Navien NHB-055, Service Manual

Page: 103 / 147

NHB Service Manual 103 Version 1.0
5.2.10 109Error
Error occurrence conditions and check items
Error Description
E109
Fan motor RPM error
The system checks the RPM signal after the fan starts to run, and displays the error message
109E (cleared manually) in the following cases:
1. If the RPM remains low or close to 0, the system determines RPM error, and the boiler
switches into Lock-Out (gas valve and ignition transformer locked). (However, the air
pressure sensor should be normal.)
2. If the RPM signal of low or close to 0, is detected for 3 seconds during combustion, the
system stops combustion, and the boiler switches into Lock-Out. (However, the air volume
sensor should be normal.)
Check items
1. Check if the fan motor works normally using the component test mode (refer to page 57).
2. Check the power supply to the fan (Black + Red, approx. DC 127~184 V)
3. If RPM is significantly low while the fan works and the power supply is normal, replace the
fan motor.
4. If the fan connector is wet due to any reason including leakage, take corrective action
by powering the unit OFF, then drying the components completely before continuing
operation.
5. Check for loose connection of white connector that attaches the fan motor to the PCB.
Does the fan motor have
nominal operation voltage?
Is there any voltage from
the fan motor?
Check fan assembly
Check the PCB
Check power and connector
Check the voltage between #4 and #7 CN 8:
127-184V DC (check page 62 for Wiring Diagram)
Check the voltage between #3 and #4 CN 8:
0-7.5V DC
No
No
Yes
Yes