Navien NCB300-28K, Service Manual

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82 Troubleshooting
5.3 Troubleshooting guide by symptom
5.3.1 Noise
Error type Cause Check method
Vibration noise
Defective installation
Incorrect mounting to the wall or in an improper location.
●
Check for improper installation and reinstall the unit if necessary.
Fan vibration noise
Vibration caused due to defective blower.
●
Check the blower. If vibration is significant, replace the fan.
●
If intermittent noise occurs during operation, check the fan for debris.
●
If vibration noise occurs during operation of the product, and stops when
the case lid is removed, check the fan.
Regular noise
Defective flow sensor Rotating noise due to debris caught in the flow sensor.
Malfunction of the 3-way
valve
Noise due to repeated operation of the 3-way valve due to a defective PCB.
Noise at ignition
Gas and air differential
pressure error
(Pop, Beep, Explosive
ignition)
1. Offset pressure adjustment error.
●
Adjust offset pressure with the pressure adjusting screw on the main
gas valve.
●
Use the Front Panel to set the unit at “MIN.1”.
●
If noise occurs at standard value, adjust setting above / below the
standard.
2. Gas supply error due to defective air pressure sensor.
3. If the same error is repeated, it is due to a defective PCB.
Noise during combustion
Boiling noise
●
How to check boiling:
●
The heat exchanger is clogged partially due to scale deposits. Flush the
main heat exchanger to remove scale.
●
Replace the heat exchanger if the error occurs from the start of the
installation.
Whirring
Exhaust gas that is recirculated into the boiler through the air inlet could
produce abnormal combustion noises.
●
Check the distance between intake and exhaust (at least 12” (300 mm)).
●
Check the distance between flues if two or more units are installed (at least
12” (300 mm)).
●
Check if there are any obstructions near the flue.
Low gas pressure
(whirring)
1. Noise occurs due to low gas pressure.
●
Check the gas supply pressure (dynamic pressure).
2. Low gas supply due to offset pressure error.
●
Use the Front Panel to set the unit at “MIN.1”.
Noise due to defective air pressure sensor.
●
Replace the air pressure sensor.
Noise during combustion
●
Noise due to damaged air pressure hose.
●
Noise may be intermittent depending on the size of the damage.