3-Way Valve Actuator Mechanism Sonceboz Saunier Duval Isofast Ref. 0020136956
The 3-way valve from Sonceboz for the Saunier Duval Isofast boiler switches the water between the heating circuit and the domestic hot water circuit. When it fails, you will notice that there is hot water, but no heating, or vice versa, or there may even be a mix of both circuits. This part is compatible with models such as Isofast F 35E, Isofast 21 F35, Isofast F 30E, among others. It is recommended to replace it when errors such as F.20, F.318, F.326, or F.081 appear, as they indicate problems in its operation.
VAT included
Consult via WhatsAppSaunier Duval boilers compatible with reference 0020136956
3-way valve with reference 0020136956. 19 verified compatibilities: Isofast F 35E and Isofast 21 F35.
Proven compatibility
| Boiler model | Family | Verification |
|---|---|---|
| Saunier Duval Isofast F 35E | Isofast | Contrasted |
| Saunier Duval Isofast 21 F35 | Isofast | Contrasted |
| Saunier Duval Isofast F 30E | Isofast | Contrasted |
| Saunier Duval Isotwin C 30 | Isotwin | Contrasted |
| Saunier Duval Isotwin F 30H | Isotwin | Contrasted |
| Saunier Duval Isomax F 35E | Isomax | Contrasted |
| Saunier Duval Isomax Condens F30 | Isomax | Contrasted |
| Saunier Duval Isomax Condens F35E | Isomax | Contrasted |
| Saunier Duval Themafast C 25E | Themafast | Contrasted |
| Saunier Duval Themafast C 30E | Themafast | Contrasted |
| Saunier Duval Themafast F25E | Themafast | Contrasted |
| Saunier Duval Themafast F30 | Themafast | Contrasted |
| Saunier Duval Thema F 24E | Thema | Contrasted |
| Saunier Duval Thema F 25E | Thema | Contrasted |
| Saunier Duval Condens F 24E | Condens | Contrasted |
| Saunier Duval Condens F 30E | Condens | Contrasted |
| Saunier Duval Semia F25 | Semia | Contrasted |
| Saunier Duval SemiaTek C 24 | Semia | Contrasted |
| Saunier Duval SemiaTek F 24 | 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. 0020136956 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 0020136956. 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 3-way valve 0020136956 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
You request hot water, but the boiler continues heating the radiators instead of prioritizing the tap.
Cause: The actuator has not switched the valve to the domestic hot water circuit even though the electronics have commanded it.
Listen to see if you hear the motor of the valve moving when you open the tap: if there's no sound, the actuator is not executing the command.
- 02
You notice that the radiators heat up a little when you only request domestic hot water, or vice versa.
Cause: The valve is stuck halfway between the two positions because the actuator does not complete the cycle.
Check if the actuator noise stops halfway through its stroke instead of completing the full rotation.
- 03
Lack of temperature or flow at the hot water tap even though the boiler ignites the burner.
Cause: If the valve does not fully switch, part of the water is diverted to heating, and power is lost in the domestic hot water circuit.
Check if the problem improves or worsens depending on whether the heating is on or off: if it depends on that, it points to the 3-way valve.
- 04
A buzzing or rattling noise is heard in the valve area when switching from heating to domestic hot water.
Cause: The internal gear of the actuator is worn out or forcing against a stop and does not rotate smoothly.
Check if the noise always occurs at the same moment during the service change: confirm that it is mechanical and not electrical.
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) gets stuck or disconnected, it does not divert the flow and causes overheating in the primary. Verify movement/position by performing an actuator test and checking the connector and continuity of the valve motor. |
| F.318 | The 3-way motor valve is not moving. | Mechanical/electrical fault of the 3-way mechanism prevents its movement. Check with actuator test, motor voltage, and condition of connectors/harness; replace if it does not operate. |
| F.326 | The hydraulic test of the sensor and actuator has detected that at least two hydraulic components are not functioning. | A blocked/disconnected 3-way valve causes the hydraulic self-test to fail. Check the operation of the 3-way motor with an actuator test, inspect the connector/harness, and replace if it is seized. |
| F.081 | The boost has failed. | If the 3-way valve does not prioritize DHW (blockage or defective motor), the boiler cannot perform the boost/preload. Check that when DHW is demanded, the valve switches to the PCB (actuator test) and that it receives power; replace if it does not change position. |
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 0020136956 three-way valve.
- Catalogue reference
- 0020136956
- 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
Frequently asked questions about the 3-way valve 0020136956
Who manufactures the actuator for the 3-way valve of the Saunier Duval Isofast?
Is this part the complete 3-way valve of the Isomax Condens or just the actuator?
When should the Sonceboz actuator Ref. 0020136956 be replaced?
Does this Sonceboz actuator work for a Saunier Duval Thema Condens F 24 E?
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