Keston E28 Fault Code: Causes, Fixes & Repair Costs
What does the Keston E28 fault code mean?
The E28 fault code on a Keston boiler indicates that the boiler's fan has failed to operate correctly. When the boiler calls for heat, it expects the fan to reach its target speed within a few seconds. If that doesn't happen — or if the control board doesn't receive the expected signal back from the fan — the boiler locks out and displays E28. The fan is a safety-critical component: its job is to push combustion gases safely out through the flue. Without a confirmed working fan, the PCB refuses to open the gas valve, so no heat or hot water is produced until the underlying fault is resolved and the boiler is manually reset.
General guidance only — not a substitute for professional advice, and not certified by a Gas Safe engineer. Always have your specific appliance assessed by a qualified professional. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
Common causes
- Faulty or seized fan motor Common
Over time, the fan motor's bearings wear out or its internal windings deteriorate, preventing the fan from spinning at the required speed. This is the most common root cause of E28. The fan may make a grinding or rattling noise before it fails completely, or it may simply stop turning without warning.
- Wiring or connector fault between PCB and fan Sometimes
The wiring loom that carries the control signal and power to the fan can suffer from loose connections, corrosion, or heat damage. If the fan isn't receiving a proper 240 V supply, or if the feedback wire back to the PCB is broken, the board will log an E28 even if the fan itself is mechanically sound.
- Blocked or obstructed venturi Sometimes
The venturi is a section of the air-gas mixing assembly that works closely with the fan. A build-up of debris or a partial blockage can prevent the fan from achieving its required airflow rate, causing the control board to detect an out-of-range fan speed and trigger a lockout.
- Faulty PCB misreading the fan signal Rare
In some cases the fan is working perfectly but the PCB is no longer interpreting the tachometer feedback signal correctly. A faulty board may believe the fan has stalled when it hasn't, resulting in a false E28 lockout. This is a less common cause and is typically identified only after the fan and wiring have been ruled out.
How to fix it
- Check that the boiler's gas supply is on DIY safe
Make sure the gas isolation valve on the gas supply pipe to the boiler is in the open position (handle in line with the pipe). Also check that other gas appliances in the property — such as a gas hob — are working normally, which confirms there is no wider gas supply outage.
- Reset the boiler once or twice DIY safe
Press and hold the reset button on the boiler's control panel as described in your user guide (usually three to five seconds). Wait for the boiler to attempt a restart. If E28 returns almost immediately, do not keep resetting repeatedly — more than two or three attempts without success will not help and may mask useful diagnostic information for your engineer.
- Listen and look at the boiler during the startup attempt DIY safe
Stand near the boiler when it tries to fire. You may be able to hear whether the fan is spinning up (a distinct hum or whirr) or whether it is silent. Note any unusual grinding, clicking, or rattling sounds. This information is genuinely useful to pass on to your engineer and can speed up diagnosis.
- Call a Gas Safe registered engineer with Keston experience Gas Safe engineer
Because E28 involves the fan — a gas-safety-critical component — all further investigation and repair must be carried out by a Gas Safe registered engineer. Keston boilers use a twin-flue design and a modulating system that not all engineers are equally familiar with, so it is worth specifically asking whether the engineer has worked on Keston appliances before. The engineer will check the voltage reaching the fan, inspect the wiring and connectors, test the fan motor directly, and examine the venturi for blockages. If the fan is at fault it will be replaced; if the wiring is damaged that will be repaired; and if the PCB is the source of the misdiagnosis it will be tested and replaced if necessary.
Parts you may need
- Boiler fan / fan motor assembly (Keston) · from £150
- Fan wiring loom / connector harness · from £35
- Venturi assembly · from £55
- Printed circuit board (PCB) · from £320
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £225–£380, depending on the underlying cause.
Frequently asked questions
Can I fix Keston E28 myself by resetting the boiler?
You can try one or two resets, and occasionally a transient glitch will clear after a single reset. However, if the fault code returns — which it almost always does when E28 is a genuine fan problem — there is nothing further a homeowner can safely do. The fan is directly connected to the safe removal of combustion gases, so any work beyond pressing the reset button must be carried out by a Gas Safe registered engineer.
How much does it cost to fix a Keston E28 fan fault in the UK?
A straightforward fan replacement — parts and labour — typically costs between £225 and £380 depending on the exact Keston model and your location in the UK. Engineers generally charge £50–£80 per hour, and a Keston fan unit itself tends to cost £100–£200. If the fault turns out to be a wiring issue rather than the fan itself, the repair may come in at the lower end of that range. A PCB replacement, if required, can add £300–£500 or more to the bill — at that point, discussing whether a new boiler makes more financial sense is well worth doing.
Is my Keston boiler dangerous if it shows E28?
The boiler has locked itself out precisely to keep you safe. It will not fire or produce a flame while E28 is active, so there is no immediate danger from gas or combustion products. You will simply have no heating or hot water until the fault is repaired. Do not attempt to bypass the lockout or interfere with the fan or flue.
My Keston boiler is over 12 years old and showing E28 — should I repair or replace it?
If the repair is limited to the fan itself, and the boiler has been regularly serviced, repair is usually the sensible choice at £225–£380. However, if the PCB also needs replacing, you could be looking at £600 or more in total — at which point a new, more efficient boiler with a manufacturer warranty often offers better long-term value. Keston's more recent Heat 2 and Combi 2 ranges are significantly more efficient than older C-series models, so the energy savings can help offset the upfront cost of replacement over a few years.