Navien NHB-055, Service Manual

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74 NHB Service Manual Version 1.0
4.9.10 Primary Heat Exchanger
Part Check Point
Function
1. Main part for heat transfer from the burner.
2. There are multiple paths of water pipes on the heat exchanger surface as well as inside the
combustion chamber which minimizes the heat loss.
Failure Event
1. Water and/or exhaust gas leakage through a crack.
2. Improper heat transfer can cause the water in the heat exchanger to boil due to possible scale
formation.
Effects
1. Exhaust gas leakage.
2. Excessive heating of the water that produces boiling noises.
Error Code E016, E030, E047
Diagnostic
1. Visual inspection: Check if there is a crack on the surface of heat exchanger.
2. Sound inspection: Check if boiling occurs inside the unit.
Color / Number of wires N / A