Chaffoteaux 5P2 Fault Code: Causes, Fixes & Repair Costs
What does the Chaffoteaux 5P2 fault code mean?
The 5P2 code appears on Chaffoteaux boilers when the burner fails to light on its second ignition attempt — or, in some cases, when the boiler successfully ignited on that second try and has simply logged the event as a notification. Chaffoteaux boilers work through a staged ignition sequence: a first attempt is logged as 5P1, a second as 5P2, and a third failed attempt as 5P3. If ignition succeeds at any stage, the sequence stops there, so 5P2 does not always mean a fault is ongoing. However, 5P2 is classed as a non-volatile error, which means the boiler will not restart automatically — you must manually reset it. The display can be confusing because the digit '5' closely resembles the letter 'S', leading many users to read the code as SP2 rather than 5P2; both refer to the same fault. If repeated resets fail to clear the lockout, an underlying component or supply issue is almost certainly to blame.
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
- Gas supply interrupted or insufficient pressure Common
If the gas supply to the property is off, low, or the meter credit has run out, the boiler cannot establish a flame on any attempt. This is the most common explanation, especially after a supply interruption or very cold weather when demand on the network is high.
- Frozen condensate pipe Common
In cold weather, the external condensate pipe — usually a white plastic pipe exiting through an outside wall — can freeze solid, causing the boiler to lock out. This is a very common winter cause and is straightforward to thaw safely yourself.
- Low system water pressure Common
Most Chaffoteaux boilers require at least 1 bar of water pressure to operate safely. If the pressure gauge reads below 1 bar, the control board will prevent ignition as a protective measure. The pressure gauge is usually visible through the boiler's front panel.
- Dirty or faulty ignition electrode Common
The ignition electrode generates the spark that lights the burner. Over time it can become coated with carbon deposits or physically damaged, preventing a reliable spark. This is a routine finding on boilers that have not been serviced recently.
- Dirty or mispositioned ionisation (flame-sensing) electrode Common
Even if the burner lights successfully, the flame must be detected by the ionisation electrode. If this probe is sooty, cracked, or slightly out of position, the control board receives no confirmation of a flame and shuts down — triggering the 5P2 lockout. The boiler may briefly light and then cut out.
- Flue or ventilation obstruction Sometimes
A blocked flue terminal, a bird's nest in the flue, or covered ventilation grilles around the boiler can restrict airflow sufficiently to prevent safe ignition. The control board detects the problem and locks out before allowing unburnt gas to accumulate.
- Gas valve malfunction Sometimes
The gas valve controls the flow of gas into the burner and is operated by signals from the PCB. A valve that is sticking, electrically faulty, or has drifted out of specification will prevent gas reaching the burner even when ignition is attempted. This is confirmed by resistance and voltage checks carried out by an engineer.
- PCB (printed circuit board) fault Rare
The PCB coordinates the entire ignition sequence. A faulty or dirty board may fail to send the correct signals to the ignition electrode or gas valve, causing every attempt to fail even when all other components are serviceable.
How to fix it
- Check your gas supply at other appliances DIY safe
Turn on a gas hob or check another gas appliance in the property. If nothing works, the issue is with your gas supply rather than the boiler. Contact your gas supplier or check any prepayment meter credit before going any further.
- Check the system pressure gauge DIY safe
Locate the pressure gauge on the boiler — it is typically visible through the front panel or on the pipework below the boiler. It should read between 1.0 and 1.5 bar when the system is cold. If it reads below 1 bar, repressurise using the filling loop (usually a flexible braided hose with one or two valves beneath the boiler). Open the valve(s) slowly, watch the gauge rise, and close the valve(s) once you reach about 1.2 bar. Do not overpressurise beyond 1.5 bar.
- Check for a frozen condensate pipe DIY safe
In cold weather, look outside for a white plastic pipe (typically 21.5 mm or 32 mm diameter) exiting through an outside wall, often near the boiler. If it looks iced up or you can feel a solid blockage, thaw it gently using warm — not boiling — water poured over the pipe, or a warm cloth wrapped around it. A hot-water bottle held against the pipe also works. Once thawed, reset the boiler.
- Check ventilation grilles are clear DIY safe
Look at the grilles or louvres around the boiler casing and any permanent ventilation in the room. If they are clogged with dust or lint, carefully vacuum or wipe them clean with a dry cloth. Restricted airflow can prevent the boiler from completing the ignition sequence safely.
- Attempt a single reset DIY safe
Press and hold the reset button (refer to your boiler's user guide for its exact location — it is often marked with a flame or restart symbol) for around three seconds. Wait for the boiler to attempt ignition. If it lights and runs normally, monitor it over the next few hours. Important: limit yourself to no more than two or three resets in total. Chaffoteaux boilers log excessive resets and can trigger a separate lockout (error 304) if the reset button is pressed too many times in a short period.
- Power-cycle the boiler DIY safe
Switch off the boiler at its electrical isolator or fuse spur, wait at least ten seconds, then restore power. Once the display lights up again, press the reset button. This can clear transient electronic faults that a standard reset does not resolve.
- Call a Gas Safe registered engineer if the fault persists Gas Safe engineer
If the boiler locks out again after your reset attempts, or if you cannot identify an obvious cause such as low pressure or a frozen pipe, a Gas Safe registered engineer must attend. They will inspect and clean the ignition and ionisation electrodes, test gas valve operation and measure electrical values across its coils, check the PCB outputs, verify gas inlet pressure with a manometer, and inspect the flue for obstructions. Do not attempt to access gas components, electrodes, the gas valve, or the PCB yourself.
Parts you may need
- Ignition electrode · from £45
- Ionisation (flame-sensing) electrode · from £40
- Gas valve · from £220
- PCB (control board) · from £280
- Flue fan / ventilation unit · from £180
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–£350, depending on the underlying cause.
Frequently asked questions
Is 5P2 the same as SP2 on a Chaffoteaux boiler?
Yes — they are exactly the same code. The seven-segment display on many Chaffoteaux boilers renders the digit '5' in a way that looks almost identical to the letter 'S', so the same notification can appear as either 5P2 or SP2 depending on how you read it. Both refer to the second ignition attempt in the boiler's ignition sequence.
My Chaffoteaux boiler is showing 5P2 but seems to be running fine — do I still need to worry?
Not necessarily. If the boiler is running normally and producing heat and hot water, it is likely that ignition succeeded on the second attempt and 5P2 is simply a logged notification rather than an active fault. Clear it with a single reset. If it keeps returning, book a service — recurring second-attempt ignitions usually mean a deteriorating electrode, slightly low gas pressure, or another developing component issue worth catching early.
How many times can I reset a Chaffoteaux boiler showing 5P2?
Keep resets to a maximum of two or three attempts. Chaffoteaux control boards monitor reset frequency, and pressing reset more than around five times in a fifteen-minute window can trigger a separate lockout code (error 304 — too many resets), which will extend the time before the boiler can attempt ignition again. If the boiler locks out again after two resets, stop and call a Gas Safe engineer rather than continuing to reset.
What does a 5P2 repair typically cost in the UK?
For the most common causes — cleaning or replacing an ignition or ionisation electrode — expect to pay roughly £150 to £250 including labour. If the gas valve needs replacing, costs typically rise to £300–£450 once parts and labour are included. A new PCB is at the higher end and can reach £400–£500 fitted; if your boiler is over ten to twelve years old and needs a PCB or fan assembly, it is worth getting a boiler replacement quote alongside the repair quote, as a new boiler may prove more cost-effective in the long run.