Makes we repair
What does F28 mean?
F28 means the boiler tried to light its burner and found no flame. The boiler never lit at all. A Vaillant or Glow-worm boiler makes a few tries to light. When none of them works, it stops, locks out for safety and shows F28.
The cause of an F28 can be as simple as the gas being off, or a condensate pipe frozen in a frost. It can also be one of the parts that light the burner or watch for its flame. The gas and the condensate pipe are safe to check yourself, and the parts are an engineer's.
Which boilers show F28?
F28 is a code of Vaillant and Glow-worm, two makes of the same group, and it means the same on both. The way it shows depends on the boiler's age.
Vaillant F28
Vaillant's ecoTEC plus models before 2023 show F.28, and so do the ecoTEC pro, the ecoTEC exclusive, the ecoFIT and the open-vent ecoTEC plus. The current ecoTEC plus, from 2023, shows F.028 with a line of text. It shows F.281 if the flame went out while it was settling after lighting.
Vaillant's older user guides say the boiler locks out after three tries to light, and the current one says five. Vaillant boiler repair, and every other Vaillant code.
Glow-worm F28
Glow-worm's Energy7, Ultimate3 and Betacom4 show F.28. The Betacom2, Betacom a and Ultracom2 show F28, with no dot, meaning the same. The older Flexicom, the first Ultracom, the cxi and the CI show the same fault as F1. On a current Glow-worm, F.1 is a different fault, a sensor, so read the model before the code. Glow-worm boiler repair, and every other Glow-worm code.
What causes F28?
The causes of F28 fall into five groups. Vaillant's manual lists them in this order, for the engineer to work through:
- The gas. The gas tap under the boiler closed, the gas pressure too low, air in the gas or the gas valve. Air in the gas often follows a new meter or the first start.
- The air and the flue. The air intake or the flue blocked.
- The condensate. The pipe that carries water from the boiler to a drain blocked or frozen, so the water backs up.
- The ignition. The parts that make the spark (the transformer, its lead and the electrode) and the electrode that senses the flame.
- The electrics. Plugs and wiring, the earthing, and the control board.
Glow-worm's manual lists the same groups, and adds a gas meter fault and a tripped gas pressure switch. The makers don't rank the causes, so the list keeps the manual's order.
Sources: Vaillant's installation and maintenance instructions for the ecoTEC plus, Glow-worm's for the Energy7, and both makers' advice on frozen condensate pipes.
Worth knowing
A frost can freeze the condensate pipe and stop the boiler lighting, and that is one cause of F28 you can put right yourself.
What can you safely check?
The safe checks for F28 are the ones the makers' own guides give a householder. Never take the boiler's case off, and never touch anything that carries gas.
1. Is the gas on?
Try the hob or another gas appliance. On a prepayment meter, see that there is credit. The current Vaillant ecoTEC plus guide also asks you to see that the gas tap under the boiler is open.
2. Is it freezing outside?
A condensate pipe frozen in a frost can stop the boiler lighting. If the frozen part is at ground level, within reach, thaw it with warm water, never boiling, then reset. When a boiler won't fire up, and frozen condensate pipes.
3. Reset it, a few times at most
The reset key works differently by model:
- A Vaillant ecoTEC plus from before 2023, or a Glow-worm Energy7: press the reset key for a second.
- The current ecoTEC plus: hold the reset key for more than three seconds.
The guides allow three resets at most, or five on a Glow-worm Compact. If F28 comes back after that, stop.
Sources: Vaillant's and Glow-worm's user guides, their fault-code pages and their advice on frozen condensate pipes.
When should you stop and ring an engineer?
An engineer is the next step for F28 once the resets the guide allows haven't cleared it. Any one of these signs makes an engineer the next step straight away:
- The gas works everywhere else in the home and the condensate pipe isn't frozen, yet F28 keeps coming back.
- F28 comes and goes, the boiler lighting one day and not the next.
- The boiler shows F.29 or F.54 as well, which points to the gas supply.
- You'd need to open the boiler to go further.
If you smell gas, don't reset anything. Open the gold "Smell gas?" bar on this page for the free emergency number. Otherwise, ring us. Finding the cause of an F28 is a job for our Gas Safe registered engineers.
The question we'll ask when you ring about F28
Our first question about F28 is whether the hob and your other gas appliances work. That one answer splits the causes in two. If nothing gas works, the supply is the likely cause. If everything else works, the fault is in the boiler. We'll also ask for the boiler's model, from the label underneath it, and the exact code on the display.
What changes the price of the fix?
The cost of fixing F28 depends on its cause. A frozen condensate pipe or air in the gas may need no part at all. An ignition electrode or a gas valve is a part to fit. The rate is agreed on the call, before an engineer comes, and no work is done until you say yes.
Do you cover my part of London?
Yes: we fix F28 faults all over Greater London, day and night, in every borough north and south of the Thames. Pick your side of the river to see the areas.
North of the river
Every borough north of the Thames: Barnet and Enfield at the top, Hillingdon in the west, Havering in the east, and central London in between.
South of the river
Every borough south of the Thames: Richmond and Kingston in the west, Bexley in the east, and down through Croydon to Sutton and Bromley.
Questions about F28
Can I keep resetting the boiler?
The makers' guides allow three resets at most for F28, or five on a Glow-worm Compact. If F28 comes back after that, the fault needs an engineer, and resetting again won't fix it.
Is F28 dangerous?
F28 itself is the boiler keeping you safe. It stops trying to light when it can't find a flame. A smell of gas is another matter. Treat it as an emergency, open the gold "Smell gas?" bar on this page for the free number, and don't reset the boiler.
Why has F28 come back?
F28 that comes back after a reset usually means the cause is still there. It may be one of these:
- a gas supply that drops
- a condensate pipe that refreezes overnight
- a part that lights or senses the flame some of the time, but not always
An engineer tests each in turn.
How much does it cost to fix F28?
The cost of fixing F28 depends on what caused it and the part it needs, if any. The rate is agreed on the call, before an engineer comes. How our rates work.
Don't know what has failed? You don't have to.Ring and say what you can see or hear. Finding the fault is our job.
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A real person answers and gives you the rate on the call. No work starts until you say yes, and repairs are guaranteed for 12 months: parts, labour and any return visit.
