Chaffoteaux 250 Fault Code: Causes, Fixes & Repair Costs
What does the Chaffoteaux 250 fault code mean?
Fault code 250 on Chaffoteaux boilers sits within the '2xx' series, which covers the domestic hot water (DHW) circuit. Code 250 indicates that the boiler's DHW temperature sensor (NTC thermistor) is reporting an abnormal reading — this could be an open circuit, a short circuit, or a value that falls outside the expected range. When this happens, the boiler cannot reliably monitor hot water temperature and will lock out to prevent overheating or unsafe operation. Note that Chaffoteaux fault codes are model-dependent: older models use LED flash sequences rather than a numeric display, so always cross-reference your specific model's manual to confirm this code applies. If you own a Talia, Pigma, or Urbia model with a digital display, the 2xx series definitively relates to the DHW circuit. Nearby codes in the same family include 201 (DHW sensor anomaly), 203 (cylinder or tank sensor fault), and 209 (cylinder overheating), all pointing to the same sensor group.
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 degraded DHW NTC thermistor Common
The DHW NTC temperature sensor is the most common culprit. Over time these small resistive probes degrade, drift out of calibration, or fail outright — returning a reading the PCB rejects as invalid. This is particularly common on older boilers or those that have not had regular servicing.
- Loose, corroded, or damaged wiring to the sensor Common
Even if the sensor itself is fine, a poor connection at the sensor plug, a corroded terminal, or a chafed wire between the sensor and the PCB can produce exactly the same fault signal. Intermittent faults that come and go often point here rather than to the sensor itself.
- Limescale or corrosion build-up on the sensor probe Sometimes
In hard-water areas, limescale can coat the sensor probe and insulate it from the water temperature it is meant to measure, causing the reading to appear out of range. Corrosion can have a similar effect, particularly on older installations.
- PCB fault Rare
If the sensor and its wiring both test within specification, the issue may lie with the PCB's sensor-input circuitry. The board may be misinterpreting the signal or generating a spurious fault. PCB faults are less common but should be considered once all other causes have been ruled out by an engineer.
How to fix it
- Check your gas supply is on DIY safe
Confirm the gas isolation valve on the supply pipe to the boiler is fully open (handle in line with the pipe). Check that other gas appliances in the property, such as a hob or gas fire, are working normally. If there is no gas to the property, contact your gas supplier rather than the boiler manufacturer.
- Reset the boiler once DIY safe
Press the reset button on the front panel and wait around 60 seconds for the boiler to attempt a restart. If it locks out again with the same code, do not keep resetting — repeated resets on a genuine sensor fault will not clear the underlying problem and may mask a developing issue. Two to three attempts is the maximum before calling an engineer.
- Check system pressure DIY safe
Look at the pressure gauge on the boiler. The reading should sit between 1.0 and 1.5 bar when the system is cold. If it is below 1 bar, top up via the filling loop following your boiler's user guide. If pressure drops repeatedly, mention this to your engineer as it may indicate a separate issue such as a leak or a failing expansion vessel.
- Check the condensate pipe in cold weather DIY safe
If outdoor temperatures have been at or below freezing, the condensate pipe — usually a white plastic pipe that exits through an outside wall — may be frozen. Carefully pour warm (not boiling) water over the pipe or wrap it in a warm damp cloth to thaw it, then reset the boiler. This is only relevant if a condensate blockage message is also present; fault 250 alone is unlikely to be caused by a frozen condensate pipe, but it is worth ruling out.
- Have a Gas Safe engineer inspect and test the DHW NTC sensor Gas Safe engineer
A registered engineer will remove the boiler casing and use a multimeter to check the resistance of the DHW thermistor against the manufacturer's specification. A reading outside the expected range confirms the sensor needs replacing. They will also check the wiring loom and connectors for continuity and signs of corrosion or heat damage.
- Sensor replacement or cleaning Gas Safe engineer
If the sensor is confirmed faulty, the engineer will replace it with the correct part for your model. In some cases, where limescale is the cause, a thorough clean of the probe may restore correct operation, though replacement is often the more reliable long-term solution on a scaled probe.
- PCB diagnosis and replacement if required Gas Safe engineer
If the sensor and all associated wiring test correctly, the engineer should assess the PCB for any signs of burning, failed components, or intermittent signal faults. PCB replacement is a last resort but may be necessary if the board's sensor-input circuitry has failed.
- Call a Gas Safe registered engineer Gas Safe engineer
If you have completed the homeowner checks above and the fault persists, contact a Gas Safe registered engineer. Chaffoteaux boilers can be particularly involved to work on, and internal component access should only be undertaken by a qualified professional. You can verify an engineer's Gas Safe registration at gassaferegister.co.uk.
Parts you may need
- DHW NTC thermistor sensor (Chaffoteaux compatible) · from £25
- Sensor wiring loom / connector harness · from £30
- PCB (model-specific) · 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 £120–£320, depending on the underlying cause.
Frequently asked questions
Is fault code 250 always a DHW sensor problem on every Chaffoteaux boiler?
Not necessarily. Chaffoteaux fault codes vary between models, and older boilers use LED flash sequences rather than numeric codes on a screen. On digital-display models such as the Talia, Pigma, and Urbia, the 2xx series definitively covers the domestic hot water circuit, making a DHW sensor fault the most likely interpretation. However, if your boiler is an older model with indicator lights, what looks like '250' may refer to a completely different fault — always check your specific model's manual or call Chaffoteaux UK support with your model number to confirm.
Can I fix fault code 250 myself?
The initial checks — confirming your gas is on, topping up system pressure, and a single reset — are all safe for a homeowner to carry out. Beyond that, diagnosing and replacing the DHW sensor or checking the PCB requires removing the boiler casing, which must only be done by a Gas Safe registered engineer. Attempting internal repairs yourself is unsafe, likely to void any remaining warranty, and could invalidate your home insurance.
How much does it cost to fix a DHW sensor fault on a Chaffoteaux boiler?
For most homeowners, a sensor replacement including a Gas Safe engineer's labour will cost in the region of £120–£320. The sensor part itself is relatively inexpensive (typically £20–£40), but labour charges — usually £50–£80 per hour in most UK regions, higher in London — make up the bulk of the bill. If the PCB turns out to be the cause rather than the sensor, expect to pay more — a replacement board can cost £250–£450 including fitting. If your boiler is over 10–12 years old and a PCB replacement is recommended, it is worth getting a new boiler quote at the same time, as Chaffoteaux boilers typically have a serviceable lifespan of 10–15 years.
My Chaffoteaux boiler shows fault 250 but I still have heating — is that normal?
It is possible. The 250 fault relates to the domestic hot water circuit, so in some cases the central heating side may continue to function while DHW production is interrupted or unreliable. You should still have the fault investigated promptly — operating the boiler in a fault state can place additional strain on other components and may cause the boiler to lock out completely if the fault worsens.