Saunier Duval SD 30e Fault codes & diagnostics

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

Combi Natural Gas 30 kW 1999-2003 Discontinued
GC Numbers 47-920-1647-920-50

Replaced by: Thema F 30E

Download the Saunier Duval SD 30e 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 →

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
47-920-16 Saunier Duval SD30e A 1999–2003
47-920-50 SD Themaplus Condens F 30 E 2005–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 2 documented codes

Tap any card for details

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
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