Navien NCB-34LDWE Fault codes & diagnostics

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

Combi Natural GasLPG 35 kW 2014-present
GC Number 47-709-03
Download the Navien NCB-34LDWE manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

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Severity at a glance

Each cell = one fault code. Hover to identify.
1 Emergency 5 High
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
47-709-03 NCB-34LDWE 2014–present
Just want the most common Navien NCB-34LDWE faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 6 documented codes

Tap any card for details

003

Your boiler has failed to light the flame properly and has stopped attempting to heat your home or water for safety reasons.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Flame sensor

Related codes

Full explanation for 003
016

Your boiler has detected an issue related to the flow of water inside the unit, which has caused it to stop working to protect itself from potential overheating.

High Engineer only £150-300

Parts commonly replaced

  • Flow sensor
  • Circulation pump
  • Diverter valve
Full explanation for 016
060

Your boiler has detected an issue with the air supply or exhaust system, meaning it cannot operate safely and has shut down to prevent damage.

High Engineer only £150-350

Parts commonly replaced

  • Fan assembly
  • Air pressure switch
  • Flue system components
Full explanation for 060
110

Your boiler has detected that it is not effectively removing waste gases produced during the heating process, causing it to shut down for safety.

Emergency Engineer only £150-350

Parts commonly replaced

  • Flue system components
  • Air pressure switch
  • Fan assembly

Related codes

Full explanation for 110
205

Your boiler has detected an issue with the air flowing through the flue system, causing it to shut down for safety.

High Engineer only £150-300

Parts commonly replaced

  • Fan assembly
  • Air pressure switch
  • Flue seals
Full explanation for 205
E02

Your boiler has stopped working because the water pressure inside the system has dropped too low to operate safely.

High DIY-safe £80-150

What to check first

  1. Locate the filling loop (usually two silver flexible hoses) underneath the boiler.
  2. Open the valves slowly to allow mains cold water into the system.
  3. Watch the pressure gauge on the front of the boiler until the needle reaches the green zone (typically 1.0 to 1.5 bar).
  4. Close both valves tightly to stop the flow of water.

Parts commonly replaced

  • Filling loop
  • Pressure relief valve
  • Expansion vessel

Related codes

Full explanation for E02
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