Gas Mechanism G20 Saunier Duval Isofast F28 E 1 Ref. 05742800
The Gas Mechanism G20 Saunier Duval Isofast F28 E 1 Ref. 05742800 is a gas valve that regulates and allows the flow of gas to the burner according to the instructions of the boiler's PCB. When this part fails, the boiler may not ignite, experience flame lockouts, or have modulation issues, which can lead to faults such as F.26 or F.28. It is compatible with several models from the Isofast, Isomax, and Isotwin ranges, such as the Isofast F 28 E1 and the Isomax C 28 E2, among others. It is recommended to replace it if these symptoms or associated faults are detected.
VAT included
Consult via WhatsAppSaunier Duval boilers compatible with reference 05742800
Gas valve with reference 05742800. 15 confirmed compatibilities: Isofast C 24 E V1 and Isofast C 28 E1.
Proven compatibility
| Boiler model | Family | Verification |
|---|---|---|
| Saunier Duval Isofast C 24 E V1 | Isofast | Contrasted |
| Saunier Duval Isofast C 28 E1 | Isofast | Contrasted |
| Saunier Duval Isofast C 28 E1 NOx | Isofast | Contrasted |
| Saunier Duval Isofast C 35 E1 | Isofast | Contrasted |
| Saunier Duval Isofast F 28 E1 | Isofast | Contrasted |
| Saunier Duval Isofast F 35 E1 | Isofast | Contrasted |
| Saunier Duval Isomax C 28 E2 | Isomax | Contrasted |
| Saunier Duval Isomax F 28 E2 | Isomax | Contrasted |
| Saunier Duval Isotwin C 24 E | Isotwin | Contrasted |
| Saunier Duval Isotwin C 24 EA | Isotwin | Contrasted |
| Saunier Duval Isotwin C 24 EV | Isotwin | Contrasted |
| Saunier Duval Isotwin C 24 EV A | Isotwin | Contrasted |
| Saunier Duval Isotwin F 24 E | Isotwin | Contrasted |
| Saunier Duval Isotwin F 24 E1 | Isotwin | Contrasted |
| Saunier Duval Isotwin F 24 EA | Isotwin | 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 the part number 05742800 is the one 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 05742800. 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 05742800 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 there is no sound of gas entering the burner.
Cause: The gas mechanism does not allow gas to flow to the burner even though the rest of the ignition sequence is completed.
Make sure that the gas valve of the boiler is fully open and that there is pressure in the supply line before replacing the part.
- 02
The boiler tries to ignite several times in a row and ends up locking out.
Cause: If the gas mechanism does not open consistently, the boiler retries ignition until it exhausts the attempts and locks out due to flame failure.
Count how many attempts it makes before locking and compare it with the normal in that boiler before ruling out other causes such as the ignition electrode.
- 03
It smells like gas when trying to ignite, although the boiler does not light up.
Cause: A mechanism that does not close properly can allow some gas to pass through without combustion occurring.
Shut off the main gas supply and ventilate; do not attempt to turn on the boiler until it has been checked with the gas supply cut off.
- 04
The boiler operates intermittently: sometimes it ignites and other times it does not.
Cause: A gas mechanism with internal wear may open irregularly instead of failing consistently.
Note under what conditions it fails (cold start, after a power cut, etc.) to rule out that it is an ignition problem and not a mechanism issue.
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 of the gas mechanism (valve ref. 05742800) is not operating or is disconnected. Check coil continuity and signal from the PCB; during demand, verify with a manometer that there is no pressure variation at the valve outlet. |
| F.27 | Safety shutdown: incorrect flame detection. | Non-sealed gas solenoid valve or one that does not close properly produces an incoherent flame signal. Check the valve's tightness (leaks) and ensure the flame extinguishes upon closing; replace the valve if it does not seal. |
| F.28 | Start-up fault: ignition failed. | The gas valve does not open or is misadjusted, preventing supply to the burner. Check that it receives command/voltage and coil continuity; measure inlet/outlet pressures during the ignition attempt. |
| F.61 | Gas valve activation fault. | Short circuit to ground in the harness or valve coils, or driver fault in the PCB prevents the valve from activating. Check insulation to ground, coil resistance, and control signal from the electronics. |
| F.62 | Gas valve fault: disconnection delay. | The valve closes late or does not seal (leaks), allowing gas to pass after the stop command. Check for the closing 'click', immediate drop in ionisation, and absence of gas/flame; perform a tightness test and replace if it does not close in time. |
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 05742800
- Catalogue reference
- 05742800
- Brand
- Saunier Duval
- Type of part
- Gas valves
- Units in stock
- 7 units
- Status
- Refurbished
- Warranty
- 1 year
- Shipping
- Delivery time shown at checkout
- 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.
- voltage
- 230V
- frequency
- 50Hz
- IP rating
- IPX4D
Frequently asked questions about the gas valve 05742800
Does this gas mechanism Ref. 05742800 work for a Saunier Duval Isofast F28 E1?
What fault does this gas mechanism of the Isofast F28 E1 solve?
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