Navien NCB300-28K, Service Manual

Page: 74 / 108

Troubleshooting 73
Testing method
Fault Possible Causes Testing method
Fan action error
No fan operation
1. Check the voltage at the fan.
●
Black + Yellow, DC 340 V
2. Replace the PCB if the voltage is not present. When replacing a PCB, turn
off the boiler and wait for at least 10 sec before proceeding.
3. If the error condition continues after checking these items, replace the fan
motor.
Check the fan motor’s wiring connection
Fan motor speed error Rotation fault
1. If fan speed is very low and the power supply is normal, follow the
instructions below to replace the fan.
1) Unplug the boiler’s power cable and wait 10 sec for all remaining SMPS
voltage to completely discharge.
2) Disconnect the fan cable and then re-connect it.
3) Reconnect the power cable and turn on the boiler.
4) Fan Auto Adjusting verifies error conditions for error code E109. If an
E109 error occurs, enter Fan test mode and verify fan speed and the
APS input voltage. (Eg. The display will show H.320 indicating 3,200
rpm)
5) If fan speed is low or there is a sensor circuit error, replace the fan.
This condition indicates an imminently hazardous situation which, if
not avoided, may result in minor or moderate injury.
2. If the error condition continues after checking these items, replace the
PCB.