Saunier Duval SD 30e Fault codes & diagnostics

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

Combi Natural Gas 30 kW 1994-2005 Discontinued

Replaced by: Thema F 30E

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 Saunier Duval SD 30e faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 4 documented codes

Tap any card for details

Lockout

Your boiler has stopped working because it cannot successfully start or maintain a flame, so it has safely shut itself down to prevent gas from building up.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Flame sensing lead
  • Printed Circuit Board (PCB)
Full explanation for Lockout
Low water pressure LED

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

High DIY-safe £80-150

What to check first

  1. Locate the two small taps (filling loop) usually found underneath the boiler
  2. Open the taps slowly to let fresh water into your heating system until the pressure gauge needle reaches the green zone (typically 1.0 to 1.5 bar)
  3. Close both taps firmly to prevent over-pressurisation

Parts commonly replaced

  • Pressure relief valve
  • Pressure switch
  • Expansion vessel
Full explanation for Low water pressure LED
Mains LEDs

Your boiler has lost all power and is completely unresponsive, likely due to an internal electrical protection component failing.

High Engineer only £150-350

Parts commonly replaced

  • Internal PCB fuse
  • Printed Circuit Board (PCB)
Full explanation for Mains LEDs
Red light F ON

Your boiler has detected a safety issue and has automatically switched itself off to prevent damage or dangerous operation.

High DIY-safe £120-250

What to check first

  1. Locate the reset button labeled 'G' on the front control panel.
  2. Press and hold the button firmly for a few seconds to see if the boiler restarts.
  3. If the boiler fires up, monitor it for a few hours to ensure the light does not return.

Parts commonly replaced

  • Overheat thermostat
  • Limit switch
  • Ignition lead
Full explanation for Red light F ON