3-Way Valve Motor Saunier Duval Isofast/Themafast - Ref. S1025500
The 3-way valve switches the water between the heating circuit and the domestic hot water circuit in your boiler. If it fails, you will notice that you have hot water but no heating, or vice versa, and there may even be mixing between both circuits. This 3-way valve motor from Saunier Duval, with reference S1025500, is compatible with models from the Isofast, Isomax, Isotwin, and Themafast ranges, such as the F 25 E, F 30 E, and C 35 E, among others. It is recommended to replace it when the fault code F.20 appears, which indicates a safety disconnection due to a temperature limiter.
VAT included
Consult via WhatsAppSaunier Duval boilers compatible with reference S1025500
3-way valve with reference S1025500. 18 verified compatibilities: F 35 E-A and F 30 E-A.
Proven compatibility
| Boiler model | Family | Verification |
|---|---|---|
| Saunier Duval F 35 E-A | Isofast | Contrasted |
| Saunier Duval F 30 E-A | Isofast | Contrasted |
| Saunier Duval C 35 E-A | Isofast | Contrasted |
| Saunier Duval F 35 E H-MOD | Isofast | Contrasted |
| Saunier Duval F 30 E H-MOD | Isofast | Contrasted |
| Saunier Duval Condens F 30 E | Isofast | Contrasted |
| Saunier Duval Condens F 35 E | Isofast | Contrasted |
| Saunier Duval F 35 E | Isomax | Contrasted |
| Saunier Duval F 35 H-MOD | Isomax | Contrasted |
| Saunier Duval Condens F 35 E | Isomax | Contrasted |
| Saunier Duval F 30 H-MOD | Isotwin | Contrasted |
| Saunier Duval Condens F 30 E | Isotwin | Contrasted |
| Saunier Duval F 25 E | Themafast | Contrasted |
| Saunier Duval F 30 E | Themafast | Contrasted |
| Saunier Duval C 25 E | Themafast | Contrasted |
| Saunier Duval C 30 E | Themafast | Contrasted |
| Saunier Duval Condens F 25 | Themafast | Contrasted |
| Saunier Duval Condens F 30 | Themafast | 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. S1025500 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 S1025500. 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 S1025500 three-way valve resolves.
The 3-way valve diverts water between heating and domestic hot water. These are the typical symptoms and what to do:
Common symptoms and faults
- 01
The boiler provides domestic hot water or heating, but never both at the same time when it should.
Cause: The actuator motor does not complete the rotation and the valve remains stuck in a single position.
Check the actuator when requesting domestic hot water: if you don't see or hear it turning, first check that it is receiving power at the connector.
- 02
The valve motor is making noise or buzzing but is not able to move the mechanism.
Cause: The internal gear of the actuator is worn out or the shutter is stuck due to limescale, and the motor does not have enough torque to overcome it.
If the actuator can be separated from the body, check if it turns freely when not under load; if it turns freely without the valve, the problem may be in the body, not in the motor.
- 03
The boiler does not switch properly between heating and domestic hot water, and sometimes it gets stuck in between.
Cause: The actuator loses synchronization with the actual position of the shutter.
Force a complete cycle of domestic hot water and another of heating consecutively and check if the fault occurs consistently or only sometimes.
- 04
Water leak at the area where the actuator connects to the valve body.
Cause: The gasket between the motor and the hydraulic body has failed and water is rising towards the electrical part.
If you see moisture on the actuator, do not turn on the boiler until you dry it and locate the source: a leak there can also damage the motor.
Fault codes from Saunier Duval that this spare part resolves.
| Code | Fault | Diagnosis and solution |
|---|---|---|
| F.20 | Safety shutdown: temperature limiter. | If the 3-way valve (priority valve) is blocked or disconnected, the primary flow does not switch correctly and the generator overheats, triggering the F.20; to verify, force the test/diagnosis that moves the valve from the service menu and check the power supply/wiring and ensure the shaft/motor are not seized. |
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 the Saunier Duval 3-way valve S1025500.
- Catalogue reference
- S1025500
- Brand
- Saunier Duval
- Type of part
- 3-way valves
- Units in stock
- 1 unit
- Status
- Refurbished
- Warranty
- 1 year
- Shipping
- 1-2 business days
- Return
- 14 days
Manuals and technical documentation
Official documentation of the boiler, useful for locating the part and cross-referencing the fault codes.
- Saunier Duval F 35 E H-MOD Manual (PDF)Document © Saunier Duval, provided as a technical reference.
Frequently asked questions about the 3-way valve S1025500
Is this part the complete 3-way valve or just the motor?
Which Saunier Duval boilers is this 3-way valve motor compatible with?
How many boiler models are compatible with this motor?
What is the reference for this 3-way valve motor?
What fault code is documented for this product?
Spare parts related to Saunier Duval Isofast
