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

Glow-worm print F.28 as "Fault: Ignition unsuccessful when starting up", and the operating instructions for the Energy7, Ultimate3 and Betacom4 all explain how you got there: "after three unsuccessful ignition attempts, the product switches to fault mode". The boiler has already tried three times before you see the code. The installation manuals then give the longest cause list in the whole table — a gas meter fault or gas pressure switch that has tripped, air in the gas, gas pressure too low, a thermal cut-out, the wrong gas injector, a wrong or faulty gas valve, a plug not seated on the board, a break in the harness, the ignition transformer, cable, plug or electrode, an interrupted ionisation signal, poor earthing, or the electronics — and the Energy7 and Compact editions add one more that is yours to check: a blocked condensate siphon or discharge pipe.

The Compact user guide is the most helpful Glow-worm document on this code. It tells the householder to check the gas stopcock is open, to "check at the gas meter that gas is still being supplied", adding that "if you have not topped up your payment recently, the gas supply could be cut off by the meter", and only then to call a competent person.

Glow-worm's homeowner fault-code page gives the same three checks — other gas appliances, prepayment credit, ice in an outdoor condensate pipe — and adds the electrode, the PCB and the flue to the causes. The Ultracom2 and Betacom2 tables also carry F28, with no gas or insufficient gas flow, a mis-set gas valve and a defective electrode or igniter as the causes, and the Betacom 24a installation manual adds a warning worth repeating: do not use the reset button to purge the gas line, and never press it more than three times.

1. 1

   Check the gas. Will the hob light? Is a prepayment meter in credit, including emergency credit that may have run out? Is the gas isolator under the boiler fully open? Glow-worm's Compact guide puts these first for a reason.

2. 2

   Follow the condensate pipe — the plastic pipe leaving the bottom of the boiler — to where it discharges. If it runs outside and the weather has been freezing, feel for a solid, cold section and thaw it with warm water, not boiling.

3. 3

   Reset as your guide says: press the reset button for one second on an Energy7, press the button on an Ultimate3 or Betacom4, hold the on/off button for more than three seconds on a Compact. The boiler makes a fresh ignition attempt.

   Glow-worm allow three resets. Each one runs the full ignition sequence with the gas valve open, and the Betacom 24a manual says outright never to press reset more than three times. If it is still F.28 after three, stop.
4. 4

   Call a Gas Safe registered engineer if the third reset fails, and tell them whether the gas and condensate checks were clear — that saves the first twenty minutes of the visit.