Glow-worm [F.28] fault codewhat it means and how to fix it

Glow-worm sits within the Vaillant Group, and the practical consequence is that Glow-worm F codes on the Energy, Ultimate and Betacom ranges map closely onto Vaillant ecoTEC numbering. F.28 is unsuccessful ignition at start-up: the appliance ran its sequence and never got confirmation of a flame. It is the single most common Glow-worm lockout. What makes it frustrating is that the code covers several genuinely different problems with wildly different costs, and it does not tell you which. Two of them are householder-checkable in ten minutes — whether gas is reaching the property at all, and whether the condensate drain has frozen outside. The other two, a worn ignition electrode and a gas valve fault, need an engineer. Because Glow-worm appliances share the Vaillant ignition chain, an engineer familiar with ecoTEC diagnosis will recognise the fault pattern immediately, which is worth mentioning when you book.

1. 1

   Light a gas hob ring. If it will not light either, the supply is the problem and the boiler is behaving correctly.

2. 2

   Check any prepayment meter for credit, including emergency credit that may have run out overnight.

3. 3

   Outside, follow the plastic condensate pipe down from the appliance and feel for a rigid, ice-cold section. Bends and the open end freeze first.

4. 4

   Pour hand-hot water slowly along any frozen part until you hear it running clear at the end.

   Never boiling water, never a heat gun, never a naked flame. Cracking a cold plastic pipe in January creates a considerably worse problem.
5. 5

   Hold the reset button for around three seconds. If it fires and holds, the condensate was the cause — get the pipe lagged before next winter.