Troubleshooting guide

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troubleshooting guide

355MAV

Variable Speed, Two-Stage Series H & I

Electronic Condensing 355AAV

Gas Furnace 355BAV

Cancels: SM05-5 SM05-07

6-08

INDEX

PAGE

Safety Considerations................................................................................. 1

Instructions.................................................................................................. 1

Example ...................................................................................................... 2

General........................................................................................................ 2

Sequence of Operation ............................................................................... 2

Single-Stage Thermostat and Two-Stage Heating (Adaptive

Mode) ................................................................................................. 2

Two-Stage Thermostat and Two-Stage Heating .............................. 4

Cooling Mode .................................................................................... 4

Single-Speed Cooling ........................................................................ 4

Single-Stage Thermostat and Two-Speed Cooling (Adaptive

Mode) ................................................................................................. 4

Two-Stage Thermostat and Two-Speed Cooling ............................. 5

Thermidistat Mode............................................................................. 5

Super-Dehumidify Mode................................................................... 5

Continuous-Blower Mode ................................................................. 6

Heat Pump Defrost............................................................................. 6

Component Test................................................................................. 6

Service/Status Code Instructions ............................................................... 7

Start Here .................................................................................................... 9

Rapid Flashing AMBER LED................................................................. 10

Improper Cooling Air Flow ..................................................................... 11

High Heat Temperature Rise Too Low ................................................... 12

Status Code 11 - No Previous Code......................................................... 13

Status Code 12 - Blower On After Power Up ......................................... 13

Status Code 13 - Limit Circuit Lockout .................................................. 14

Status Code 14 - Ignition Lockout ........................................................... 15

Status Code 15 – Blower Motor Lockout................................................ 15

Status Code 21 - Gas Heating Lockout.................................................... 15

Status Code 22 - Abnormal Flame-Proving Signal................................. 16

Status Code 23 - Pressure Switch Did Not Open .................................... 16

Status Code 24 - Secondary Voltage Fuse Is Open................................. 17

Status Code 25 – Model Selection or Setup Error................................... 19

Status Code 31 – High-Heat Switch or Relay did not close or

Reopen.............................................................................................. 19

Status Code 32 - Low-Heat Pressure Switch Did Not Close or

Reopened.......................................................................................... 21

Status Code 33 - Limit Circuit Fault........................................................ 23

Status Code 34 - Ignition-Proving Fault.................................................. 25

Status Code 41 – Blower Motor Fault ..................................................... 26

Status Code 42 – Inducer Motor Fault..................................................... 28

Status Code 43 - Low-Heat Pressure Switch Open While High-Heat

Pressure Switch Is Closed................................................................ 30

Status Code 45 – Control Circuitry Lockout........................................... 31

Cleanup and Start-Up Instructions........................................................... 31

APPENDIX A - Board Layout & Wiring Schematic ............................. 32

APPENDIX B - ECM Blower Motor Description & Operation............ 36

APPENDIX C - Pressure Check Diagram .............................................. 37

APPENDIX D - Static Pressure Reading Location Diagrams................ 38

APPENDIX E - Quick Reference Information ....................................... 40

APPENDIX F - Furnace Staging Algorithm........................................... 41

SAFETY CONSIDERATIONS

Installing and servicing heating equipment can be hazardous due to

gas and electrical components. Only trained and qualified personnel

should install, repair, or service heating equipment.

Untrained personnel can perform basic maintenance functions such as

cleaning coils, or cleaning and replacing filters. All other operations

should be performed by trained service personnel. When working on

heating equipment, observe precautions in literature, on tags, and on

labels attached to or shipped with the unit, and other safety

precautions that may apply.

Follow all safety codes. In the United States, follow all safety codes

including the National Fuel Gas Code (NFGC) NFPA 54-2006/ANSI

Z223.1-2006. In Canada, refer to the National Standard of Canada

Natural Gas and Propane Installation Codes (NSCNGPIC), CSA

B149.1-05.

Wear safety glasses and work gloves. Have a fire extinguisher

available during start-up, adjustment procedures, and service calls.

Recognize safety information. This is the safety-alert symbol .

When you see this symbol on the furnace and in instructions or

manuals, be alert to the potential for personal injury.

Understand the signal words DANGER, WARNING, and CAUTION,

and NOTE. The words DANGER, WARNING, and CAUTION 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.

INSTRUCTIONS

This guide uses your expertise and observations to lead you to the

trouble spot as efficiently as possible. This is only intended as a guide

and should not be used blindly. Your experience and expertise are of

high value when troubleshooting this unit. Do not disregard all of

your instincts.

The variable speed furnace control was designed with diagnostic

capabilities built in. A AMBER LED is used to flash a status code

which will lead you to one of the sections as listed in the Index.

You should ALWAYS begin in the START HERE section (see Index

for page number) which will guide you to the appropriate section

where a minimal number of steps will be used to correct the problem.

Once in a section, read the ACTION. An ACTION may have a

Summary of content (44 pages)

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troubleshooting guide 355MAV Series H & I 355AAV 355BAV Variable Speed, Two-Stage Electronic Condensing Gas Furnace Cancels: SM05-5 SM05-07 6-08 INDEX SAFETY CONSIDERATIONS PAGE Safety Considerations................................................................................. 1 Instructions.................................................................................................. 1 Example ......................................................................................................
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Let’s try our guide out using the EXAMPLE section below, and see how it works. Suppose that the problem is a defective low heat pressure switch (for example the contacts will not open). This is an internal problem and cannot simply be seen. We go to the START HERE section to Step 1. number in the GO TO column. Do whatever the ACTION says, then proceed to the step indicated in the GO TO column. If the ACTION is a question (a question will have a number in the YES or NO column), answer it YES or NO.
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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 at full speed until flame is no longer proved. The furnace will start up in either low- or high-heat. If the furnace starts up in low-heat, the control CPU determines the low-heat on-time (from 0 to 16 minutes) which is permitted before switching to high-heat. e.
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2. blower motor BLWM will continue operating at cooling airflow for an additional 90 seconds. Jumper Y/Y2 to DHUM to reduce the cooling off-delay to 5 seconds. (See Fig. 1.) TWO-STAGE THERMOSTAT AND TWO-STAGE HEATING Note: In this mode the low-heat only switch SW1-2 must be ON to select the low-heat only operation mode in response to closing the thermostat R to W1 circuit.
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furnace control on the DHUM input, the furnace control operates in Thermidistat mode. If the DHUM input is low for more than 48 hours, the furnace control reverts back to nonThermidistat mode. cooling airflow which is the true on-board CF selection as shown in Table 1. If the furnace control CPU switches from low-cooling to high-cooling, the furnace control CPU will energize the air conditioning relay ACR.
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signals disappear at the same time, the blower motor BLWM will remain on at low-heat airflow for the selected blower-OFF delay period. At the end of the blower-OFF delay, the blower motor BLWM will shut OFF unless G is still energized, in which case the blower motor BLWM will operate at continuous blower airflow.
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SERVICE/STATUS CODE INSTRUCTIONS If status code recall is needed disconnect the “R” thermostat lead, reset power, and put setup switch “SW1-1” in the ON position. To clear the status code history put setup switch “SW1-1” in the ON position and jumper thermostat terminals “R”, “W/W1”, and “Y/Y2” simultaneously until status code #11 is flashed. LED CODE CONTINUOUS OFF CONTINUOUS ON RAPID FLASHING - STATUS Check for 115 VAC at L1 and L2, and 24 VAC at SEC-1 and SEC-2. Control has 24 VAC power.
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33 34 41 42 43 45 LIMIT CIRCUIT FAULT – Indicates the limit, or flame rollout is open or the furnace is operating in high-heat only mode due to 2 successive low heat limit trips. Blower will run for 4 minutes or until open switch remakes whichever is longer. If open longer than 3 minutes, code changes to lockout #13. If open less than 3 minutes status code #33 continues to flash until blower shuts off. Flame rollout switch requires manual reset. Check for: Proper rear air baffle. Loose blower wheel.
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START HERE - If a problem exists, the service technician should always begin troubleshooting here. SPECIAL NOTE: ALL VOLTMETERS ARE NOT THE SAME - YOUR VOLTAGE READINGS WILL VARY. THIS APPLIES TO THE ENTIRE CONTENT OF THIS TROUBLESHOOTING MANUAL. THEY ARE NOT ABSOLUTE VALUES. CORRECT 115-VAC VOLTAGE, CURRENT, AND POWER MEASUREMENTS CANNOT BE TAKEN ON VARIABLE SPEED FURNACES UNLESS USING A TRUE RMS METER. STEP 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25.
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STEP 26. 27. 28. 29. 30. 31. ACTION Is 115-vac across the transformer leads? Replace the transformer. Is 24-vac across W/W1 and COM-24V on the variable speed furnace control? You will not be able to check for voltage across W/W1 and COM-24V if the furnace is connected to a User Interface at the ABCD connector. Go to step 29. You have a defective thermostat, or a break in wiring between thermostat and furnace. Fix problem.
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IMPROPER COOLING AIR FLOW - Generally, this indicates the Y/Y2 thermostat lead is not properly connected. If User Interface is connected to ABCD connector then the wrong size outdoor unit could be configured in the User Interface. STEP 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. ACTION Remove blower access panel and depress door switch. Use a piece of tape to hold switch closed. Set thermostat to call for cooling.
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Table 2 – Cooling Tonnage vs. Airflow (CFM) AIR CONDITIONING TONS (12,000 BTU/HR) 1-1/2 2 2-1/2 3 3-1/2 4 5 6 AIRFLOW (CFM) 525 700 875 1050 1225 1400 1750 2100 040, 060, & 3T080 MODEL X X X X X 5T-080 & 100 MODEL 120 MODEL X X X X X X X X X X X X X AIR CONDITIONING (A/C) OR CONTINUOUS-FAN (CF) AIRFLOW SELECTION CHART BASED ON 350 CFM/TON (SETUP SWITCH SW1-5 OFF) SETUP SWITCH SW3 POSITIONS MODEL SIZE 040, 060, 3T-080 DEF. 5252 700 875 10501 1225 1225 1225 5T-080, 100 DEF.
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STEP 12. 13. 14. 15. 16. ACTION Ensure the gas inlet pressure and burner orifice are correct. Then adjust the gas valve to the proper rate. If it cannot be adjusted to the proper rate, replace the gas valve. Is outdoor condensing unit operating during heating cycle? YES NO 16 14 GO TO 9 15 Check temperature rise and external static pressure with blower access panel in place. Temperature rise should be mid range or higher than midpoint of range stated on furnace rating plate.
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STEP 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. ACTION Disconnect the R thermostat lead. Do you have less than 19-vac across R and COM-24V on the variable speed furnace control? Replace transformer. The thermostat and/or thermostat wires are loading down the transformer. Replace the thermostat or repair thermostat wires. Does the hot surface ignitor HSI come on during the cycle? Disconnect the humidifier lead from HUM terminal on variable speed furnace control.
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STEP 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. ACTION Replace flame rollout switch FRS. Reset flame rollout switch FRS, turn power on, and observe furnace operation for (2) 15 minute cycles. Does the flame rollout switch FRS trip again? Does a different status code flash? You have inadequate combustion-air supply. This may be caused by: - Reversed vent and combustion-air pipes. - Poor burner, manifold, or orifice alignment. - Blocked heat exchanger.
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STEP 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. ACTION Go to page number indicated in the Index for the section covering the status code. Remove blower access panel and depress door switch. Use a piece of tape to hold switch closed. Jumper R and W/W1 thermostat terminals. Does status code 21 start flashing when the low heat pressure switch LPS makes? Replace the variable speed furnace control.
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STEP 15. 16. 17. 18. 19. 20. 21. 22. ACTION Replace variable speed furnace control. Is the low heat pressure switch LPS wired correctly? Replace the pressure switch assembly. Is the high heat pressure switch HPS wired correctly? Rewire high heat pressure switch HPS per wiring diagram. Replace the pressure switch assembly and replace the variable speed furnace control. Check the inducer PWM line.
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STEP 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. ACTION Disconnect jumper wire across R and W/W1 thermostat terminals and replace secondary voltage fuse. Disconnect BLUE wire to gas valve GV and jumper R and W/W1 thermostat terminals. Does status code 34 flash? If not, status code 24 should occur when BLUE wire is energized. Turn power off and disconnect PL1 from variable speed furnace control.
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Status Code 25 MODEL SELECTION OR SETUP ERROR – If status code 25 only flashes 4 times on power-up the variable speed furnace control is missing its model plug (PL4) and is defaulting to the model selection stored in memory. If status code 25 flashes continuously it could indicate any of the following: 1. Model plug (PL4) is missing and there is no valid model stored in permanent memory. This will happen if you forget to install the model plug (PL4) on a service replacement board. 2.
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- HIGH HEAT 1. PREPURGE - If the high heat pressure switch HPS does not make within 45 seconds after the low-heat pressure switch LPS made the variable speed begins flashing status code 31, shuts unit down, waits 2 minutes, stops flashing status code 31, and restarts heating cycle. If high heat pressure switch HPS opens before ignition, the variable speed starts flashing status code 31 and ramps inducer RPM up until the high heat pressure switch HPS remakes.
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STEP 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. ACTION Is inducer wheel okay? If possible, replace inducer wheel. Otherwise, replace inducer motor assembly. Is the inducer wheel properly mounted to the inducer motor shaft? Is there any frost build-up on the combustion-air inlet? Fix problem. You have excessive restriction in combustion-air or vent pipe. Also check for proper vent sizing for installation.
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STEP 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. ACTION You have an open wire or bad terminal on the YELLOW wire from the variable speed furnace control to the low heat pressure switch LPS. Repair or replace the main wire harness. Replace the variable speed furnace control. At start of cycle as inducer is ramping up, does low heat pressure switch LPS make then break? The problem is either a sag in vent pipe or a clogged drain trap or line. Also check for improperly plumbed drain tubing within furnace.
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Status Code 33 LIMIT CIRCUIT FAULT - This status code indicates the limit, or flame rollout switch is open or the furnace is operating in highheat only mode due to 2 successive low heat limit trips. Blower will run for 4 minutes or until the open switch remakes whichever is longer. If open longer than 3 minutes, code changes to lockout #13. If open less than 3 minutes status code #33 continues to flash until blower shuts off. Flame rollout switch requires manual reset. STEP ACTION YES NO GO TO 2 1.
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STEP 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67. 68. ACTION Remove tape from door switch, turn power off at main disconnect, and remove jumper across R and W/W1. Is the blower wheel firmly mounted on motor shaft? Does the model plug PL4 match the part number specified on the Model Plug Chart in the upper left hand corner of wiring schematic? Replace model plug. Turn power on and depress door switch.
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Status Code 34 IGNITION-PROVING FAULT - This status code indicates flame was not sensed during trial for ignition period. The control will repeat ignition sequence 3 more times before going to status code 14 - IGNITION LOCKOUT. This status code can also indicate flame signal was lost during steady-state operation. STEP ACTION YES NO GO TO 1.
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STEP 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. ACTION Clean flame sensor with fine sandpaper and make sure it is properly positioned then recheck current. Current is typically 4.0 to 6.0 microamps. Is current near typical value? Replace electrode. Will main burners ignite and stay on? Do you have burner pulsation’s? Check the following: - Make sure perforated disks are in combustion-air vent inlet. - Pressure tubing going to gas valve air pressure fitting for kinks.
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STEP 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. ACTION Replace the entire blower motor or blower control module attached to the blower motor. If you replace the blower control module go to step 36. Always inspect failed motor for water damage. If present, find source of water and fix it. Check A-coil and/or humidifier. Disconnect jumper wire across R and W/W1 thermostat terminals. Are all pins and wire leads intact on connectors between the variable speed furnace control and the blower motor.
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STEP 29. 30. 31. 32. 33. 34. 35. ACTION Does the voltage fluctuate as described in step 28? Reconnect PL3 to the variable speed furnace control and connect a DC voltmeter across terminals PL3-4 BLUE (+) and PL3-2 GREEN (-). Does the voltage fluctuate as described in step 28? Disconnect PL13 from the blower motor and connect a DC voltmeter across the BLUE (+) and GREEN (-) wires at connector PL13.
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STEP 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. ACTION Hook an AC voltmeter across PL2-4 and NEUTRAL-L2 on the variable speed furnace control. Is 115-vac across PL2-3 and NEUTRAL-L2? Replace the variable speed furnace control.
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STEP 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. ACTION Is inducer blower wheel okay? If possible, replace inducer wheel. Otherwise replace inducer motor assembly. Is there any frost build-up on combustion-air inlet? The problem is caused by reversed vent and combustion-air pipes or some other moist air entering combustion-air pipe. You have excessive restriction in combustion-air or vent pipe.
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STEP 14. 15. 16. 17. ACTION Is 24-vac across ORANGE wire on the low heat pressure switch LPS and COM-24V on variable speed furnace control? Is 24-vac across connector terminal PL1-4 and COM-24V on variable speed furnace control? Turn power off and disconnect jumper wire across R and W/W1 thermostat terminals. You have an open circuit between the low heat pressure switch LPS and the variable speed furnace control.
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APPENDIX A BOARD LAYOUT AND WIRING SCHEMATICS COMMUNICATION CONNECTOR MODEL PLUG CONNECTOR CONTINUOUS FAN (CF) AIRFLOW SETUP SWITCHES OUTDOOR AIR TEMP CONNECTOR SW4 SETUP SWITCHES SW1 SETUP SWITCHES AND BLOWER OFFDELAY AIR CONDITIONING (A/C) AIRFLOW SETUP SWITCHES HUMIDIFIER TERMINAL (24-VAC 0.5 AMP MAX.
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Fig. 2 – Schematic for 355MAV and 355AAV with ECM 2.
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Fig. 3 – Schematic for 355AAV with ECM 3.
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Fig. 4 – Schematic for 355BAV with ECM 2.
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APPENDIX B ECM BLOWER MOTOR DESCRIPTION & OPERATION The G.E. Electronically Commutated Motor (ECM) shown in figure 5 is different than previous generations of variable speed blower motors. This motor has all of the capabilities of previous ECM blower motors but it does not have to be pre-programmed at the factory.
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APPENDIX C PRESSURE CHECK DIAGRAM UNIT SIZE (BTUH) 40,000 60,000 80,000 100,000 120,000 UNIT SIZE (BTUH) 60,000 80,000 100,000 120,000 355MAV & 355AAV PRESSURE SWITCH MAKE/BREAK POINTS HIGH-HEAT PRESSURE SWITCH LOW-HEAT PRESSURE SWITCH Make Point Break Point Make Point Break Point 1.81 in.wc max 1.63 in. wc +/- 0.05 0.75 in. wc max 0.60 in. wc +/- 0.05 1.81 in.wc max 1.63 in. wc +/- 0.05 0.95 in. wc max 0.80 in. wc +/- 0.
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APPENDIX D STATIC PRESSURE READING LOCATION DIAGRAMS Figure 7 – Upflow Total Static Pressure Reading Locations Figure 8 – Downflow Total Static Pressure Reading Locations - 38 -
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Figure 9 – Horizontal Right Total Static Pressure Reading Locations Tools Needed: 1. 2. Pitot Tube Incline Manometer/Magnahelic Example 1: Return ESP after Filter Supply ESP before Coil -----------------------------------------------------Total ESP 0.20 in.w.c. 0.40 in.w.c. 0.60 in.w.c. Example 2: Return ESP before Filter 0.10 in.w.c. Filter Static Pressure Drop @ 2000 cfm 0.10 in.w.c. Supply ESP after Coil 0.20 in.w.c. Coil Static Pressure Drop Wet 0.20 in.w.c.
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APPENDIX E QUICK REFERENCE INFORMATION UNIT SIZE (BTUH) 40,000 60,000 80,000 100,000 120,000 355MAV & 355AAV PRESSURE SWITCH MAKE/BREAK POINTS HIGH-HEAT PRESSURE SWITCH LOW-HEAT PRESSURE SWITCH Make Point Break Point Make Point Break Point 1.81 in.wc max 1.63 in. wc +/- 0.05 0.75 in. wc max 0.60 in. wc +/- 0.05 1.81 in.wc max UNIT SIZE (BTUH) 60,000 80,000 100,000 120,000 1.63 in. wc +/- 0.05 0.95 in. wc max 0.80 in. wc +/- 0.
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APPENDIX F FURNACE STAGING ALGORITHM On initial thermostat call for heat after power-up, furnace staging algorithm will provide 16 minutes of low heat provided setup switch SW1-2 is off. If call for heat still exists after operating for 16 minutes in low heat, furnace switches to high heat until the thermostat is satisfied. During subsequent calls for heat: Low heat run time is calculated based on previous heating cycle. High heat run time is not calculated.
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A02281 - 42 -
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SERVICE TRAINING Packaged Service Training programs are an excellent way to increase your knowledge of the equipment discussed in this manual, including: • Unit Familiarization • Maintenance • Installation Overview • Operating Sequence A large selection of product, theory, and skills programs is available, using popular video-based formats and materials. All include video and/or slides, plus companion book.
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- 44 - Replaces: SM05-5 Form: SM05-07 6-08