Gas Mechanism G20 Saunier Duval Isofast F28 E 1 Ref. 05742800
Refurbished Saunier Duval Gas valves

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. A technician must confirm through diagnosis whether it needs to be replaced if these symptoms or associated faults are detected.

Type of part
Gas valves
Status
Refurbished
Catalogue reference
05742800
Warranty
1 year
VAT included Stock · 7 units
Compatibility

Saunier Duval boilers compatible with reference 05742800

Gas valve with reference 05742800. 15 confirmed compatibilities: Isofast C 24 E V1 and Isofast C 28 E1.

Verified compatibility

Boiler modelFamilyVerification
Saunier Duval Isofast C 24 E V1IsofastVerified
Saunier Duval Isofast C 28 E1IsofastVerified
Saunier Duval Isofast C 28 E1 NOxIsofastVerified
Saunier Duval Isofast C 35 E1IsofastVerified
Saunier Duval Isofast F 28 E1IsofastVerified
Saunier Duval Isofast F 35 E1IsofastVerified
Saunier Duval Isomax C 28 E2IsomaxVerified
Saunier Duval Isomax F 28 E2IsomaxVerified
Saunier Duval Isotwin C 24 EIsotwinVerified
Saunier Duval Isotwin C 24 EAIsotwinVerified
Saunier Duval Isotwin C 24 EVIsotwinVerified
Saunier Duval Isotwin C 24 EV AIsotwinVerified
Saunier Duval Isotwin F 24 EIsotwinVerified
Saunier Duval Isotwin F 24 E1IsotwinVerified
Saunier Duval Isotwin F 24 EAIsotwinVerified

Can't see your model or have questions? The printed reference takes precedence. How to check it ·

Guide

How to check if the part number 05742800 is the one for your boiler

The part reference, model, and equipment revision must be verified against the manufacturer's documentation.

  1. 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.
  2. Check the full boiler model on its data plate and look for it in the model associations on this page.
  3. Compare the connections and physical body with the original part before installation.
  4. If anything is unclear, send us a photo of the marking via WhatsApp before placing your order.
Diagnosis and fault codes

Symptoms that require diagnosis in the gas valve 05742800

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 Saunier Duval that require diagnosis

CodeFaultTechnical checks
F.26Fault: 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.27Safety 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.28Start-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.61Gas 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.62Gas 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.

Technical data

Data sheet for the gas valve Saunier Duval 05742800

Catalogue reference
05742800
Uniclima internal SKU
VDGNIF28E1
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

Part data and available documentation

Contrast the label codes, PCB, and revision with the installed part; they are not necessarily equivalent references.

voltage
230V
frequency
50Hz
IP rating
IPX4D
Frequently asked questions

Frequently asked questions about the gas valve 05742800

Does this gas mechanism Ref. 05742800 work for a Saunier Duval Isofast F28 E1?
Yes, the Isofast F28 E1 is on the list of compatible boilers for this part.
What fault does this gas mechanism of the Isofast F28 E1 solve?
It should be checked when there is a failure in ignition or gas supply, as the mechanism regulates that flow to the burner. Replacement requires a technical diagnosis.

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Gas Mechanism G20 Saunier Duval Isofast F28 E 1 Ref. 05742800