Ferroli A50 Fault Code: Causes, Fixes & Repair Costs
What does the Ferroli A50 fault code mean?
The A50 code is a lockout fault on Ferroli boilers — most notably the DOMIcondens HE 26 C — indicating that the boiler's control board has detected a problem with the gas valve and has shut the appliance down as a safety precaution. Because it begins with 'A', it will not clear on its own; a manual reset is required after the underlying cause has been resolved. The boiler locks out rather than attempting to continue firing, because any uncontrolled or undetected issue with the gas valve carries a genuine safety risk. A Gas Safe registered engineer is needed to diagnose and fix the root cause before the boiler will run reliably again.
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 worn gas valve Common
The gas valve itself has failed mechanically or electrically. Over time, internal components wear, seals degrade, or the solenoid coil fails, preventing the valve from opening or closing correctly. This is the most direct cause of an A50 lockout and typically requires valve replacement.
- Wiring or connector fault between PCB and gas valve Common
A loose, corroded, or broken connection in the wiring loom running between the printed circuit board and the gas valve means the PCB cannot send or receive the correct signals to operate the valve safely. The boiler then locks out as a precaution. This is often found before condemning the valve itself.
- PCB (printed circuit board) fault Sometimes
If the control board itself is generating incorrect output signals or has suffered component failure, it may incorrectly drive — or fail to drive — the gas valve, triggering an A50 lockout. An engineer will rule out wiring and valve issues before diagnosing a PCB fault.
- Blocked or mechanically seized gas valve Sometimes
Debris, scale, or a manufacturing defect can cause the gas valve to stick in the open or closed position. The boiler's safety logic detects the abnormal response and triggers the lockout.
- Low or interrupted gas supply Rare
While insufficient gas supply more commonly produces codes such as A01, a severely restricted or interrupted supply can cause the valve and ignition sequence to behave abnormally, contributing to an A50 condition. Always verify your gas supply first before assuming a valve fault.
How to fix it
- Check your gas supply is working DIY safe
Try lighting a gas hob or another gas appliance in your home. If nothing lights, the issue is upstream of your boiler — contact your gas supplier or check whether your meter's emergency control valve is open. There is no point calling a boiler engineer until gas flow is confirmed.
- Attempt a single boiler reset DIY safe
If your gas supply is normal, press and hold the reset button (usually labelled 'R' or marked with a reset symbol) for around 5–10 seconds. Release it and allow the boiler to complete its ignition sequence. If the A50 code clears and the boiler fires up normally, monitor it over the next day or two. If the fault returns, do not keep resetting — repeated lockouts on a gas valve fault can indicate a genuine safety issue and persistent resets will not resolve the underlying problem.
- If the fault persists, call a Gas Safe registered engineer Gas Safe engineer
An A50 fault that does not clear after a single reset — or that returns shortly afterwards — requires professional diagnosis. Do not attempt to inspect, test, or touch the gas valve, wiring loom, or PCB yourself. Gas valve work is a notifiable gas fitting under UK legislation and must only be carried out by a Gas Safe registered engineer.
- Engineer inspects wiring loom and connectors Gas Safe engineer
The engineer will systematically check the wiring harness between the PCB and the gas valve for loose pins, corrosion, chafing, or open-circuit conditions. This is the quickest and cheapest fix if found — sometimes a connector simply needs reseating or a short section of loom replacing.
- Engineer tests the gas valve electrically Gas Safe engineer
Using a multimeter, the engineer will check that the valve solenoids are receiving the correct voltage signal from the PCB and that their resistance readings fall within the manufacturer's specification. A valve that fails to respond correctly or shows an out-of-range resistance is condemned and scheduled for replacement.
- Engineer replaces the gas valve if defective Gas Safe engineer
A like-for-like Ferroli gas valve is fitted, gas connections are tightened and leak-tested with a soapy solution or electronic detector, and the boiler is commissioned to verify correct gas rate and combustion. This is the most common repair outcome for a persistent A50 fault.
- Engineer assesses and replaces the PCB if required Gas Safe engineer
If the wiring and valve both test satisfactory, the fault lies with the control board. The engineer will confirm this with further electrical testing before fitting a replacement PCB, as it is an expensive component and misdiagnosis is costly. After fitting, the boiler is fully recommissioned and all safety checks are repeated.
Parts you may need
- Ferroli gas valve (DOMIcondens HE 26 C compatible) · from £120
- PCB / control board · from £150
- Wiring loom / harness · from £35
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 £150–£380, depending on the underlying cause.
Frequently asked questions
Can I reset a Ferroli A50 fault myself?
Yes, a single reset attempt is a reasonable first step and is safe to carry out yourself. Press and hold the reset button for 5–10 seconds. If the boiler fires and runs normally, monitor it closely. However, if the fault returns within a short time, stop resetting — the A50 code relates to the gas valve, which is a safety-critical component. Repeated resets without fixing the underlying cause can mask a genuine hazard and will not resolve the problem. At that point you need a Gas Safe registered engineer.
How much does it cost to fix a Ferroli A50 fault in the UK?
Most homeowners pay somewhere between £150 and £380 all-in, depending on what the engineer finds. A wiring or connection repair at the lower end of that range can cost £80–£150 including the call-out. Gas valve replacement — the most common repair — typically runs £250–£350 including parts and labour. If the PCB also needs replacing, expect to add a further £200–£300, though this is less common. On older or discontinued Ferroli models, parts availability can add to lead times and occasionally to cost.
Is the Ferroli A50 fault dangerous?
The boiler has locked itself out precisely to prevent a dangerous situation, so as long as you leave it locked out and do not repeatedly override it with resets, the immediate risk is low. However, if you smell gas at any point, do not operate any switches or appliances — leave the property immediately and call the National Gas Emergency Service on 0800 111 999 (free, 24 hours). Once the smell is investigated and cleared, a Gas Safe engineer can then address the A50 fault.
My Ferroli is over 10 years old — should I repair or replace it?
The A50 fault involves the gas valve, which is one of the most important components in the boiler. If your Ferroli is more than 10 years old and a repair quote is coming in at £300 or more, it is worth getting a replacement boiler quote at the same time. A rough rule of thumb used by many engineers is that if a single repair costs more than around 30–40% of a new boiler installation, replacement usually makes better financial sense — especially as an older boiler will be less efficient and may produce further faults before long.