Glow-worm Ultimate Fault Codes
The Glow-worm Ultimate sits at the top of the range — the same Vaillant-group platform as the Energy, specified up with premium components (including a grade of internals closer to the Vaillant parent's own) and the brand's longest warranties. Its fault language is the shared F-code scheme: F22 low pressure, F28/F29 ignition and flame loss, F75 pump/pressure sensor, and the platform's sensor and electronics codes beyond. Diagnostically the Ultimate is an Energy with better parts and longer cover — which mostly means the warranty should be your first thought when a code persists. The meanings below are identical across the family, and each links through to the full cause-and-fix page.
Where Ultimate fault codes appear
The Ultimate carries the family digital display: status in normal running, F-prefixed codes on faults. Note the exact number; if the boiler is in warranty, note it before any engineer opens the case, since the code is what the support line asks for first.
Resetting a Glow-worm Ultimate
Press the reset button briefly and the boiler retries; F22 wants a top-up to 1–1.5 bar first. On an in-warranty Ultimate a returning code should go to Glow-worm's support line rather than a paid repair — and the annual service that keeps warranty valid is the same one that keeps this page academic.
Common Ultimate problems
The Ultimate's real-world code list matches the platform — F22, F28/F29, F75 — at somewhat lower frequency thanks to the component spec. Winter condensate freezes respect no price tier, so the warm-water thaw on the condensate pipe remains the first move for a cold-snap F28 here as anywhere.
Most common Ultimate fault codes
- F22 The F22 fault code on a Glow-Worm boiler signals that the water pressure inside your… Read more →
- F28 The F28 code means your Glow-Worm boiler attempted to light the burner, failed to detect… Read more →
- F29 The F29 code on a Glow-Worm boiler means the burner managed to light but the flame then… Read more →
- F75 The F75 code appears when the boiler's pressure sensor fails to detect any change in… Read more →
- F27 The F27 code indicates that your Glow-Worm boiler has attempted to ignite but its flame… Read more →