Baxi Luna 3 Comfort Fault codes & diagnostics

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

Combi Natural GasLPG 24-31 kW 2005-2015 Discontinued

Replaced by: Duo-tec

Download the Baxi Luna 3 Comfort manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

The fault code is already on your display

Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →

Just want the most common Baxi Luna 3 Comfort faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 3 documented codes

Tap any card for details

10E

Your boiler doesn't have enough water inside it to operate safely, which is why it has stopped working.

High DIY-safe £0-120 Shared across the range

What to check first

  1. Locate the filling loop (usually a silver flexible hose) under the boiler.
  2. Slowly open the one or two taps/valves until you hear water entering the system.
  3. Watch the pressure gauge until it reaches between 1.0 and 1.5 bar, then close the valves tightly.

Parts commonly replaced

  • Filling loop
  • Expansion vessel
  • Pressure sensor
Full explanation for 10E
25E

Your boiler has reached its maximum safe temperature and has shut down as a safety precaution to prevent overheating.

High DIY-safe £100-£350 Shared across the range

What to check first

  1. Check if any radiator valves are turned off and open them fully to allow water flow.
  2. Ensure your system pressure is between 1 and 1.5 bar on the pressure gauge.
  3. Try resetting the boiler via the control panel.

Parts commonly replaced

  • Circulation pump
  • Heat exchanger
  • Temperature sensor (NTC thermistor)

Related codes

Full explanation for 25E
E110

Your boiler has switched itself off because it has detected that it is getting dangerously hot inside.

High DIY-safe £100-280 Shared across the range

What to check first

  1. Turn the boiler off and allow it to cool down for 30 minutes
  2. Ensure all radiator valves are fully open to allow water to flow
  3. Check that the system pressure is between 1 and 1.5 bar
  4. Reset the boiler using the control knob or button

Parts commonly replaced

  • Overheat Thermostat
  • Circulation Pump
  • Temperature Sensor (NTC)
Full explanation for E110