Chaffoteaux boiler error 108: causes and solutions

Code 108 on Chaffoteaux Inoa Green and Pigma Green boilers indicates insufficient pressure in the heating circuit and may trigger a safety shutdown. The first check is to read the pressure gauge and compare it with the model’s manual. If pressure keeps dropping, the reading appears normal or there is a leak, a qualified heating engineer should investigate: resetting does not address the cause.

If you have a problem with your boiler, you can use our free error code finder. It helps you identify errors and find clear, practical troubleshooting information.

Code 108 describes an operating condition, not a broken part

The boiler needs heating water to circulate under suitable conditions to carry heat to the radiators. When it detects insufficient pressure, it may stop operating to protect the appliance. The warning describes a condition that prevents operation, but does not identify where water is being lost or confirm that a component has failed.

This interpretation applies to the Inoa Green and Pigma Green ranges covered by the reference documentation. For other Chaffoteaux appliances, check the specific manual rather than automatically transferring the meaning between generations. The full model name, found in the paperwork or on an accessible external label, helps identify the correct appliance without removing a cover.

Some available explanations attribute this number to a main sensor fault or a combustion problem without specifying a compatible range. That discrepancy means these descriptions cannot be treated as equivalent. For the models mentioned, the relevant issue is heating circuit pressure; the warning does not justify adjusting the gas supply, cleaning the burner or replacing a sensor.

The number on the display should not be confused with a measurement, either. The 108 is an error code, whereas pressure is expressed in bar and shown on the gauge or a dedicated panel reading. Keeping these separate prevents the message from being mistaken for a pressure value and gives the engineer two distinct observations.

A cold pressure reading tells you more than repeated resets

The reference information generally places pressure in these systems between 1 and 2 bar and mentions approximately 1.2 to 1.5 bar as a guide. These are not universal settings: the model’s manual and the installation’s requirements take precedence. When assessing a drop, a reading with the system cold, with no heating demand, is particularly useful.

A reading below 1 bar is consistent with low pressure and fits the usual reason for the warning. However, it does not establish the exact activation threshold for every Chaffoteaux boiler. Nor does any reading within the general range guarantee operation: the appliance may be detecting a condition that needs further professional assessment.

Water changes volume as it heats up, so a reading taken while the heating is running should not be compared directly with one taken when the radiators are cold. Noting the conditions helps avoid a false impression of pressure loss. What matters is a downward trend under comparable conditions, rather than every small movement of the needle.

You can observe the gauge from outside the appliance with dry hands and without removing panels. If the gauge is inaccessible or a digital reading requires access to technical settings, simply record what the normal display shows. There is no need to enter installer menus to gather useful and safe information about the fault.

A small leak can explain repeated shutdowns

Drops around a radiator valve, staining beneath a joint or a damp patch on the floor are relevant clues. A slight leak may go unnoticed while gradually reducing the water in the circuit. The household check is to look at visible areas, not tighten connections, dismantle valves or search for a leak inside the boiler.

It also helps to distinguish an old damp mark from an active leak. A photograph of the area and another of the pressure gauge can document what happened without touching the installation. If water is close to cables, sockets or the inside of the appliance, do not try to dry or reach those areas: stop checking the appliance yourself and seek professional assistance.

No puddle does not mean no leak. Some pipework may be concealed, and certain leaks appear only when the circuit is hot. Pressure that drops again after being professionally restored therefore needs investigation even if the radiators look dry. The key information is the repeated pressure drop, not the size of a visible damp patch.

There is no need to operate the drain valve, radiator bleed points or any unfamiliar valve during a visual inspection. Controls beneath a boiler may belong to different circuits, and appearance alone is not enough to identify them. If a joint drips, leave it untouched and tell the engineer the exact location of the leak.

Recent radiator bleeding changes how the reading is interpreted

A warning that appears after the radiators have been bled provides an important clue. Bleeding can release water as well as air, leaving the final pressure below the required level. That timing helps guide diagnosis, but does not prove the matter is resolved: it is necessary to check whether pressure remains stable afterwards following the appropriate intervention.

Water noises or cold sections on a radiator can accompany circulation problems, but do not identify the cause of code 108 on their own. They do not prove that further bleeding is needed, either. When pressure is already low, releasing more from the circuit can make matters worse; bleeding should not become an automatic response to the shutdown.

It also matters whether the warning followed servicing, a repair or a period without using the heating. These circumstances do not necessarily mean a new fault has developed, but they help the engineer establish what changed before the problem appeared. Providing this context is more useful than automatically blaming the last component that was touched.

Heating water and the hot water supplied to taps serve different purposes within a combination boiler. Opening a hot tap does not refill the closed radiator circuit. Likewise, good flow at the kitchen tap does not show that heating pressure is correct or rule out the warning.

The expansion vessel and safety valve can leave useful clues

The expansion vessel accommodates changes in water volume as it heats up. If it is not working properly, pressure may vary more sharply than usual. A pronounced rise during heating followed by a low reading after cooling is a pattern worth investigating, but it is not enough to confirm an expansion vessel fault.

The safety valve allows water to discharge under certain overpressure conditions. If it discharges or fails to close correctly, it can contribute to low pressure afterwards. Moisture at an accessible discharge point is useful information, but does not establish whether the valve itself is responsible or whether the cause lies in another part of the circuit.

A discharge outlet must not be blocked, redirected with an improvised arrangement or disabled to retain water. It is a protective component. Checking the vessel’s charge, removing the valve or working on pressurised connections is not a household task: these operations require a qualified heating engineer and controlled working conditions.

These possibilities explain why repeatedly adding water is not the same as repairing the fault. The gauge may temporarily return to an acceptable reading while the mechanism causing the loss remains. A lasting correction requires understanding what happens between heating and cooling, rather than simply making the number disappear from the display.

Apparently normal pressure calls for a closer diagnosis

If the gauge shows a value consistent with the manual but code 108 remains, do not add water as a precaution. There may be a discrepancy between actual pressure and the information reaching the controls, or the reading may have been misinterpreted. The priority becomes verifying the measurement, not raising pressure without a clear reason.

A pressure sensor or its reading system may be involved, but that does not make every 108 warning a sensor fault. The engineer needs to distinguish genuinely low pressure from a detection problem. This avoids replacing a part that was correctly reporting a problem somewhere else.

Buying a sensor before diagnosis introduces an expense that may be difficult to justify. The error number does not provide a spare part reference, and two boilers from the same brand may use different components. Replacement decisions require full appliance identification and a confirmed component fault, not a matching error number on a shop page.

The same caution applies to the electronic control board. An unsuccessful reset does not prove the board is damaged, just as an illuminated display does not rule out other faults. Internal checks of sensors, wiring and electronics belong to the engineer; from outside, the most useful evidence is the reading, code and observed behaviour.

Restoring pressure is not a matter of trying unfamiliar controls

When a shortage of water is confirmed, restoring operation may require controlled replenishment followed by a check for leaks. The reference documentation describes filling as a possible correction, but it involves pressurised water. The boundary is clear: do not handle pressurised connections or guess which control is the filling valve.

A guide value of 1.5 bar is not a universal instruction for every installation. The correct pressure depends on the manufacturer’s requirements and the circuit configuration. An engineer can establish whether restoring pressure is sufficient or whether a leak, discharge or pressure detection problem must be addressed first.

A reset using the normal user control only makes sense where the manual allows it and the conditions causing the shutdown have been resolved. There is no need to open the appliance, disconnect wiring or work at the electrical distribution board. If the warning returns, repeating the reset provides no new diagnosis and cannot replace correcting the underlying cause.

If the model is unknown, the reading cannot be clearly identified or water is coming from the appliance, leave further intervention to a professional. Keeping a record of the code and avoiding adjustments helps the subsequent assessment. Household checks end where removing the casing, changing technical settings or working on the water circuit becomes necessary.

Hot water at the tap does not confirm that everything is working

Domestic hot water behaviour depends on the model and how its protective controls operate. In some circumstances, the heating may stop while hot water remains available, but this is not a rule for every range. One service remaining available does not prove that the pressure problem has cleared.

If the boiler remains locked out or displays the warning again, do not try to force the heating to run through repeated resets. The protective function is there to prevent operation outside the intended conditions. Even if the appliance starts intermittently, that does not make recurring pressure loss acceptable.

To stop using the appliance, use its normal control only if it is accessible and the surrounding area is dry. If water is leaking onto electrical parts, do not touch the appliance or its connections. The aim is not to resolve an unsafe situation from outside, but to keep a safe distance from the wet area until it has been assessed.

Code 108 alone does not demonstrate a gas leak, either. If there is also a smell of gas, follow the gas supplier’s emergency instructions and avoid operating electrical switches or creating flames. This should not be treated as a simple extension of the pressure problem: these are different types of warning sign requiring separate attention.

A specific diagnosis prevents spending money on the wrong repair

Before a visit, it helps to have the full model name, a photograph of the code and the pressure observed when cold. Details of recent radiator bleeding, servicing or visible leaks are also useful. There is no need to recreate the fault to document it: an account of what happened during normal use of the appliance is generally enough to start with.

The cost cannot be inferred from code 108. An accessible external leak, a reading fault and an expansion vessel problem involve different work. A fixed figure without identifying the cause would therefore be unreliable. The useful comparison is between quotations covering the same diagnosis and scope, rather than amounts with no supporting detail.

Before agreeing to work, establish whether travel and diagnosis are charged separately and whether those charges are deducted if the repair goes ahead. The proposed replacement part and the reason for replacing it should also be explained. Do not assume that every company uses the same terms or that an initial visit includes the repair.

The code does not automatically mean the whole boiler needs replacing. That decision requires consideration of its overall condition, breakdown history, spare parts availability and the confirmed scope of the work. A pressure warning alone does not show that the appliance has reached the end of its life; replacement without diagnosis can turn a localised problem into an unnecessarily large expense.

Stable pressure is the outcome that matters

A repair is not judged solely by whether the warning disappears at the end of the visit. Pressure should also behave consistently during subsequent use, without further leaks. The engineer should explain what has been corrected and which observations to report if the shutdown returns, without expecting the user to carry out internal appliance checks.

After work has been completed, a single reading says less than the pattern under comparable conditions. Occasionally recording the cold pressure can help if the problem returns, but there is no need to watch the display continuously. What matters is recognising and reporting a persistent change, while avoiding further filling or adjustments on your own.

On Chaffoteaux Inoa Green and Pigma Green boilers, code 108 points first towards insufficient pressure. The gauge, maintenance history and external signs help guide the assessment without dismantling anything. If the reading is normal, drops again or leaks appear, the next step is professional diagnosis of the circuit, not a succession of household experiments.

The difference between clearing a warning and resolving a fault is that the appliance returns to stable operating conditions. Reading before acting, following the specific manual and avoiding assumptions about a particular component prevent misinterpretation. Here, the most useful information is not a reset trick, but knowing where safe checks end.