Chaffoteaux 211 Fault Code: Causes, Fixes & Repair Costs
What does the Chaffoteaux 211 fault code mean?
Fault code 211 on a Chaffoteaux boiler means the boiler's control system has detected a problem with the central heating return temperature probe — an NTC thermistor that monitors the temperature of water flowing back into the boiler from the heating circuit. Chaffoteaux uses a prefix numbering system for its fault codes: the leading '2' identifies this fault as belonging to the DHW and secondary circuit sensor group, while '11' pinpoints this specific return probe. When the control board receives a reading from this probe that is out of range, missing entirely, or suggests a short or open circuit, it logs code 211 and locks out to prevent unsafe operation. In most cases this turns out to be a faulty or degraded NTC sensor — a relatively inexpensive part — though damaged wiring or, less commonly, a faulty PCB can produce the same code.
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 or degraded NTC return probe Common
The CH return NTC thermistor has either broken down internally or drifted so far out of its calibrated resistance range that the control board can no longer trust its readings. At around 25°C a healthy Chaffoteaux NTC probe should measure roughly 1.2–17.3 kΩ; a reading of zero ohms points to a short circuit and a reading of infinity points to an open circuit — both mean the probe must be replaced.
- Loose, corroded, or broken wiring connections Common
The low-voltage wiring between the NTC probe and the PCB is susceptible to corrosion, vibration fatigue, and connector loosening over time. Even a slightly high-resistance connection can push the signal outside the acceptable window and trigger code 211, even though the probe itself is physically intact.
- Short circuit or open circuit in the sensor circuit Sometimes
A break in the cable insulation, a pinched wire, or water ingress near a connector can create either a short to earth or a complete break in the sensor circuit. The control board interprets either condition as a damaged probe and raises the fault.
- Faulty PCB (control board) Sometimes
If the NTC probe and all associated wiring test correctly but the fault persists, the control board itself may be misreading the signal due to a failed input circuit. Visual signs of PCB failure include discolouration, swollen capacitors, or burn marks, though internal failures can be invisible.
- Mains supply voltage issues Rare
Significant voltage spikes or sustained supply irregularities can corrupt the control board's sensor readings or cause transient faults that appear as probe errors. A stabilised supply or UPS can help protect against this on repeat occurrences.
How to fix it
- Attempt a single boiler reset DIY safe
Locate the reset button on the boiler's front panel and press it once. A transient glitch can sometimes clear after a reset. If code 211 returns immediately or after the next heating demand, do not keep resetting — repeated resets will not fix a genuine sensor fault and may mask useful diagnostic information for your engineer.
- Check the mains polarity DIY safe
If the fault appeared after the boiler was disconnected from power and reconnected, try rotating the mains plug 180° in the socket and powering the boiler back on. This is a quick polarity check that can rule out an incorrectly wired socket contributing to control board errors.
- Engage a Gas Safe registered engineer to test the NTC probe resistance Gas Safe engineer
An engineer will isolate the boiler from the mains, locate the CH return NTC probe, disconnect it from its connector, and measure its resistance with a multimeter. A reading at room temperature that is zero ohms (short circuit) or effectively infinite (open circuit) confirms the probe has failed and must be replaced.
- Replace the CH return NTC probe if it tests faulty Gas Safe engineer
A Chaffoteaux-compatible NTC thermistor (Ariston Group part 61000733 or equivalent) is widely available from UK boiler parts suppliers at roughly £11–£40 depending on the specific model variant. The engineer will drain the relevant circuit section, swap the probe, and verify the new reading is within the correct resistance range before refilling and testing.
- Inspect all wiring and connectors between the probe and the PCB Gas Safe engineer
If the probe tests within specification, the engineer should check the full cable run for chafed insulation, corroded terminals, and loose connector pins. A damaged wire or a connector that has worked loose through vibration can produce exactly the same fault code as a failed probe.
- Investigate the PCB if probe and wiring are both serviceable Gas Safe engineer
Should the probe and all wiring prove sound, the control board becomes the prime suspect. The engineer will inspect the board for visible damage such as burn marks, deformed components, or broken tracks, and may substitute a known-good board to confirm the diagnosis before quoting for a replacement.
- Call a Gas Safe registered engineer if you have not already done so DIY safe
Code 211 requires component-level diagnosis and likely a parts replacement that must be carried out by a Gas Safe registered engineer. Contact one promptly — particularly if this is your only source of heating or hot water. Ask for a written fixed-price quote before authorising any work.
Parts you may need
- CH return NTC thermistor probe (Ariston/Chaffoteaux compatible, e.g. part 61000733) · from £15
- Wiring loom / sensor harness · from £35
- PCB / control board (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–£300, depending on the underlying cause.
Frequently asked questions
Is fault code 211 dangerous — will it damage my boiler if I leave it?
The boiler locks out when it raises code 211 precisely to protect itself: running without a reliable return temperature reading could allow the heating circuit to overheat. You should not attempt to keep resetting the boiler to keep it running. While the fault itself is an electrical/sensor issue rather than a gas-safety concern, leaving it unattended means you risk going without heating or hot water and potentially causing secondary damage. Book an engineer promptly.
How much does it cost to fix a Chaffoteaux 211 fault in the UK?
For most people this fault is resolved by replacing the NTC return probe — a straightforward repair that typically costs £120–£300 including the engineer's call-out, labour, and the part itself. If the PCB turns out to be at fault rather than the probe, costs rise considerably: a replacement control board plus fitting can run to £350–£500 or more depending on model and region. London and South East prices tend to run 15–25% above the national average. Always get a written fixed-price quote before work begins.
Can I replace the NTC probe myself to save money?
Although the NTC probe is an electrical component rather than a gas-carrying one, accessing and replacing it on a Chaffoteaux boiler requires draining part of the sealed system, dismantling internal boiler components, and correctly refilling and re-pressurising the system afterwards. In practice most insurers and boiler warranty providers require a Gas Safe registered engineer to carry out internal boiler work. Attempting it yourself could also void any remaining warranty. We recommend using a Gas Safe engineer for this repair.
Why does Chaffoteaux start its fault codes with a number like '2'?
Chaffoteaux uses a prefix-based fault code system where the first digit indicates which functional group of the boiler is involved. The '2' prefix covers faults related to the DHW and secondary or solar circuit sensor group — so any code in the 200s relates to a temperature sensor or probe fault in that circuit. The second part of the code (here '11') then identifies the specific probe or sensor involved. This means if your display shows '211' you can immediately narrow the fault down to the central heating return probe on the system or solar module.