3-Way Valve Saunier Duval Themafast (Ref. S1020900)
Three-way valve for Themafast and Themaplus boilers, in the indicated variants, according to the store's compatibility list. The part does not have a label or any additional legible markings in the available photos: the manufacturer and component code could not be identified, and there is no cross-reference with external sources. Confirm your part's reference before purchasing.
Spare parts related to Saunier Duval Themafast
Saunier Duval boilers compatible with reference S1020900
3-way valve with reference S1020900. Six confirmed compatibilities with two independent sources: Themafast C 24 E and Themafast C 24 E NOX. Verify the printed reference on your part before purchasing.
Compatibility confirmed
| Boiler model | Family | Verification |
|---|---|---|
| Saunier Duval Themafast C 24 E | Themafast | Confirmed · 2 sources |
| Saunier Duval Themafast C 24 E NOx | Themafast | Confirmed · 2 sources |
| Saunier Duval Themafast C 28 E | Themafast | Confirmed · 2 sources |
| Saunier Duval Themafast F 24 E | Themafast | Confirmed · 2 sources |
| Saunier Duval Themafast F 24 E NOx | Themafast | Confirmed · 2 sources |
| Saunier Duval Themafast F 30 E | Themafast | 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. S1020900 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 S1020900.
- 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 S1020900
The 3-way valve diverts water between heating and domestic hot water. These are the typical symptoms and what to do:
The radiators heat up when you only request hot water from the tap.
Cause: The three-way valve does not completely close the passage to heating and allows water to pass through both circuits simultaneously.
With the boiler cold, manually check if the valve shaft moves freely between the two positions or if it is seized.
The domestic hot water takes a long time to come out hot or comes out lukewarm.
Cause: The valve does not fully switch to the domestic hot water circuit and gets stuck halfway.
Listen to see if the valve motor makes the switching click when a tap is opened; if you don't hear it, the suspicion points here.
The heating is not warming up even though the boiler ignites and modulates well.
Cause: The valve gets stuck in the domestic hot water position and does not divert water to the heating circuit.
Check for leaks or drips around the valve body, a typical sign that the internal seat is no longer sealing.
A buzzing or knocking sound is heard in the area of the valve when switching between domestic hot water and heating.
Cause: The motor forces the position change because the internal mechanism resists.
Check that there is no lime or dirt blocking the stem's path before replacing the entire valve.
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 S1020900
- OEM reference
- S1020900
- 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
- The part does not have a label or legible marking in the available photos: the manufacturer and component code cannot be confirmed.
- There is no contrast with external sources for this piece (consultation quota exhausted during the review).
- The current catalog lists the reference S1020900 and the manufacturer Saunier Duval; this information is not verified in this sheet, compare with your removed part before purchasing.