Bryant 577D----A C. Indoor Fan Motor Troubleshooting, D. Furnace Control Troubleshooting

emergency heating or cooling operation using a common thermostat and the terminal strip connections on the two control boards (See Non-Communicating Emergency Cooling/Heating Mode) and will display Status Code 16, System Communication Fault, on amber STATUS LED. No further troubleshooting information will be available at UI until communications are re-established.

If either COMM LED does not light within proper time period and status codes are not displayed;

1.Check system transformer high- and low-voltage to be sure the system is powered.

2.Check ABCD connection on both boards.

3.Check fuse on furnace board to be sure it is not blown. If fuse is open, check system wiring before replacing it to be sure a short does not cause a failure of replacement fuse.

If COMM LED does not light within proper time period and status code is displayed:

1.Check system wiring to be sure UI is powered and connections are made A to A, B to B, etc. and wiring is not shorted. Miswiring or shorting of the ABCD communications wiring will not allow successful communications.

NOTE: Shorting or miswiring low-voltage system wiring will not cause damage to unit control or UI but may cause low voltage fuse to open.

C. Indoor Fan Motor Troubleshooting

The indoor fan is driven by an ECM motor consisting of two parts: the control module and the motor winding section. Do not assume motor or module is defective if it will not start. Use the designed-in LED information aids and follow troubleshooting steps described below before replacing motor control module or entire motor. Motor control module is available as a replacement part.

VERIFY MOTOR WINDING SECTION

!WARNING

ELECTRICAL SHOCK HAZARD

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

After disconnecting power from the ECM motor, wait at least 5 minutes before removing the control section. Internal capacitors require time to discharge.

Before proceeding to replace a motor control module:

1.Check motor winding section to be sure it is functional.

2.Remove motor control module section and unplug winding plug. Motor shaft should turn freely, resistance between any two motor leads should be similar and resistance between any motor lead and unpainted motor end should exceed 100,000 ohms.

3.Failing any of these tests, entire ECM motor must be replaced.

4.Passing all of the tests, motor control module alone can be replaced.

MOTOR TURNS SLOWLY

1.Low static pressure loading of blower while access panel is removed will cause blower to run slowly. Particularly at low airflow requests. This is normal, do not assume a fault exists.

2.Recheck airflow and system static pressure using UI service screens with access panel in place.

NOTE: Blower motor faults will not cause a lockout of blower operation. The fan coil control will attempt to run the blower motor as long as UI maintains a demand for airflow. The control will not

operate electric heaters while a fault condition exists. The control communicates with the motor at least once every five seconds, even when the motor is idle. If, during operation, the control does not communicate with the motor for more than 25 seconds, the motor will shut itself down and wait for communications to be reestablished.

D. Furnace Control Troubleshooting

Furnace control faults indicated by flashing codes on the amber system STATUS LED can be resolved using troubleshooting information provided below. Codes are listed in order of their priority, highest to lowest. Though multiple faults can exist at any time, only the highest priority code will be displayed on STATUS LED. Clearing the indicated fault when multiple faults exist will cause the next highest priority Status Code to be flashed. All existing faults, as well as a fault history, can be viewed at UI.

STATUS CODE CONTINUOUS OFF

Check for 230 VAC at L1 and L2, and 24 VAC at SEC-1 and SEC-2.

STATUS CODE CONTINUOUS ON Control has 24 VAC power.

STATUS CODE 11 - NO PREVIOUS CODE

Stored status codes are erased automatically after 72 hours.

STATUS CODE 12 - BLOWER ON AFTER POWER UP

(230 VAC or 24 VAC) Blower runs for 90 seconds if unit is powered up during a call for heat (R-W/W1 closed) or (R-W/W1 opens) during blower on-delay period.

STATUS CODE 13 - LIMIT CIRCUIT LOCKOUT

Lockout occurs if a limit or flame rollout switch is open longer than 3 minutes or 10 successive limit trips occurred during high heat. Control will auto reset after three hours. Refer to status code 33.

STATUS CODE 14 - IGNITION LOCKOUT

Control will auto reset after three hours. Refer to status code 34.

STATUS CODE 15 - BLOWER MOTOR LOCKOUT

Indicates the blower failed to reach 250 RPM or the blower failed to communicate within 30 seconds after being turned ON in two successive heating cycles. Control will auto reset after 3 hours. Refer to status code 41.

A06026

Fig. 15 - Detail of Furnace Board

577D-- -- A

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