Chaffoteaux 241 Fault Code: Causes, Fixes & Repair Costs
What does the Chaffoteaux 241 fault code mean?
Fault code 241 on Chaffoteaux appliances points to a sensor or detection circuit that has gone open-circuit — but the exact component depends on which model you own. On gas combi and system boilers (such as the Britony and Minima HE ranges), code 241 indicates that the domestic hot water (DHW) NTC thermistor has lost its electrical signal, meaning the boiler's hot water temperature sensor is either internally failed, disconnected, or has a broken wire. On the AquaNext Plus 250 heat-pump water heater, the same code flags an open-circuit fault on the imposed-current sacrificial anode, with both the resistance heater and heat pump disabled as a safety response. In both cases the boiler or appliance locks out because it cannot safely monitor or control the relevant circuit. Check your model number before proceeding — the diagnostic steps differ between product families.
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
- Failed DHW NTC thermistor (gas boiler models) Common
The domestic hot water temperature sensor is a small NTC thermistor whose electrical resistance changes predictably with water temperature. Over time, heat cycling and limescale build-up can degrade the sensor element internally, causing its resistance to rise to an open-circuit level. The PCB sees no valid signal and triggers a lockout. This is the most frequent cause of code 241 on Chaffoteaux gas boilers.
- Loose or damaged wiring to the DHW sensor Common
Even if the thermistor itself is healthy, a corroded connector, a chafed wire, or a plug that has vibrated loose from the PCB header will produce the same open-circuit reading. Engineers often find a broken pin or pushed-back terminal in the sensor's Molex connector, particularly on older installations.
- Open-circuit anode or anode wiring fault (AquaNext Plus 250 only) Common
On the AquaNext Plus 250, the imposed-current anode protects the tank from corrosion by passing a small electrical current. If the anode element fails internally, its mounting wire becomes disconnected, or the wiring loom to the motherboard develops a break, the control board detects an open circuit and shuts down both heating modes. The fix involves checking continuity of the anode circuit and its connector at the motherboard.
- Limescale deposits on the heat exchanger or sensor pocket Sometimes
In hard-water areas, mineral scale can insulate the sensor from the water temperature it is trying to measure, pushing readings out of range. Severe scaling can also restrict flow enough to cause erratic temperature signals that are interpreted as a sensor fault.
- Faulty PCB or motherboard Rare
If the sensor and wiring test correctly but the fault code persists, the issue may lie with the PCB (gas boilers) or motherboard (AquaNext) itself — either a damaged input channel or a failed reference voltage. This is a less common cause but should be investigated once the sensor and wiring have been ruled out.
How to fix it
- Check your boiler model and note which version of the fault applies DIY safe
Look at the rating plate on the front or inner casing of your appliance. If you own a Britony, Minima HE, or similar gas combi/system boiler, you are likely dealing with a DHW thermistor fault. If you own an AquaNext Plus 250, the fault relates to the anode circuit. Knowing this will help you describe the issue accurately to an engineer and avoid unnecessary part orders.
- Reset the boiler once and observe whether the fault returns DIY safe
Locate the reset button (usually marked with a flame or the letter R) and press it firmly for around three seconds. Allow the boiler two to three minutes to attempt a restart. If the fault code reappears promptly, do not keep resetting — repeated resets will not clear a component fault and can mask underlying problems. One or two attempts is the safe limit.
- Check system pressure (gas boiler models) DIY safe
Glance at the pressure gauge on the boiler fascia. At cold, the needle should sit between 1.0 and 1.5 bar. If it reads below 1 bar, repressurise via the filling loop — consult your boiler's user guide for the correct procedure. Low pressure alone will not cause code 241, but it is worth correcting before an engineer visits so it does not complicate diagnosis.
- Check that the gas supply to your home is working DIY safe
Turn on a gas hob ring. If it lights normally, your gas supply is fine. If there is no gas at the hob either, contact your gas supplier before calling a boiler engineer. A gas supply interruption can cause lockout codes that clear once supply is restored.
- Engineer to inspect and test the DHW NTC thermistor (gas boiler models) Gas Safe engineer
A Gas Safe registered engineer will use a multimeter to measure the thermistor's resistance across its two terminals and compare the reading against the manufacturer's resistance-temperature curve. A healthy NTC sensor will show decreasing resistance as temperature rises (typically several kilohms at room temperature). A reading of infinite resistance (open circuit) or one far outside the expected range confirms sensor failure. The sensor is usually clipped into a pocket on the DHW heat exchanger or plate heat exchanger.
- Engineer to check all wiring and connectors in the sensor circuit Gas Safe engineer
Before condemning the thermistor, the engineer will inspect the full wiring loom from the sensor to the PCB — checking for corroded pins, pushed-back terminals, heat-damaged insulation, and secure connector seating. A continuity test along each wire confirms whether the fault is in the sensor or the harness.
- Engineer to verify anode circuit continuity (AquaNext Plus 250 only) Gas Safe engineer
For the AquaNext Plus 250, the engineer should confirm there is water present in the tank, then check the imposed-current anode for continuity and inspect the wiring from the anode to its motherboard connector. A broken wire, loose spade terminal, or faulty anode element will all produce code 241. If the anode and wiring are intact, the motherboard itself is the next suspect and should be replaced.
- Engineer to replace the faulty component and clear the fault Gas Safe engineer
Once the defective part is confirmed — most commonly the DHW NTC thermistor on gas models, or the anode/motherboard on the AquaNext — the engineer will fit the correct replacement part, clear the lockout, and run the appliance through a full hot water demand cycle to confirm the fault has been resolved and all temperatures are reading correctly.
- If the fault persists after sensor and wiring replacement, arrange PCB investigation Gas Safe engineer
A persistent code 241 despite a new sensor and good wiring points to a damaged input circuit on the PCB (gas boilers) or motherboard (AquaNext). PCB replacement is a significant cost, so a good engineer will bench-test the board or obtain a second opinion before committing to this repair. Call a Gas Safe registered engineer if you have not already done so.
Parts you may need
- DHW NTC thermistor sensor · from £18
- Sensor wiring harness / loom · from £35
- Imposed-current anode (AquaNext Plus 250) · from £45
- PCB / motherboard · from £280
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 £110–£320, depending on the underlying cause.
Frequently asked questions
Can I reset the boiler myself to clear code 241?
You can try a single reset — press and hold the reset button for a few seconds and give the boiler a couple of minutes to restart. If code 241 comes straight back, stop resetting. The fault is pointing to a hardware problem (a failed sensor, broken wire, or faulty anode) that repeated resets will not fix. Continuing to force restarts can cause further issues and makes an engineer's diagnosis harder.
How long does it take to replace a DHW thermistor, and is it expensive?
Replacing a DHW NTC thermistor is usually a straightforward job for an engineer — typically 30 to 60 minutes. The sensor itself costs roughly £10–£25 for most Chaffoteaux models, and combined with a standard call-out and labour charge the total bill is usually in the region of £110 to £200. This is one of the less costly boiler repairs when the wiring is also sound.
Could code 241 be a PCB problem rather than a sensor fault?
Yes, though it is much less common. If the engineer tests the thermistor and finds it within its correct resistance range, and the wiring is also undamaged, the fault may lie with the PCB's sensor input channel. A PCB for a Chaffoteaux gas boiler typically costs £180 to £350 for the part alone, plus labour — so a good engineer will always rule out the cheaper sensor and wiring options first before recommending a board replacement.
I have an AquaNext Plus 250 — why does code 241 mean something different on my appliance?
The AquaNext Plus 250 is a heat-pump water heater rather than a gas boiler, so its fault codes refer to different components. On this model, code 241 flags an open-circuit fault on the imposed-current sacrificial anode — a component that protects the stainless-steel tank from corrosion. The fault shuts down both the heat pump and the backup resistance element as a precaution. An engineer will check that the tank contains water, test the anode for continuity, inspect its wiring to the motherboard connector, and replace the anode or motherboard as needed.