Pressure Sensor Saunier Duval Isofast C 28 E
The pressure sensor Saunier Duval Isofast C 28 E is a sensor that measures the water pressure in the boiler circuit and sends this information to the control board. When it fails, it can cause incorrect readings, operational lockouts, and symptoms such as fault code F9 or F.73, which indicate pressure detection issues. This sensor is compatible with several models from the Isofast range, such as C24EV, C28E1, C35E, and others, as well as with models from the Isomax and Themaplus ranges, among others. It should be replaced when pressure problems or associated errors that affect the boiler's performance are detected.
VAT included
Consult via WhatsAppSaunier Duval boilers compatible with reference S57205
Pressure sensor with reference S57205. 41 verified compatibilities: C24EV and C28E.
Proven compatibility
| Boiler model | Family | Verification |
|---|---|---|
| Saunier Duval C24EV | Isofast | Contrasted |
| Saunier Duval C28E | Isofast | Contrasted |
| Saunier Duval C28E1 | Isofast | Contrasted |
| Saunier Duval C35E | Isofast | Contrasted |
| Saunier Duval C35E1 | Isofast | Contrasted |
| Saunier Duval F24E | Isofast | Contrasted |
| Saunier Duval F28E | Isofast | Contrasted |
| Saunier Duval F28E1 | Isofast | Contrasted |
| Saunier Duval F35E | Isofast | Contrasted |
| Saunier Duval F35E1 | Isofast | Contrasted |
| Saunier Duval C28E | Isomax | Contrasted |
| Saunier Duval C28E2 | Isomax | Contrasted |
| Saunier Duval F28E | Isomax | Contrasted |
| Saunier Duval F28E2 | Isomax | Contrasted |
| Saunier Duval Condens F35E | Isomax | Contrasted |
| Saunier Duval C24E | Isotwin | Contrasted |
| Saunier Duval F24E | Isotwin | Contrasted |
| Saunier Duval F28E | Isotwin | Contrasted |
| Saunier Duval Condens F30-A | Isotwin | Contrasted |
| Saunier Duval C24E | Themaplus | Contrasted |
| Saunier Duval F24E | Themaplus | Contrasted |
| Saunier Duval F25E | Themaplus | Contrasted |
| Saunier Duval F30E | Themaplus | Contrasted |
| Saunier Duval C24E | Themafast | Contrasted |
| Saunier Duval F24E | Themafast | Contrasted |
| Saunier Duval Condens F24E | Themafast | Contrasted |
| Saunier Duval Condens F30E | Themafast | Contrasted |
| Saunier Duval F24E | Themaclassic | Contrasted |
| Saunier Duval F25E | Themaclassic | Contrasted |
| Saunier Duval C24E | Themaclassic | Contrasted |
| Saunier Duval FAS24E | Themaclassic | Contrasted |
| Saunier Duval FAS25E | Themaclassic | Contrasted |
| Saunier Duval F24E | Themacondens | Contrasted |
| Saunier Duval F25 | Themacondens | Contrasted |
| Saunier Duval FAS25 | Themacondens | Contrasted |
| Saunier Duval C18E | Thematek | Contrasted |
| Saunier Duval C24E | Thematek | Contrasted |
| Saunier Duval F24E | Thematek | Contrasted |
| Saunier Duval C24E | Thema | Contrasted |
| Saunier Duval Condens F25 | Thema | Contrasted |
| Saunier Duval Condens F25 | Semia | Contrasted |
Can't see your model or have questions? The printed reference takes precedence. How to check it · Send us a photo via WhatsApp.
How to check if ref. S57205 is the part for your boiler
What determines it is not the boiler model, but the reference printed on the part you already have installed.
- Find the reference printed on the installed part and check whether it matches the catalogue reference S57205. If it is not visible, do not identify the part from its shape alone.
- Check the full boiler model on its data plate and look for it in the model associations on this page.
- Compare the connections and physical body with the original part before installation.
- If anything is unclear, send us a photo of the marking via WhatsApp before placing your order.
Symptoms and faults that the pressure switch S57205 resolves.
The pressure sensor measures the water pressure for the electronics. These are the typical symptoms and what to do:
Common symptoms and faults
- 01
The display shows a pressure different from that of the filling gauge of the boiler.
Cause: The sensor does not correctly convert the circuit pressure into an electrical signal, resulting in the PCB having incorrect data.
Compare both readings just after filling, with the boiler cold, to confirm the difference before replacing the part.
- 02
A low pressure fault code appears when starting, even though the circuit is properly filled.
Cause: The PCB receives an incorrect value from the sensor and cuts off the start as a safety measure.
Check for any visible leaks in the filling valve, bleed valves, or radiators before concluding that the sensor is faulty.
- 03
The pressure reading shakes or blinks on the screen without you having touched anything in the circuit.
Cause: A sensor with a damaged diaphragm or internal circuit provides unstable readings, even though the actual pressure is constant.
Leave the boiler unused for a while and observe if the reading stabilizes; if it continues to fluctuate, it is more likely that the problem is with the sensor rather than the circuit.
- 04
After filling the circuit, the pressure on the display does not increase or increases very little.
Cause: The sensor may not be accurately recording the actual increase in water pressure.
Confirm with the filling process (time the tap is open and expected final pressure) that enough water has actually entered.
Fault codes from Saunier Duval that this spare part resolves.
| Code | Fault | Diagnosis and solution |
|---|---|---|
| F9 | Water pressure sensor fault. | The S57205 sensor does not deliver a valid signal (loose connector, short circuit, or obstructed hydraulic connection) and the PCB does not 'see' pressure; check wiring and pressure reading in diagnostic/menu and verify that the signal changes when pressurizing. |
| F.73 | Water pressure sensor signal out of range (too low). | Interruption/short circuit of the sensor or ground in the cable; check power supply and sensor signal, continuity of the harness, and ensure the sensor port is not blocked. |
| F.74 | Water pressure sensor signal out of range (usually too high). | Short circuit at 5/24 V or internal fault of the sensor; measure the sensor output and check if it remains fixed at high; inspect wiring and clean the orifice, replacing the sensor if it does not recover. |
| F.75 | No increase in pressure detected when the pump starts (pressure sensor and/or pump). | The sensor does not detect the pressure 'spike' due to a faulty sensor or blocked intake (first rule out air/lack of water/pump); check the pressure reading during start-up in service mode and the continuity/power supply of the sensor. |
These symptoms can have more than one cause. If your boiler displays a fault code, send it to us via WhatsApp along with a photo of the labeling, and we'll tell you if this is the part.
Data sheet for Saunier Duval pressure sensor S57205
- Catalogue reference
- S57205
- Brand
- Saunier Duval
- Type of part
- Pressure sensors
- Units in stock
- 5 units
- Status
- Refurbished
- Warranty
- 1 year
- Shipping
- 1-2 business days
- Return
- 14 days
Data read on the part and in the manufacturer's documentation
What we have not been able to verify does not appear here.
- Batch number
- 0519... (cut off by the edge of the photo)
Manuals and technical documentation
Official documentation of the boiler, useful for locating the part and cross-referencing the fault codes.
- Saunier Duval Isofast C28E Manual (PDF)Document © Saunier Duval, provided as a technical reference.
Frequently asked questions about the pressure sensor S57205
Is this pressure switch suitable for the Saunier Duval Isofast C 28 E?
When should the pressure switch of the Isofast C 28 E be replaced?
Does this sensor also work for the Themaclassic F 25 E or the Themafast F 25 E?
Spare parts related to Saunier Duval Isofast
