Navien NCB300-28K, Service Manual

Page: 47 / 108

46 System Details
4.7.10 Primary Heat Exchanger
Item Description
Function
1. Main component used in the boiler for heat transfer.
2. Multiple pipes on surface of the heat exchanger and inside the combustion chamber are used to
minimise heat loss.
Fault
1. Water and / or exhaust gas leaks.
2. Scale deposits in the heat exchanger can cause water in the boiler to bubble.
Symptoms
1. Exhaust gas leaks.
2. Overheating of water causes bubbling noises.
Error codes E016, E030, E047
Diagnostics
1. Visual inspection: Check for surface cracks on the heat exchanger.
2. Audible inspection: Listen for bubbling noises from inside the boiler.