Fault guide
Gas Interlock System Fault Diagnosis
Every gas interlock fault comes down to one of six things: power, emergency stop, ventilation proof, gas detection, the pressure proving test, or the solenoid valve itself. Working through them in order finds the fault quickly and safely.
- A structured fault route rather than guesswork and part swapping
- All makes covered: Merlin, S&S Northern, Medem, Flamefast, Intelligas, Duomo, Banico
- Repaired, tested and certified in one visit wherever stock allows
System architecture
The six fault categories
| Category | What you see | Where it leads |
|---|---|---|
| Power | Dead panel, no lamps | Fuse, isolator, transformer or failed panel |
| Emergency stop | E-stop lamp lit, no reset | A button pressed, damaged or wired loose |
| Ventilation proof | Fan fail lamp, trips on fan start | Air pressure switch, tubes, fan or make-up air |
| Gas detection | Alarm lamp or sounder | Sensor in alarm, drifted or end of life |
| Pressure proving | Lockout after the test period | Open appliance tap, leak or passing valve |
| Solenoid valve | Panel healthy but no gas | Coil, valve body or downstream isolation |
Safe checks before calling out
- Note every lamp, code and sounder state at the panel
- Release all emergency stop buttons, including hidden ones
- Confirm the extract fan is moving air, not just switched on
- Close every appliance tap and reconnect quick-release hoses
- Check the kitchen ventilation isolator and the panel supply are on
- Never bypass an input or hold a reset in to force gas through
If you can smell gas
- Turn off the gas at the emergency control valve and press the emergency stop button
- Do not switch anything electrical on or off, and do not use naked flames
- Open doors and windows, evacuate and keep people clear
- Call the National Gas Emergency Service on 0800 111 999
- Only then call us to make the installation safe and return it to service
Frequently asked questions
What is the most common gas interlock fault?
Airflow proving — a differential air pressure switch that has drifted, or sensing tubes blocked with grease. Emergency stops left pressed in are a close second.
Can the kitchen trade with an interlock fault?
Not on gas. If the interlock cannot prove ventilation, gas appliances must stay off until the fault is repaired.
Do you work on all brands?
Yes, including Merlin and S&S Northern CT1250/CT1650/CT1750, Medem, Flamefast, Intelligas, Duomo and Banico, plus generic and bespoke panels.
Will you certify the repair?
Yes, with a full interlock function test and documentation for your compliance file.
Related guides
Interlock Won't Reset
Reset sequence, latched faults and why the panel keeps dropping out.
Interlock Fan Fault
Fan fail lamps, airflow switch faults and extract failures.
Solenoid Valve Faults
Valve won't open, keeps closing, buzzing or leaking by.
Proving System Faults
Failed pressure proof, leak detected and reset lockouts.
Emergency Interlock Engineer
24/7 UK call-out when the kitchen has no gas and service is on.
Gas Interlock Systems
The pillar guide: how interlocks work, standards and fault-finding.
Parts in stock — ready to fit
Held in UK stock and carried on our vans, so most jobs are fixed in one visit.
Replacement gas interlock systems
Merlin, Medem, Intelligas, S&S Northern
In stock today
Air pressure switches
Fan & gas proving pressure switches
In stock today
Gas solenoid valves
Normally closed safety shut-off valves
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Quick release gas catering hoses
Commercial ranges, bays & mobile catering
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Super universal thermocouples
Fits most commercial gas appliances
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