Navien NCB-24LSWE, Service Manual

Page: 121 / 144

NCB Service Manual 119 Version 1.0
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 (refer to page 21).

Adjust offset pressure with the pressure adjusting screw on the main gas
valve.

Use the Front Panel to set the unit at "MIN.1" (refer to page 55).

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" (300mm)).

Check the distance between flues if two or more units are installed (at least 12"
(300mm)).

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 (refer to page 21).

Use the Front Panel to set the unit at "MIN.1" (refer to page 55).
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.