Bryant 355MAV Troubleshooting Guide

- 1 - troubleshooting guide 355MAV Variable Speed, Two-Stage Series H & I Electronic Condensing 355AAV Gas Furnace 355BAV Can

- 10 - STEP ACTION YES NO GO TO 26. Is 115-vac across the transformer leads? 27 25 27. Replace the transformer. 18 28. Is 24-vac across

- 11 - IMPROPER COOLING AIR FLOW - Generally, this indicates the Y/Y2 thermostat lead is not properly connected. If User Interface is connected to

- 12 - Table 2 – Cooling Tonnage vs. Airflow (CFM) AIR CONDITIONING TONS (12,000 BTU/HR) AIRFLOW (CFM) 040, 060, & 3T-080 MODEL 5T-080 & 100

- 13 - STEP ACTION YES NO GO TO 12. Ensure the gas inlet pressure and burner orifice are correct. Then adjust the gas valve to the proper rate.

- 14 - STEP ACTION YES NO GO TO 10. Disconnect the R thermostat lead. 11 11. Do you have less than 19-vac across R and COM-24V on the variab

- 15 - STEP ACTION YES NO GO TO 19. Replace flame rollout switch FRS. 10 20. Reset flame rollout switch FRS, turn power on, and observe furn

- 16 - STEP ACTION YES NO GO TO 7. Go to page number indicated in the Index for the section covering the status code. INDEX 8. Remove blower

- 17 - STEP ACTION YES NO GO TO 15. Replace variable speed furnace control. 7 16. Is the low heat pressure switch LPS wired correctly? 17

- 18 - STEP ACTION YES NO GO TO 27. Disconnect jumper wire across R and W/W1 thermostat terminals and replace secondary voltage fuse. 28 28. Di

- 19 - 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 miss

- 2 - 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 (

- 20 - - 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

- 21 - STEP ACTION YES NO GO TO 28. Is inducer wheel okay? 30 29 29. If possible, replace inducer wheel. Otherwise, replace inducer motor as

- 22 - STEP ACTION YES NO GO TO 11. You have an open wire or bad terminal on the YELLOW wire from the variable speed furnace control to the low he

- 23 - Status Code 33 LIMIT CIRCUIT FAULT - This status code indicates the limit, or flame rollout switch is open or the furnace is operating in hi

- 24 - STEP ACTION YES NO GO TO 40. Remove tape from door switch, turn power off at main disconnect, and remove jumper across R and W/W1. 41 41.

- 25 - Status Code 34 IGNITION-PROVING FAULT - This status code indicates flame was not sensed during trial for ignition period. The control will

- 26 - STEP ACTION YES NO GO TO 32. Clean flame sensor with fine sandpaper and make sure it is properly positioned then recheck current. Current

- 27 - STEP ACTION YES NO GO TO 15. Replace the entire blower motor or blower control module attached to the blower motor. If you replace the blo

- 28 - STEP ACTION YES NO GO TO 29. Does the voltage fluctuate as described in step 28? 30 20 30. Reconnect PL3 to the variable speed furnace

- 29 - STEP ACTION YES NO GO TO 10. Hook an AC voltmeter across PL2-4 and NEUTRAL-L2 on the variable speed furnace control. Is 115-vac across PL2

- 3 - 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

- 30 - STEP ACTION YES NO GO TO 47. Is inducer blower wheel okay? 49 48 48. If possible, replace inducer wheel. Otherwise replace inducer mo

- 31 - STEP ACTION YES NO GO TO 14. Is 24-vac across ORANGE wire on the low heat pressure switch LPS and COM-24V on variable speed furnace control

- 32 - APPENDIX A BOARD LAYOUT AND WIRING SCHEMATICS Fig. 1 – Variable Speed Furnace Control 24-V THERMOSTAT TERMINALS PL2 – HOT SURFACE IGNIT

- 33 - Fig. 2 – Schematic for 355MAV and 355AAV with ECM 2.5 Blower Motor

- 34 - Fig. 3 – Schematic for 355AAV with ECM 3.0 Blower Motor

- 35 - Fig. 4 – Schematic for 355BAV with ECM 2.5 Blower Motor

- 36 - APPENDIX B ECM BLOWER MOTOR DESCRIPTION & OPERATION The G.E. Electronically Commutated Motor (ECM) shown in figure 5 is different th

- 37 - APPENDIX C PRESSURE CHECK DIAGRAM 355MAV & 355AAV PRESSURE SWITCH MAKE/BREAK POINTS HIGH-HEAT PRESSURE SWITCH LOW-HEAT PRESSURE SWI

- 38 - APPENDIX D STATIC PRESSURE READING LOCATION DIAGRAMS Figure 7 – Upflow Total Static Pressure Reading Locations Figure 8 – Downflow

- 39 - Tools Needed: 1. Pitot Tube 2. Incline Manometer/Magnahelic Example 1: Return ESP after Filter 0.20 in.w.c. Supply ESP

- 4 - 2. 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 operat

- 40 - APPENDIX E QUICK REFERENCE INFORMATION 355MAV & 355AAV PRESSURE SWITCH MAKE/BREAK POINTS HIGH-HEAT PRESSURE SWITCH LOW-HEAT PRESSUR

- 41 - APPENDIX F FURNACE STAGING ALGORITHM On initial thermostat call for heat after power-up, furnace staging algorithm will provide 16 minut

- 42 - A02281

- 43 - SERVICE TRAINING Packaged Service Training programs are an excellent way to increase your knowledge of the equipment discussed in this

- 44 - Replaces: SM05-5 Form: SM05-07 6-08

- 5 - 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-cool

- 6 - blower motor BLWM will remain ON until the main burners ignite then shut OFF and remain OFF for the blower-ON delay (60 seconds in low-heat, an

- 7 - SERVICE/STATUS CODE INSTRUCTIONS If status code recall is needed disconnect the “R” thermostat lead, reset power, and put setup switch “SW1-1”

- 8 - 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

- 9 - START HERE - If a problem exists, the service technician should always begin troubleshooting here. SPECIAL NOTE: ALL VOLTMETERS ARE NOT THE SAM