3-Way Valve Saunier Duval Isofast-Themafast Condens/NOx (Ref. S10255)
Three-way valve with a gray actuator. On its circular face, it has an embossed code, of which only the initial fragment 'UC103N0' can be reliably read; the rest is indistinguishable in the photos. It also has a white label on the arm, which is worn and has no legible text. The only confirmed identifying data on the piece is the code S10255. The manufacturer of the component is not specified.
Spare parts related to Saunier Duval Isofast
Saunier Duval boilers compatible with reference S10255
3-way valve with reference S10255. 28 confirmed compatibilities with two independent sources: Isofast Condens F 35 E and Isofast Condens F 30 E. Verify the printed reference on your part before purchasing.
Compatibility confirmed
| Boiler model | Family | Verification |
|---|---|---|
| Saunier Duval Isofast Condens F 35 E | Isofast | Confirmed · 2 sources |
| Saunier Duval Isofast Condens F 30 E | Isofast | Confirmed · 2 sources |
| Saunier Duval Isofast Condens F 35-A | Isofast | Confirmed · 2 sources |
| Saunier Duval Isofast 21 Condens F 25 | Isofast | Confirmed · 2 sources |
| Saunier Duval Isofast 21 Condens F 35-B | Isofast | Confirmed · 2 sources |
| Saunier Duval Isofast 21 Condens F 30-B | Isofast | Confirmed · 2 sources |
| Saunier Duval Isofast F 30 E H-MOD | Isofast | Confirmed · 2 sources |
| Saunier Duval Isofast F 35 E H-MOD | Isofast | Confirmed · 2 sources |
| Saunier Duval Isomax C 30 | Isomax | Confirmed · 2 sources |
| Saunier Duval Isomax Condens F 35 E | Isomax | Confirmed · 2 sources |
| Saunier Duval Isomax Condens F 35-B | Isomax | Confirmed · 2 sources |
| Saunier Duval Isomax F 35 H-MOD | Isomax | Confirmed · 2 sources |
| Saunier Duval Isotwin C 30 | Isotwin | Confirmed · 2 sources |
| Saunier Duval Isotwin Condens F 30-A | Isotwin | Confirmed · 2 sources |
| Saunier Duval Isotwin F 30 H-MOD | Isotwin | Confirmed · 2 sources |
| Saunier Duval Themafast C 25 E | Themafast | Confirmed · 2 sources |
| Saunier Duval Themafast C 30 E | Themafast | Confirmed · 2 sources |
| Saunier Duval Themafast F 25 E | Themafast | Confirmed · 2 sources |
| Saunier Duval Themafast F 30 E (2004) | Themafast | Confirmed · 2 sources |
| Saunier Duval Themafast F 25 E H-MOD | Themafast | Confirmed · 2 sources |
| Saunier Duval Themafast F 30 E H-MOD | Themafast | Confirmed · 2 sources |
| Saunier Duval Themafast NOx F 25-A LPG/GN | Themafast | Confirmed · 2 sources |
| Saunier Duval Themafast NOx F 30-NL/LL | Themafast | Confirmed · 2 sources |
| Saunier Duval Themafast Condens F 24 E | Themafast Condens | Confirmed · 2 sources |
| Saunier Duval Themafast Condens F 25 | Themafast Condens | Confirmed · 2 sources |
| Saunier Duval Themafast Condens F 30 E | Themafast Condens | Confirmed · 2 sources |
| Saunier Duval Themafast Condens F 30 (2010) | Themafast Condens | Confirmed · 2 sources |
| Saunier Duval Themafast Condens F 30 H-MOD | Themafast Condens | Confirmed · 2 sources |
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. S10255 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.
- Locate the reference printed on the body of the 3-way valve you have installed: it should indicate S10255.
- Check your boiler model on the nameplate and look for it in the list of compatible models on this page.
- Compare the connections and the body with the original part before installing.
- If you have any doubts, send us a photo of the screen printing via WhatsApp and we'll confirm it for you before you purchase.
Symptoms and faults resolved by the 3-way valve S10255
The 3-way valve diverts water between heating and domestic hot water. These are the typical symptoms and what to do:
The domestic hot water comes out intermittently, hot and then cold, without any apparent reason.
Cause: The valve actuator loses positioning accuracy and oscillates between the two circuits instead of staying fixed on domestic hot water.
Turn on the tap and observe the temperature for a full minute; if it fluctuates in waves, note the pattern before deciding to change the valve.
The heating takes a long time to start, or it seems like the boiler 'hesitates' before beginning to heat the radiators.
Cause: The motor of the valve takes longer to complete the turn towards the heating circuit, indicating wear in the gear.
Time how long it takes from when you request heating until hot water comes out of the nearest radiator; more than one or two minutes points to the valve.
A high-pitched beep or whistle is heard near the valve while the boiler is running.
Cause: A small water leak between the two circuits due to wear on the shutter generates that whistling sound when forcing the passage.
Locate the source of the noise with the boiler running; if it comes directly from the body of the valve and not from a pipe, it reinforces the suspicion.
The valve stem appears loose, bent, or the actuator feels loose to the touch.
Cause: An actuator that has fallen during a previous disassembly, or a stem forced by hand, may become misaligned without any visible signs.
Before installing the new one, check that the shaft of the old valve turns smoothly and straight; if it's bent, confirm that this is the cause of the fault.
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 3-way valve S10255
- OEM reference
- S10255
- 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
Data read on the part and in the manufacturer's documentation
What we have not been able to verify does not appear here.
- Part code
- S10255
label
- The actual manufacturer of the part is not listed on the label or the part.
- The code S10255 is the only confirmed identifying data; there are no further technical details established.
- The actuator has a partial code engraved, 'UC103N0...', which is not fully visible in the photos and has not been used to identify the manufacturer or cross-reference with external sources.
- The white label on the arm is deteriorated and does not provide readable information.
- This part is compatible with several models from the Condens range; check the exact model of your boiler before ordering.