umper

wire

to begin status code re covery and

component test. If a previous status code is

present, the code will re peat 4 times then

go on to component test. If n o previous

code is present, a component test will

begin without flashi

ng any status codes.

Component Test Sequence: Gas valve

and humidifier will not be turned on.

Inducer motor will start in HIGH speed and

remain on HIGH until the en d of the blower

test, then shift to LOW speed for 7 to 15

seconds, the following compo nents

are on

for 10

– 15 seconds each individuall y: hot

surface igniter,

blower speeds: LO HEAT,

HI HEAT, COOL.

Was there a previous status code?

Go to section below for the flash ed status

code.

Does the control respond to W /W 1, W2,

Y1, Y/Y2, and G (24V

) thermostat

signals?

Run system through a low-heat, high-

heat, or cooling cycle to check operation.

Status codes are erased after 72 hours.

Is 24V present at W/W1, W 2, Y1, Y/Y2 or

G thermostat terminals on the furnace

control? Check room thermostat or

interconnecting cable.

Disconnect all the thermostat wire s from

the furnace control. Does the problem repeat when using a

jumper wire? Replace furnace control.

The thermostat is not compatible with the

furnace control. Either install a ballast

resistor, connect the

C furnace control

thermostat terminal to the thermostat, or

replace the thermostat.

YES

START

YES

Troubleshooting Guide

Replace furnace control.

YES

Is LED status light ON solid?

YES

The control is locked out an d will auto-

reset after 1 hour. Lockout could be due

to any of the following: - Flame sense circuit failure.

- Gas valve relay stuck open.

- Software check error.

Reset power to clear lockout. Replac e

control if code repeats.

Inspect secondary voltage (24V) wiring,

including thermostat leads f or short

circuit. Replace fuse

Figure 16 Troubleshooting Guide − Flow Chart

-dim-bright-dim like a

440 04 4321 04 23

Specifications subject to change without notice.

nd number

, the

-dim-bright-dim like a h eartbeat? number

single or two digit num ber with the

Page 24

SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: (F/G)9MXT

1 + 2 BLOWER ON AFTER POWER UP –

W/W1 opens)

6 + 1 IGNITION LOCKOUT – System failed to

ignite gas and prove flame in 4

attempts. Control will auto -

reset after 3

hours. Refer to status cod e #6.

5 ABNORMAL FLAME-PROVING SIGNAL

Flame is proved while gas valve is de-

energized. Inducer will run until fault is

cleared. Check for:

- Stuck open or leaky gas valve.

2 PRESSURE SWITCH DID NOT OPEN –

- Pressure switch stuck closed.

3 LOW-HEAT PRESSURE SW ITCH DID

NOT CLOSE OR REOPENED – If opens

during blower on-delay period, blower will

come on for the selected blower off-del ay.

If open longer than 5 minutes inducer

shuts off for 15 minutes before retry.

Check for:

- Proper vent sizing.

- Air leak between vestibule and blowe

compartment. - Low inlet gas pressure (if L GPS used).

- Disconnected or obstructed pressure

tubing.

Defective or miswired pressure s witches

- Excessive wind.

- Plugged condensate drain

- Water in vent piping, possible sagging pipe

- Restricted vent.

- Defective Inducer motor.

- Low inducer voltage (115 VAC)

4 LIMIT CIRCUIT FAULT – Indicates the

limit, flame rollout is open. Blo wer will run

for 4 min. or until open switch remakes

whichever is longer. If open lon ger than 3

min, code changes to lockout #7. If o pen

less than 3 min. status code #4 continues

to flash until blower shuts off. Flame

rollout switch requires manual reset.

Check for:

- Loose blo wer wheel.

- Defective switch or connections.

- Dirty filter or restricted duct system.

- Improper gas input adjustment

Improper limit switch or no limit gasket.

Unplug igniter harness from co ntrol and

repeat component

test. Check for 115V

between

connector P2 (HSI) a nd

NEUTRAL-L2 on the control. Was 115V

present for the 15 second period?

Check connections and retry.

If current

is near typical value

(4.0

-6.0μA DC nominal) and

burners will not stay on,

repeat check in high

-heat. If

burners will still not stay on

replace control. If burners

operate in high

-heat then

switch to low-heat, check

manifold pressure. If OK,

check burner carryover and

flame sensor location.

Clean flame sensor with fine steel wool

and recheck current. Nominal current is

4.0 to 6.0

Is current near typical value?

Replace electrode.

Will main burners ignite and stay on?

Replace furnace control.

Fixed.

YES

Replace furnace control.

Check for continuity in the

harness and igniter. Replac e

defective component.

Reconnect the R thermostat lea d and set

thermostat to call for hea

voltmeter across gas valve connections.

Does gas valve receive 24V?

Does gas valve open and allo w gas to

flow?

Do the main burners ignite?

Do the main burners stay on?

Allow blower to come on and

repeat test to check for

intermittent operation.

Check connections. If OK,

replace control.

Check for:

Inadequate flame carryover

Repeat call for heat and check flame

sensor current during trial for ignition

peri

YES

6 IGNITION PROVING FAILURE – If fla me is

not sensed during the trial for ignition

period, the control will repeat the ignition

sequence 3 more times before lockout #6 +

1 occurs. If flame signal is lost during the

blower on-delay period, blower will come on

for the selected blower off- delay. Check

the following before going to the next step. - Gas valve turned off.

- Manual shut-off valve open?

Green/Yellow wire MUST be connected

to furnace sheet metal.

- Flame sensor must not be grou nded.

9 HIGH-HEAT PRESSURE SWITCH OR

RELAY DID NOT CLOSE OR

REOPENED - Check for:

- Control rel ay may be defective.

- Gas v alve is miswired.

- Refe r to status code #3.

10 POLARITY – Check for correct line

7 LIMIT CIRCUIT LOCKOUT – Lockout

occurs if the limit or flame rollout is open

longer than 3 minutes. Control will auto-

reset after 3 hours. Refer to status code

#4.

8 GAS HEATING LOCKOUT – Control will

NOT auto reset. Turn off power and wait

Stuck closed gas valve relay on control.

- Mis wire or short to gas valve wire.

YES

Check that gas valve electri c

switch is turned

on. Replace

valv

To determine whether the p roblem is in

the gas valve, igniter, or flame sensor the

system can be operated in component

test mode. To check the igniter, remove

the R ther

mostat connection from the

control, reset power, start the component

test. Does the igniter glow o range/white

by the end of the 15 seco nd warm

-up

period?

YES

Figure 16 (CONT.) Troubleshooting Guide − Flow Chart

or rough ignition.

Low inlet gas pressure. - Proper firing rate.

t. Connect

μA DC.

od. Is the DC current below 0.5μA

Check for:

- Obstructed pressure tube.

24 440 04 4321 04

5 minutes to retry. Check for: -

Specifications subject to change without notice.

voltage polarity. If units are twinned,

(115V OR 24V) – Normal operation.

Blower runs for 90 seconds, if unit is

powered up during a call for heat (R-

W/W1 closed) or when (R-

check for proper low-voltag e (24V)

transformer phasing.

during the blower on-delay period.

Page 25

SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: (F/G)9MXT

Sequence of Operation

NOTE: Furnace control must be grounded for proper operation

or control will lockout. Control is grounded through green wire connected to gas valve and burner bracket screw. Using the schematic diagram in Figure 15, follow the sequence of operation through the different modes. Read and follow the wiring diagram very carefully.

NOTE: If a power interruption occurs during a call for heat (W/W1 or W/W1−and−W2), the control will run the blower for the selected heat off−delay period two seconds after power is restored, if the thermostat is still calling for gas heating. The green LED light will flash a status code 1+2 during this period, after which the LED will switch to a heartbeat, as long as no faults are detected. After this period, the furnace will respond to the thermostat normally.

The blower door must be installed for power to be conducted through the blower door interlock switch ILK to the furnace control CPU, transformer TRAN, inducer motor IDM, blower motor BLWM, hot−surface igniter HSI, and gas valve GV.

Two−Stage Heating with Single−Stage Thermostat

NOTE: The thermostat type switch (TT) selects either the

two−stage thermostat operation mode when ON, (see item 2) or the single stage thermostat operation mode when OFF in response to a call for heat. When the W2 thermostat terminal is energized it will always cause high−heat operation when the R to W circuit is closed, regardless of the setting of the thermostat type switch. This furnace can operate as a two−stage furnace with a single−stage thermostat because the furnace control CPU includes a programmed sequence of controlled operation, which selects low−heat for the first 12 minutes of operation then switches to high heat operation.

If the power is interrupted, the control CPU will operate in low heat for 12 minutes then it will switch to high−heat, as long as the thermostat continues to call for heat.

The wall thermostat “calls for heat”, closing the R to W circuit. The furnace control performs a self−check, verifies the low−heat and high−heat pressure switch contacts LPS and HPS are open, and starts the inducer motor IDM in high−speed. The HUM terminal is energized for a 115V humidifier (if used).

a. Inducer Prepurge Period (see Figure 15 schematic

diagram)

(1.) Low heat (W/W1) the inducer motor IDM comes up

to high−speed, the low−heat pressure switch LPS closes. After the low−heat pressure switch closes the furnace control CPU will begin a 15−second prepurge period, and continue to run the inducer motor IDM at high−speed.

(2.) High Heat (W/W1+W2) the inducer motor IDM

comes up to high speed and the high−heat pressure switch relay HPSR is de−energized to close the NC contact. When sufficient pressure is available, the high−heat pressure switch HPS closes, and the high−heat gas valve solenoid GV−HI is energized. After LPS closes, 24VAC power is supplied for a field−installed humidifier at the HUM 24VAC terminal and the furnace control CPU begins a 15−second prepurge period. If the high−heat pressure switch HPS fails to close and the low−heat pressure switch LPS closes, the furnace will operate at low−heat gas flow rate until the high−heat pressure switch closes for a maximum of 2 minutes after ignition. If HPS doesn’t close after 2 minutes from LPS closing, GV is turned off and heat off delay is completed. Then a new cycle will begin if a call for heat remains.

b. Igniter Warm

the (Hot Surface Igniter) HSI is energized for a 17−second igniter warm−up period.

−Up−At the end of the prepurge period,

c. Trial−for−Ignition Sequence−When the igniter

warm−up period is completed the main gas valve relay contacts GVR close to energize the gas valve solenoid GV−M, the gas valve opens. The gas valve solenoid GV−M permits gas flow to the burners where it is ignited by the HSI. 5 sec after the GVR closes, a 2−sec flame proving period begins. The HSI igniter will remain energized until the flame is sensed or until the 2−sec flame proving period begins. If the furnace control CPU operates in high−heat operation, the high−heat gas valve solenoid GV−HI is also energized.

d. Flame−Proving−When the burner flame is proved at

the flame−proving sensor electrode FSE, the inducer motor IDM switches to low−speed unless running at high−heat, and the furnace control CPU begins the blower−ON delay period and continues to hold the gas valve GV−M open. If the burner flame is not proved within two seconds, the control CPU will close the gas valve GV−M, and the control CPU will repeat the ignition sequence for up to three more Trials−For−Ignition before going to Ignition− Lockout. Lockout will be reset automatically after three hours, or by momentarily interrupting 115 vac power to the furnace, or by interrupting 24 vac power at 24VAC or COM to the furnace control CPU (not at W/W1, G, R, etc.). If flame is proved when flame should not be present, the furnace control CPU will lock out of Gas−Heating mode and operate the inducer motor IDM on high speed until flame is no longer proved.

e. Blower On Delay−If the burner flame is proven, the

blower on delay for low−heat and high−heat are as follows: Low−Heat−45 seconds after the gas valve GV− energized the blower motor (BLWM) is energized at LO HEAT speed. High−Heat−25 seconds after the gas valve GV−M is energized the BLWM is energized at HI HEAT speed. Simultaneously, the electronic air cleaner (EAC) terminal is energized and remains energized as long as the BLWM is energized.

f. Switching from Low−to High−Heat−If the furnace

control CPU switches from low−heat to high−heat, the furnace control CPU will switch the inducer motor IDM speed from low to high. The high−heat pressure switch relay HPSR is de−energized to close the NC contact. When sufficient pressure is available the high−heat pressure switch HPS closes, and the high−heat gas valve solenoid GV−HI is energized. The blower motor BLWM will switch to HI HEAT speed 5 seconds after the furnace control CPU switches from low−heat to high−heat.

g. Switching from High− to Low−Heat−The furnace

control CPU will not switch from high−heat to low−heat while the thermostat R−to−W circuit is closed when using a single stage thermostat.

h. Heat−Off Delay−When the thermostat is satisfied, the

R to W circuit is opened, de−energizing the gas valve GV−M, stopping gas flow to the burners, and de−energizing the humidifier terminal HUM 24VAC. The inducer motor IDM will remain energized for a 15−second post−purge period then turn off, also turning off HUM for 115V humidifier. The blower motor BLWM and air cleaner terminal EAC will remain energized for 90, 120, 150, or 180 seconds (depending on selection at heat−off delay switches). The furnace control CPU is factory−set for a 120−second heat

−off delay.

M is

440 04 4321 04 25

Specifications subject to change without notice.

Page 26

SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: (F/G)9MXT

15. Two−Stage Thermostat and Two−Stage Heating (See Figure 17 − Figure 22 for thermostat connections)

NOTE: In this mode the TT switch (SW1−1) must be ON to

select the two−stage thermostat mode in response to closing the thermostat R−to−W1 circuit. Closing the thermostat R−to−W1−and−W2 circuits always causes high−heat operation, regardless of the setting of the thermostat type. The wall thermostat “calls for heat”, closing the R−to−W1 circuit for low−heat or closing the R−to−W1 and−W2 circuits for high−heat. The furnace control performs a self−check, verifies the low−heat and high−heat pressure switch contacts LPS and HPS are open, and starts the inducer motor IDM in high−speed. The start up and shut down functions and delays described in item 1. above apply to the two−stage heating mode as well, except for switching from low− to high−heat and vice versa.

a. Switching from Low− to High−Heat−If the thermostat

R−to− W1 circuit is closed and the R−to−W2 circuit closes, the furnace control CPU will switch the inducer motor IDM speed from low to high. The high−heat pressure switch relay HPSR is de−energized to close the NC contact. When sufficient pressure is available the high

−heat pressure switch HPS closes, and the high−heat gas valve solenoid GV−HI is energized. The blower motor BLWM will switch to HI HEAT speed five seconds after the R−to−W2 circuit closes.

b. Switching from High− to Low−Heat−If the thermostat

R−to−W2 circuit opens, and the R−to−W1 circuit remains closed, the furnace control CPU will switch the inducer motor IDM speed from high to low. The high−heat pressure switch relay HPSR is energized to open the NC contact and de−energize the high−heat gas valve solenoid GV−HI. When the inducer motor IDM reduces pressure sufficiently, the high−heat pressure switch HPS will open. The gas valve solenoid GV−M will remain energized as long as the low−heat pressure switch LPS remains closed. The blower motor BLWM will switch to LO HEAT speed 5 seconds after the R−to−W2 circuit opens.

16. Cooling Mode−The thermostat “calls for cooling.” a. Single−Speed Cooling−

(See Figure 17 − Figure 22 for thermostat connections) The thermostat closes the R−to−G−and−Y circuits. The R−to−Y circuit starts the outdoor unit, and the furnace control R−to−G−and−Y/Y2 circuits start the furnace blower motor BLWM on cool speed. The electronic air cleaner terminal EAC is energized with 115 vac when the blower motor BLWM is operating.

When the thermostat is satisfied, the R−to−G and−Y circuits are opened. The outdoor unit will stop, and the furnace blower motor BLWM will continue operating on the COOL speed for an additional 90 seconds. Jumper Y/Y2 to DHUM to reduce the cooling off−delay to 5 seconds. (See Figure 4)

b. Two−Speed Cooling

The thermostat closes the R−to−G−and−Y1 circuits for low−cooling or closes the R−to−G−and−Y1−and−Y2 circuits for high−cooling. The R−to−Y1 circuit starts the outdoor unit on low−cooling speed, and the furnace control R−to−G−and−Y1 circuit starts the furnace blower motor BLWM on low−cool speed (same speed as LO HEAT). The R−to−Y1−and−Y2 circuits start the outdoor unit on high−cooling speed, and the furnace control R−to−G−and−Y1 and −Y2 circuits start the furnace blower motor BLWM on COOL speed. The electronic air cleaner terminal EAC is energized with 115 vac whenever the blower motor BLWM is operating. When the thermostat is satisfied, the R−to−G−and−Y1 or R−

to−G−and−Y1−and−Y2 circuits are opened. The outdoor unit stops, and the furnace blower BLWM and electronic air cleaner terminal EAC will remain energized for an additional 90 seconds. Jumper Y1 to DHUM to reduce the cooling off−delay to 5 seconds. (See Figure 4)

17. Dehumidify Mode (See Figure 17 − Figure 22 for humidity sensing thermostat connections) The dehumidification output, H on the humidity sensing thermostat should be connected to the furnace control thermostat terminal DHUM. When there is a dehumidify demand, the DHUM input is activated, (24 vac signal is removed from the H input terminal). In other words, the DHUM input logic is reversed. The DHUM input is turned ON when no dehumidify demand exists.

Activation/Deactivation

Once 24 vac is detected by the furnace control on the DHUM input, the furnace control operates enables the dehumidify mode. If the DHUM input is off for more than 48 hours, the furnace control disables the dehumidify mode. The cooling operation described in item 3. above also applies to operation with a humidity sensing thermostat. The exceptions are listed below: a. Low cooling − When the R−to−G−and−Y1 circuit is

closed and there is a demand for dehumidification,the furnace blower motor BLWM will continue running at low−cool speed (same speed as LO HEAT).

b. High cooling −When the R−to−G−and−Y/Y2 circuit is

closed and there is a demand for dehumidification,the furnace blower motor BLWM will drop the blower speed from COOL to HI HEAT for a maximum of 10 minutes before reverting back to COOL speed. If there is still a demand for dehumidification after 20 minutes, the furnace control CPU will drop the blower speed back to HI HEAT speed. This alternating 10−minute cycle will continue as long as there is a call for cooling.

c. Cooling off−delay − When the “call for cooling” is

satisfied and there is a demand for dehumidification, the cooling blower−off delay is decreased from 90 seconds to 5 seconds.

18. Continuous Blower Mode When the R−to−G circuit is closed by the thermostat, the blower motor BLWM will operate on continuous−blower speed LO HEAT speed. Terminal EAC is energized as long as the blower motor BLWM is energized. During a call for heat, the blower BLWM will stop during igniter warm−up (17 seconds), ignition (7 seconds), and blower−ON delay (45 seconds in low−heat, and 25 seconds in high−heat), allowing the furnace heat exchangers to heat up more quickly, then restarts at the end of the blower−ON delay period at LO HEAT or HI HEAT speed respectively. The blower motor BLWM will revert to continuous−blower speed after the heating cycle is completed. In high−heat, the furnace control CPU will hold the blower motor BLWM at HI HEAT speed during the selected blower−OFF delay period before reverting to continuous−blower speed. When the thermostat “calls for low−cooling”, the blower motor BLWM will operate at low−cool speed (same speed as LO HEAT). When the thermostat “calls for high−cooling”, the blower motor BLWM will operate at COOL speed. When the thermostat is satisfied, the blower motor BLWM will operate an additional 90 seconds on COOL speed before reverting back to continuous−blower speed. When the R−to−G circuit is opened, the blower motor BLWM will continue operating for an additional 5 seconds, if no other function requires blower motor BLWM operation.

19. Heat Pump (See Figure 17 − Figure 22 for thermostat connections) When installed with a heat pump, the furnace control automatically changes the timing sequence to avoid long blower off times during demand defrost cycles. When the R−to−W/W1−and−Y1 or R−to−W/W1−and−Y1−and−G circuits are energized the furnace control CPU will switch to or turn on the blower motor BLWM at low−cool speed

26 440 04 4321 04

Specifications subject to change without notice.

Page 27

SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: (F/G)9MXT

(same speed as LO HEAT), and begin a low−heat cycle. The blower motor BLWM will remain on until the end of the prepurge period, then shut off for 24 seconds then come back on at LO HEAT speed. When the W/W1 input signal disappears, the furnace control begins a normal inducer post−purge period and the blower remains running at LO HEAT speed. If the R−to− W/W1−and−Y1−and−G signals disappear at the same time, the blower motor BLWM will remain on for the selected heat−off delay period. If the R−to−W/W1−and−Y1 signals disappear, leaving the G signal, the blower motor BLWM will remain on for the selected heat−off delay period then switch to continuous−blower speed. When the R−to−W/W1−and−Y/Y2, R−to−W/W1−and− Y/Y2− and−G, R−to−W/W1−and−Y1−and−Y/Y2, or R−to−W/W1−and− Y1−and−Y/Y2−and−G circuits are energized the furnace control CPU will switch to or turn on the blower motor BLWM at COOL speed, and begin a high−heat cycle. The blower motor BLWM will remain on until the end of the prepurge period, then shut off for 24 seconds then come back on at HI HEAT speed. When the W/W1 input signal disappears, the furnace control begins a normal inducer post−purge period and the blower switches to COOL speed after a 3 second delay. If the R−to−W/W1

−and−Y/Y2−and−G or R−to−W/W1−and−Y1−and− Y/Y2−and−G signals disappear at the same time, the blower motor BLWM will remain on for the selected heat−off delay period. If the R−to−W/W1−and−Y/Y2 or R−to−W/W1− and−Y1−and−Y/Y2 signals disappear, leaving the G signal, the blower motor BLWM will remain on for the selected heat−off delay period then switch to continuous−blower speed.

Component Self Test

Refer to page 14 for instructions.

Figure 17

Two−Stage Furnace with Single−Speed Air Conditioner

Figure 18

NOTE 9

Figure 19

NOTE 9

Two−Stage Furnace with Two−Stage Air Conditioner

Two−Stage Furnace with Single−Stage Heat Pump (Dual Fuel)

NOTE 9

440 04 4321 04 27

Specifications subject to change without notice.

Page 28

SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: (F/G)9MXT

Figure 20

NOTE 9

Two−Stage Furnace with Two−Stage Heat Pump (Dual Fuel)

Figure 22

HP with Two−Stage Furnace, Humidifier, and Dehumidification

Figure 23 Two−Stage Furnace and Humidifier Only

Figure 21

For Figure 17 − Figure 22

1. Refer to outdoor equipment Installation Instructions for additional information and setup procedure.

2. Outdoor Air Temperature Sensor must be attached in all dual fuel application.

3. Refer to ICP thermostat Installation Instructions for additional information and setup procedure.

4. When using a Humidity Sensing Thermostat, set DEHUMIDIFY OPTIONS to H DE−ENRGZD FOR DEHUM

5. Optional connection for Two−Stage: If wire is connected, SW1−1(TT) on furnace control should be set to ON position to allow ICP Thermostat to control the furnace staging.

6. HUM 24VAC terminal is 24 VAC and is energized when the low pressure switch closes during a call for heat.

7. When connecting 115 VAC to humidifier use a separate 115 VAC supply.

8. When using a humidifier on a HP installation, connect humidifier to hot water.

9. Thermostat signals may vary. Consult thermostat installation instructions for more information.

AC with Two−Stage Furnace, Humidifier, and Dehumidification

28 440 04 4321 04

Specifications subject to change without notice.

Page 29

SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: (F/G)9MXT

Specifications subject to change without notice.

440 04 4321 04 29

PARTS REPLACEMENT INFORMATION GUIDE

Casing Group

Control door Blower door Top filler plate Bottom filler plate Door Knob Assembly

Electrical Group

Control box Junction box Limit switch(es) Circuit board Door switch Transformer 3−Amp fuse Flame Rollout switch Main Wiring harness Blower Motor harness (when used)

Filter Group

Filter(s)

Blower Group

Cut−off Plate Blower housing Blower motor Blower wheel Capacitor (when used) Capacitor strap (when used) Power choke (where used)

Gas Control Group

Manifold Burner Orifice Flame sensor Hot surface igniter Gas valve

Heat Exchanger Group

Primary Heat Exchanger assembly Primary Heat Exchanger cell panel Secondary Heat Exchanger assembly Coupling box Containment Plate Tubing Gaskets

Inducer Group

Pressure switch(es) Inducer assembly Inducer Inducer motor Motor Module (when used) Inducer motor capacitor (when used) Collector 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, personal injury, death or property damage. Improper installation, adjustment, alteration, service, maintenance, or use can cause carbon monoxide poisoning, explosion, fire,

electrical shock, or other conditions which may cause personal injury or property damage. Consult a qualified installer, service agency, local gas supplier, or your distributor or branch for information or assistance. The qualified installer or agency must use only factory-authorized and listed kits or accessories when modifying this product.

Have available the product/model number and the serial number located on the unit rating plate to ensure correct replacement parts.

TO OBTAIN INFORMATION ON PARTS: Consult your installing dealer or the classified section of your local telephone directory under the “Heating Equipment“ or “Air Conditioning Contractors and Systems” headings for dealer listing by brand name.

Page 30

SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: (F/G)9MXT

Specifications subject to change without notice.

30 440 04 4321 04

PRODUCT NOMENCLATURE

DIGIT POSITION

1 2 3 4 5 6, 7, 8 9, 10 11, 12 13 14

9 M X T 060 17 14 A 1

G = Mainline Look 1 F = Mainline Look 2 N = Entry 9 = 90% − 100% EFFICIENCY M = Multiposition H = Horizontal U = Upflow D = Downflow

FEATURE

A = Modulating Variable Speed ECM V = Variable 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 L = Low Nox

FEATURE

040 = 40,000 BTU/hr 060 = 60,000 BTU/hr 080 = 80,000 BTU/hr 100 = 100,000 BTU/hr 120 = 120,000 BTU/hr

INPUT HEAT

14 = 14−3/16” 17 = 17−1/2” 21 = 21” 24 = 24−1/2”

CABINET WIDTH

10 = 1000 CFM (max) 14 = 1400 CFM (max) 16 = 1600 CFM (max) 20 = 2000 CFM (max) 22 = 2200 CFM (max)

COOLING AIRFLOW

SALES (MAJOR) REVISION DIGIT ENGINEERING (MINOR) REVISION DIGIT

International Comfort Products, LLC

Consumer Relations Department

P.O. Box 128

Lewisburg, TN 37091, USA

931−270−4100

ICP F9MXT1002120A, F9MXT0601714A, F9MXT0801716A, F9MXT0802120A, F9MXT1202422A Service And Technical Support Manual

Specifications and Main Features

Frequently Asked Questions

User Manual