Troubleshooting Guide By Symptom; Noise - Navien NCB-700-2S+/42K Service Manual

5.3 Troubleshooting guide by symptom

5.3.1 Noise

Error type
Vibration noise
Regular noise
Noise at ignition
Noise during combustion
102 Troubleshooting
Cause
Incorrect mounting to the wall or in an improper location.
Defective installation
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Vibration caused due to defective blower.
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Fan vibration noise
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Defective flow sensor Rotating noise due to debris caught in the flow sensor.
Malfunction of the 3-way
Noise due to repeated operation of the 3-way valve due to a defective PCB.
valve
1. Offset pressure adjustment error.
Gas and air differential
pressure error
(Pop, Beep, Explosive
ignition)
2. Gas supply error due to defective air pressure sensor.
3. If the same error is repeated, it is due to a defective PCB.
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Boiling noise
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Exhaust gas that is recirculated into the boiler through the air inlet could
produce abnormal combustion noises.
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Whirring
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1. Noise occurs due to low gas pressure.
2. Low gas supply due to offset pressure error.
Low gas pressure
(whirring)
Noise due to defective air pressure sensor.
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Noise during combustion
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Check for improper installation and reinstall the unit if necessary.
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.
Adjust offset pressure with the pressure adjusting screw on the main
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gas valve.
Use the Front Panel to set the unit at "MIN.1".
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If noise occurs at standard value, adjust setting above / below the
●
standard.
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.
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.
Check the gas supply pressure (dynamic pressure).
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Use the Front Panel to set the unit at "MIN.1".
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Replace the air pressure sensor.
Noise due to damaged air pressure hose.
Noise may be intermittent depending on the size of the damage.
Check method