Bryant 355CAV A Series Troubleshooting Manual
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Bryant 355CAV A Series Troubleshooting Manual

Bryant 355CAV A Series Troubleshooting Manual

Variable speed, step-modulating electronic condensing four-way multipoise gas furnace
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Safety Considerations................................................................................. 1
Instructions.................................................................................................. 1
Example ...................................................................................................... 2
General........................................................................................................ 2
Sequence of Operation ............................................................................... 2
(Adaptive Mode)................................................................................ 2
Cooling Mode .................................................................................... 5
Single-Speed Cooling ........................................................................ 5
Mode) ................................................................................................. 5
Two-Stage Thermostat and Two-Speed Cooling ............................. 5
Thermidistat Mode............................................................................. 6
Super-Dehumidify Mode................................................................... 6
Continuous-Blower Mode ................................................................. 6
Heat Pump Defrost............................................................................. 7
Component Test................................................................................. 7
Service/Status Code Instructions ............................................................... 8
Start Here .................................................................................................. 10
Rapid Flashing AMBER LED................................................................. 11
Improper Cooling Air Flow ..................................................................... 12
Status Code 11 - No Previous Code......................................................... 15
Status Code 12 - Blower On After Power Up ......................................... 15
Status Code 13 - Limit Circuit Lockout .................................................. 16
Status Code 14 - Ignition Lockout ........................................................... 17
Status Code 15 - Blower Motor Lockout................................................. 17
Status Code 21 - Gas Heating Lockout.................................................... 17
Status Code 22 - Abnormal Flame-Proving Signal................................. 18
Status Code 23 - Pressure Switch Did Not Open .................................... 18
Status Code 24 - Secondary Voltage Fuse Is Open................................. 19
Status Code 25 - Model Selection or Setup Error ................................... 21
Close or Reopen............................................................................... 22
Reopened.......................................................................................... 24
Status Code 33 - Limit Circuit Fault........................................................ 26
Status Code 34 - Ignition-Proving Fault .................................................. 28
Status Code 41 - Blower Motor Fault...................................................... 30
Status Code 42 - Inducer Motor Fault ..................................................... 32
Heat Pressure Switch Is Closed....................................................... 34
Status Code 45 - Control Circuitry Lockout........................................... 34
Cleanup and Start-Up Instructions........................................................... 35
APPENDIX A - Board Layout & Wiring Schematic ............................. 36
APPENDIX C - Pressure Check Diagram .............................................. 40
APPENDIX E - Quick Reference Information ....................................... 43
troubleshooting guide
Variable Speed, Step-Modulating
Electronic Condensing
Four-Way Multipoise Gas Furnace
APPENDIX F - Furnace Staging Algorithm...........................................44
PAGE
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.
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.
- 1 -
Cancels:
NEW

SAFETY CONSIDERATIONS

INSTRUCTIONS

355CAV
Series A
SM355CAV-01
10-08
.
!

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  • Page 1: Table Of Contents

    troubleshooting guide Variable Speed, Step-Modulating Electronic Condensing 355CAV Four-Way Multipoise Gas Furnace Series A Cancels: SM355CAV-01 10-08 INDEX APPENDIX F - Furnace Staging Algorithm...........44 PAGE Safety Considerations................. 1 SAFETY CONSIDERATIONS Instructions....................1 Example ...................... 2 Installing and servicing heating equipment can be hazardous due to General......................

  • Page 2: Index

    Once in a section, read the ACTION. An ACTION may have a Let’s try our guide out using the EXAMPLE section below, and see number in the GO TO column. Do whatever the ACTION says, then how it works. Suppose that the problem is a defective low heat proceed to the step indicated in the GO TO column.
  • Page 3 This furnace can operate as a step-modulating furnace with a If the furnace control CPU selects high-heat operation, the single-stage thermostat because the furnace control CPU high-heat gas valve solenoid GV-HI is energized when the includes a programmed adaptive sequence of controlled high-heat pressure switch HPS closes.

  • Page 4: Two-Stage Thermostat And Two-Stage Low/High Heating

    to medium-heat airflow five seconds after the furnace MPS are open, then de-energizes the HPSR relay to close the NC control CPU switches from low-heat to medium-heat. contact. Switching from Low- to High-Heat – If the furnace The start up and shut down functions and delays described above apply to the 2-stage low/high heating mode as well, except for control CPU switches from low-heat to high-heat, the furnace control CPU will de-energize the HPSR relay to...

  • Page 5: Cooling Mode

    COOLING MODE The furnace control CPU can start up the cooling unit in either low- or high-cooling. If starting up in low-cooling, The thermostat "calls for cooling". the furnace control CPU determines the low-cooling on- time (from 0 to 20 minutes) which is permitted before Single-Speed Cooling switching to high-cooling.

  • Page 6: Thermidistat Mode

    The electronic air cleaner terminal EAC-1 is energized to G circuit closes or the demand for dehumidification is with 115 vac whenever the blower motor BLWM is satisfied. High-cooling airflow is based on the A/C operating. selection shown in Table 1. When the thermostat is satisfied, the R to G-and-Y1 or Cooling Off-Delay –...

  • Page 7: Heat Pump Defrost

    desired and is stored in the memory to be automatically used following a power interruption. HEAT PUMP DEFROST When installed with a heat pump, the furnace control automatically changes the timing sequence to avoid long blower off times during demand defrost cycles. Whenever W/W1 is energized along with Y1 or Y/Y2, the furnace control CPU will transition to or bring on the blower motor BLWM at cooling airflow, low-heat airflow, or the midrange airflow, whichever is...

  • Page 8: Service/Status Code Instructions

    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.
  • Page 9 33 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 or medium heat limit trips. Blower will run at medium heat airflow for 4 minutes or until open switch remakes whichever is longer. If open longer than 3 minutes, code changes to lockout #13.

  • Page 10: Start Here

    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.

  • Page 11: Rapid Flashing Amber Led

    STEP ACTION GO TO Is 115-vac across the transformer leads? Replace the transformer. Is 24-vac across W/W1 and on the variable speed furnace control? You will not be able to check for voltage across W/W1 and C -24V if the furnace is connected to a User Interface at the ABCD connector.

  • Page 12: Improper Cooling Air Flow

    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 ACTION GO TO Remove blower access panel and depress door switch.

  • Page 13: Medium And/Or High Heat Temperature Rise Too Low

    Table 2 – Cooling Tonnage vs. Airflow (CFM) AIR CONDITIONING TONS AIRFLOW 060, & 3T-080 5T-080 & 100 120 MODEL (12,000 BTU/HR) (CFM) MODEL MODEL 1-1/2 2-1/2 1050 3-1/2 1225 1400 1750 2100 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...
  • Page 14 STEP ACTION GO TO Go to the page number indicated in Index for the CLEANUP AND STARTUP INDEX INSTRUCTIONS. Replace the gas valve GV. Is the high heat rate within 2% of that specified on the rating plate? Ensure the gas inlet pressure and burner orifice are correct. Then adjust the gas valve to the proper rate.

  • Page 15: Status Code 11 - No Previous Code

    Status Code 11 NO PREVIOUS CODE - Stored status codes are erased after 72 hours or can be cleared by jumpering R, W/W1, and Y/Y2 thermostat leads while setup switch SW1-1 is ON. Run system through a heating or cooling cycle to check system. This usually indicates one of the following: - The status history has been cleared and setup switch SW1-1 is in the ON position.

  • Page 16: Status Code 13 - Limit Circuit Lockout

    STEP ACTION GO TO Does the furnace abruptly shut down with no inducer post purge and then run blower motor BLWM for 90 seconds while AMBER LED status light flashes status code 12. Disconnect BROWN wire to gas valve GV. Does the furnace still abruptly shut down as described in Step 21.

  • Page 17: Status Code 14 - Ignition Lockout

    STEP ACTION GO TO Does furnace have the proper limit switch, limit shield, blower baffle (if used), and rear air baffle (if used)? If so, are the limit switch, limit shield, and heat exchangers properly aligned? Remove tape from door switch, turn power off at main disconnect, and remove jumper across R and W/W1.

  • Page 18: Status Code 22 - Abnormal Flame-Proving Signal

    STEP ACTION GO TO Cycle the furnace several times to check for intermittent operation. Does status code 21 ever flash? Go to page number indicated in Index for CLEANUP AND START-UP INSTRUCTIONS. If INDEX the problem persists on an intermittent basis, replace the variable speed furnace control. If problem still persists on an intermittent basis after replacing the variable speed furnace control, contact your distributor.

  • Page 19: Status Code 24 - Secondary Voltage Fuse Is Open

    Status Code 24 SECONDARY VOLTAGE FUSE IS OPEN - Indicates fuse is open and there is a short in low-voltage wiring. STEP ACTION GO TO Turn power off and remove the blower access panel. Is secondary voltage fuse blown? Check continuity to make sure. Replace variable speed furnace control.
  • Page 20 STEP ACTION GO TO Do you have continuity between the GRAY wire connected to both the medium and high heat pressure switches and chassis ground? You have a short circuit in the GRAY wire to the medium and high heat pressure switches. Does status code 24 begin flashing when the high heat pressure switch HPS is energized? Disconnect jumper wire across R, W/W1, and W2 thermostat terminals and replace secondary voltage fuse.

  • Page 21: Status Code 25 - Model Selection Or Setup Error

    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: Model plug (PL4) is missing and there is no valid model stored in permanent memory.

  • Page 22: Status Code 31 - Medium-Heat Switch Or Hpsr Relay Did Not Close Or Reopen

    Status Code 31 MEDIUM-HEAT PRESSURE SWITCH OR HPSR RELAY DID NOT CLOSE OR REOPENED - This status code can occur under the scenarios shown below. Keep in mind that whenever the variable speed furnace control shuts unit down, gas remains off or shuts off immediately, inducer continues running for 15 seconds, and if the blower is running, it remains running at low heat airflow or reduces to low heat airflow for the selected off-delay.
  • Page 23 pressure switch MPS remakes the variable speed furnace control continues heating cycle. If medium heat pressure switch MPS does not remake within 45 sec after opening, the variable speed furnace control starts flashing status code 31, shuts unit down, waits 2 minutes, stops flashing status code 31, and restarts heating cycle.

  • Page 24: Status Code 32 - Low-Heat Pressure Switch Did Not Close Or Reopened

    STEP ACTION GO TO Did the pressure gradually drop over time until the fault occurred? If the pressure remained constant and then the fault all of sudden occurred go to step 50. Check for a sag in vent pipe or partially clogged drain trap or line. Also check for improperly plumbed drainage tubing within furnace.
  • Page 25 STEP ACTION GO TO Fix problem. Does status code 32 flash once then flash status code 43? On propane installations the propane tank may be low otherwise you may have a loose connection between the low heat pressure switch LPS and the variable speed furnace control. This includes the ORANGE wire interconnecting the low heat pressure switch LPS to the variable speed furnace control.

  • Page 26: Status Code 33 - Limit Circuit Fault

    Status Code 33 LIMIT CIRCUIT FAULT - This status code indicates the limit, or flame rollout switch is open or the furnace is operating in high- heat only mode due to 2 successive low or medium heat limit trips. Blower will run for 4 minutes at medium heat airflow or until the open switch remakes whichever is longer.
  • Page 27 STEP ACTION GO TO 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.

  • Page 28: Status Code 34 - Ignition-Proving Fault

    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.
  • Page 29 STEP ACTION GO TO Clean flame sensor with fine steel wool 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.

  • Page 30: Status Code 41 - Blower Motor Fault

    Status Code 41 BLOWER MOTOR FAULT - This status code indicates the blower failed to reach 250 RPM or the blower failed to communicate to the variable speed furnace control within 30 seconds after being turned ON or within 10 seconds during steady-state operation.
  • Page 31 STEP ACTION GO TO Check the blower motor serial output signal. To do this disconnect PL3 from the furnace control and connect a DC voltmeter across terminals PL3-4 (+) and PL3-2 (-) on the variable speed furnace control. The voltage should be near 0-vdc but it will fluctuate briefly several times a second.

  • Page 32: Status Code 42 - Inducer Motor Fault

    STEP ACTION GO TO When blower control module is completely detached from blower motor, verify with standard ohmmeter that the resistance from each motor lead in motor plug to unpainted motor end plate is greater than 100k ohms. Then verify motor windings are not shorted or open by measuring resistance between each combination of pins in motor plug (there are three different combinations, pin 1-2, pin 2-3, and pin 1-3).
  • Page 33 STEP ACTION GO TO Reconnect collector box tube to pressure switch assembly. Disconnect jumper across R and W/W1 thermostat terminals. Check the RPM feedback line. To do this, connect a DC voltmeter across terminals PL11-2 BROWN (+) and PL11-1 ORANGE (-), then put setup switch SW1-6 for COMPONENT TEST in ON position.

  • Page 34: Status Code 43 - Low-Heat Pressure Switch Open While Medium-Heat Pressure Switch Is Closed

    Status Code 43 LOW-HEAT PRESSURE SWITCH OPEN WHILE MEDIUM-HEAT PRESSURE SWITCH IS CLOSED - This status code can occur as a result of the low heat pressure switch LPS not making during a call for heat. Keep in mind that whenever status code 43 occurs the variable speed furnace control shuts unit down, turns the inducer off, and gas remains off.

  • Page 35: Cleanup And Start-Up Instructions

    CLEANUP AND START-UP INSTRUCTIONS Start furnace using procedure outlined on Lighting Instructions attached to furnace. Observe operation of furnace through at least 1 complete heating cycle controlled from the room thermostat. Observe cycle for 20 minutes or until a status code is flashed. If status code flashes, refer to the Index.

  • Page 36: Appendix A - Board Layout & Wiring Schematic

    APPENDIX A BOARD LAYOUT AND WIRING SCHEMATICS COMMUNICATION CONTINUOUS FAN OUTDOOR SW4 SETUP CONNECTOR (CF) AIRFLOW AIR TEMP SWITCHES SETUP SWITCHES CONNECTOR MODEL PLUG CONNECTOR SW1 SETUP SWITCHES AND BLOWER OFF- DELAY AIR CONDITIONING (A/C) AIRFLOW SETUP SWITCHES HUMIDIFIER TERMINAL (24-VAC 0.5 AMP MAX.
  • Page 37 Fig. 2 – Wiring Schematic - 37 -...

  • Page 38: Appendix Becm Blower Motor Description & Operation

    APPENDIX B ECM BLOWER MOTOR DESCRIPTION & OPERATION The Regal-Beloit Electronically Commutated Motor (ECM) shown in figure 3 is the newest generation of variable speed blower motors. This motor has all of the capabilities of the previous ECM blower motor but has internal memory storage which provides operational information to the manufacturer when the motor is returned.
  • Page 39 Figure 3 – ECM Blower Motor - 39 -...

  • Page 40: Appendix Cpressure Check Diagram

    APPENDIX C PRESSURE CHECK DIAGRAM PRESSURE SWITCH MAKE/BREAK POINTS UNIT SIZE HIGH-HEAT PRESSURE SWITCH MED-HEAT PRESSURE SWITCH LOW-HEAT PRESSURE SWITCH (BTUH) Make Point Break Point Make Point Break Point Make Point Break Point 60,000 1.70 in. wc +/- 0.91 in. wc +/- 0.45 in.

  • Page 41: Appendix Dstatic Pressure Reading Location Diagrams

    APPENDIX D STATIC PRESSURE READING LOCATION DIAGRAMS Figure 5 – Upflow Total Static Pressure Reading Locations Figure 6 – Downflow Total Static Pressure Reading Locations - 41 -...
  • Page 42 Figure 7 – Horizontal Right Total Static Pressure Reading Locations Tools Needed: Pitot Tube Incline Manometer/Magnahelic Example 1: Return ESP after Filter 0.20 in.w.c. Supply ESP before Coil 0.40 in.w.c. ------------------------------------------------------ Total ESP 0.60 in.w.c. Example 2: Return ESP before Filter 0.10 in.w.c.

  • Page 43: Appendix Equick Reference Information

    APPENDIX E QUICK REFERENCE INFORMATION PRESSURE SWITCH MAKE/BREAK POINTS UNIT SIZE HIGH-HEAT PRESSURE SWITCH MED-HEAT PRESSURE SWITCH LOW-HEAT PRESSURE SWITCH (BTUH) Make Point Break Point Make Point Break Point Make Point Break Point 60,000 1.70 in. wc +/- 0.91 in. wc +/- 0.45 in.

  • Page 44: Appendix Ffurnace Staging Algorithm

    APPENDIX F FURNACE STAGING ALGORITHM On initial thermostat call for heat after power-up, furnace staging algorithm will provide 1 minute of medium heat followed by 15 minutes of low heat provided setup switches SW1-2 and SW4-2 are off. If call for heat still exists after operating for 1 minute in medium heat and 15 minutes in low heat, the furnace will switch to high heat until the thermostat is satisfied.
  • Page 45 Using recorded Low Heat (LH), Medium Heat (MH), and High Heat (HH) values calculate the Heat Load (HL) using: Thermostat is satisfied. HL=(140xLH)+(228xMH)+(350xHH) Unit will start the next cycle in The Low Heat, Medium Calculated Low Heat Medium Heat for 1 minute followed Heat, and High Heat run Is HL<2328 (LH) on time will be 15...
  • Page 46 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.
  • Page 47 - 47 -...
  • Page 48 - 48 - Replaces: NEW SM355CAV-01 10-08...

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