Navien NCB-28LHWE Fault codes & diagnostics

1 fault code with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.

Gas 2014-present
GC Number 41-709-03
Download the Navien NCB-28LHWE manualThe official installation and service manual (PDF), the document these fault codes were read from. PDF

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Versions & GC numbers

Which version do you have?

The GC number on your boiler's data badge identifies the exact appliance and production years, as recorded in the UK Product Characteristics Database.

GC number Appliance (register name) Produced
41-709-03 NCB-28LHWE 2014–present

Appliance names and production years are taken from the UK Product Characteristics Database (the SAP/SEDBUK register). Where a GC number is also printed in this model's own manufacturer manual, both sources were checked to agree.

Fault codes

All 1 documented codes

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E02

Your boiler has temporarily stopped working because the water pressure inside the system has dropped too low.

High DIY-safe

What to check first

  1. Locate the filling loop or key underneath your boiler.
  2. Open the valves slowly to let mains water into the heating system.
  3. Watch the pressure gauge until the needle sits between 1.0 and 1.5 bar, then firmly close the valves.

Parts commonly replaced

  • Pressure sensor
  • Filling loop valve

Related codes

Full explanation for E02
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