Identify the warning, do not guess the part.
If you Saunier Duval Thema Condens 25-A show a code, copy the complete message and check the model. Here you will find the warnings from its manual and what information to provide for a review. A code guides: it does not confirm by itself which spare part is needed.
Models and version of the manual
25-A. It corresponds to Thema Condens 25-A, not to Thema MiConnect CS/1. The manual also covers AS variants: accessory notifications depend on the installation.
Consulted edition: Thema Condens 25-A / AS25-A / AS30-A manufacturer's manualThe control options, accessories, and versions may limit which notifications appear in each installation.
Locate the code on your screen.
These accesses lead to their entry in the table. They are not a classification of the most common faults: the manual does not provide incidence statistics.
- F.22
Safety shutdown: lack of water
- F.28
Start-up fault: ignition failed
- F.29
Operating fault: failed ignition attempts
- F.83
Fault: temperature adjustment in the supply and/or return temperature sensors
What to do without opening the boiler
- Note what you see.
Complete code, message, and pressure displayed by the equipment. Indicate whether it occurs when opening hot water, requesting heating, or in both cases.
- Identify the device.
Take a photo of the screen and the identification accessible without disassembling anything. Brand, model, and version help avoid confusing tables from different ranges.
- Describe how it started.
Determine whether the fault is continuous or intermittent and if there was a supply interruption or a recent intervention. If it reappears after a reset allowed by the user manual, do not chain resets.
Do not open the casing or manipulate gas, wiring, combustion, or flue gas outlet. If you smell gas, avoid flames and switches, leave the area, and notify the distributor's emergency service from a safe location; in case of immediate danger, call 112.
Documented codes table
The meaning of the warning is provided, not the repair operations reserved for qualified personnel. When the manufacturer groups several codes, the grouping is maintained; it is not interpreted as a range of numbers.
| Code | What does · source indicate? |
|---|---|
| F.00 | Interruption of the inlet temperature sensor PDF |
| F.01 | Return temperature sensor interruption PDF |
| F.10 | Short circuit in the inlet temperature sensor. PDF |
| F.11 | Short circuit in the return temperature sensor PDF |
| F.13 | Short circuit of the accumulator sensor PDF |
| F.20 | Safety shutdown: temperature limiter PDF |
| F.22 | Safety shutdown: lack of water PDF |
| F.23 | Safety shutdown: excessive temperature variation PDF |
| F.24 | Safety shutdown: temperature rise too fast PDF |
| F.26 | Fault: gas valve not functioning PDF |
| F.27 | Safety shutdown: incorrect flame detection PDF |
| F.28 | Start-up fault: ignition failed PDF |
| F.29 | Operating fault: failed ignition attempts PDF |
| F.32 | Fault: fan PDF |
| F.42 | Resistance fault coding (probably in combination with F.70) PDF |
| F.49 | Fault: eBUS PDF |
| F.52 | Fault in the connection of the circulating flow sensor PDF |
| F.53 | Fault in the circulating flow sensor PDF |
| F.54 | Gas pressure fault (in combination with F.28/F.29) PDF |
| F.56 | Fault in the regulation of the circulating flow sensor PDF |
| F.57 | Fault during comfortable safety operation PDF |
| F.61 | Gas valve control fault PDF |
| F.62 | Gas valve fault. Disconnection delay PDF |
| F.63 | EEPROM fault PDF |
| F.64 | Electronic fault / NTC PDF |
| F.65 | Fault: PCB temperature PDF |
| F.67 | Fault: electronics/flame PDF |
| F.68 | Flame signal fault (unstable) PDF |
| F.70 | Invalid product code (DSN) PDF |
| F.71 | Fault of the heating flow temperature sensor PDF |
| F.72 | Fault in the inlet and return temperature sensors. PDF |
| F.73 | Water pressure sensor signal out of range (too low) PDF |
| F.74 | Water pressure sensor signal out of range (too low) PDF |
| F.77 | Fault in flue gas damper/condensate pump PDF |
| F.79 | Accumulator temperature sensor fault PDF |
| F.83 | Fault: temperature adjustment in the supply and/or return temperature sensors PDF |
| F.84 | Fault: temperature sensor difference between supply/return, not plausible. PDF |
| F.85 | Fault: incorrect installation of the inlet or return temperature sensor PDF |
| F.86 | Fault: floor contact PDF |
Is there a problem, but no fault code appears?
The absence of a warning does not rule out a fault. For a boiler that does not heat, does not deliver hot water, loses pressure, or operates intermittently, describe the symptom and the moment it occurs. Do not assume that the PCB, the pump, or a sensor is faulty without checking the equipment and the installation.
Request a review of the boiler. · Consult maintenance
Before requesting a repair
Does the code identify the spare part I need to buy?
No. A single warning can have multiple causes. The spare part reference requires identifying the appliance and confirming the fault; the code or a generic photograph is not sufficient.
Can it be reset again if the fault returns?
It is not advisable to chain resets. Follow only what is outlined for the user in your version's manual. A persistent or recurring lockout requires inspection.
When does it make sense to compare a new boiler?
When you have a diagnosis and a budget, compare repair, availability of the spare part, and replacement according to your installation. An isolated fault code does not justify changing the equipment.
Models of this guide in the catalog
See new boilers · Consult installation or replacement
The technical sheet of each product provides information on its price and availability. Installation is quoted separately depending on the case.
Documentation and other guides
Official manual of Saunier Duval Thema Condens 25-A · Thema Condens 25-A / AS25-A / AS30-A manual. The page reference numbers in the table correspond to the PDF viewer, which may differ from the printed version.
Consult fault guides by brand and model. · Return to the blog