Saunier Duval Gas Valve Isofast Condens 21 F30-B Ref. VK8515M 4504
The gas valve Saunier Duval Isofast Condens 21 F30-B 4504 regulates and allows the flow of gas to the burner according to the instructions of the control board. When it fails, the boiler may not ignite, experience flame lockouts, or have modulation issues. Users may notice faults such as F.26, F.61, F.62, F.27, or F.28. This valve is compatible with models such as Semia Tek F 24, Isotwin C 30 E, and Isomax C 30, among others. It should be replaced when faults in the gas supply or ignition are detected.
VAT included
Consult via WhatsAppSaunier Duval boilers compatible with reference 0020124874
Gas valve with reference 0020124874. 11 verified compatibilities: Semia Tek F 24 and Semia Tek C 24.
Proven compatibility
| Boiler model | Family | Verification |
|---|---|---|
| Saunier Duval Semia Tek F 24 | Semia / Semia Tek | Contrasted |
| Saunier Duval Semia Tek C 24 | Semia / Semia Tek | Contrasted |
| Saunier Duval Semia F 24 | Semia / Semia Tek | Contrasted |
| Saunier Duval Semia C 24 | Semia / Semia Tek | Contrasted |
| Saunier Duval Isotwin C 25 E | Isotwin | Contrasted |
| Saunier Duval Isotwin C 30 E | Isotwin | Contrasted |
| Saunier Duval Isotwin F 25 E | Isotwin | Contrasted |
| Saunier Duval Isotwin F 30 E | Isotwin | Contrasted |
| Saunier Duval Isotwin F 30 H | Isotwin | Contrasted |
| Saunier Duval Isomax C 30 | Isomax | Contrasted |
| Saunier Duval Isomax F 35 H | Isomax | 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. 0020124874 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 0020124874. 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 gas valve 0020124874 resolves.
The gas valve regulates and modulates the gas flow to the burner. These are the typical symptoms and what to do:
Common symptoms and faults
- 01
The boiler does not ignite and locks out without a flame appearing.
Cause: The gas valve does not allow gas to pass to the burner at the moment of ignition, so the spark has nothing to ignite.
Check that the main gas valve is open and that there is no air left in the system after a supply interruption before considering the gas valve faulty.
- 02
The gas flow is irregular: the flame varies in intensity without any change in heat demand.
Cause: A fault in the internal regulation mechanism of the gas valve causes the gas flow to not remain constant.
Measure the inlet gas pressure with a manometer during operation; an unstable pressure in the network produces the same effect.
- 03
There is a noticeable gas leak in the gas valve itself or its connections.
Cause: The internal seal or the sealing gaskets of the valve can deteriorate over years of use.
Locate the exact point of the leak with soapy water before replacing the entire valve; sometimes it's enough to tighten or change a connection gasket.
- 04
The boiler stops during operation and needs to be reset to turn on again.
Cause: A valve that loses tightness or does not maintain the flow rate can cause the flame to go out and trigger the safety lockout.
Note if the cut coincides with the peak demand for domestic hot water or heating; it helps to determine if the issue is with the gas flow before replacing the gas valve.
Fault codes from Saunier Duval that this spare part resolves.
| Code | Fault | Diagnosis and solution |
|---|---|---|
| F.26 | Fault: gas valve not functioning. | The stepper motor/actuator of the valve is not connected or the valve assembly is faulty, so it does not open/close. Check by measuring the signal to the modulator, continuity/insulation of coils, and power supply from the PCB. |
| F.61 | Fault: control/activation of the gas valve. | Short circuit to ground in the harness towards the valve or coils in short prevent its activation. Check coil resistance, leaks to ground, and continuity/wiring between the PCB and valve. |
| F.62 | Gas valve fault: disconnection delay/not sealed. | The valve does not close in time or does not seal (leaks), leaving gas when it should not. Check tightness and closing times; soap/manometer test and control signal without the presence of a flame. |
| F.27 | Safety shutdown: incorrect flame detection (flame simulation). | The sealed gas solenoid valve allows gas to pass when it shouldn't, simulating a flame. Verify with a tightness test and ensure there is no opening signal with ionization reading present. |
| F.28 | Start-up fault: ignition failed. | Incorrect/faulty or improperly regulated gas valve prevents gas supply to the burner. Check pressure before/after the valve, correct type, and signal/modulation; adjust or replace the valve. |
| F1 | Ignition fault (lockout). | In Semia/Semia Tek ranges, the gas valve that does not open or is improperly adjusted prevents ignition. Check the supply and ensure the valve opens (manometer on test point, voltage/signal to the actuator) and adjust/replace. |
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 gas valve Saunier Duval 0020124874
- Catalogue reference
- 0020124874
- Brand
- Saunier Duval
- Type of part
- Gas 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.
- component code
- VK8515M 4504
- secondary internal reference
- 0020 043 184 -1
- code on separate golden label
- 106 MOU005
Manuals and technical documentation
Official documentation of the boiler, useful for locating the part and cross-referencing the fault codes.
- Saunier Duval Isotwin C 30 E Manual (PDF)Document © Saunier Duval, provided as a technical reference.
Frequently asked questions about the gas valve 0020124874
What code is engraved on the gas valve of the Isofast Condens 21 F30-B?
Is this valve suitable for the Saunier Duval Isomax C 30?
What other internal reference appears on the label of the gas valve of the Isofast Condens F30?
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