A gas interlock refusing to open the solenoid valve is usually doing exactly what it was designed to do: withholding gas until ventilation and other safety conditions are proved. The correct response is to identify the failed input, not bypass the panel.
Safety first: Do not bridge the fan proof, gas proving, emergency-stop, detector or fire-alarm circuit, and do not manually hold the gas valve open. If there is a gas smell, alarm, failed proving test or unexplained pressure message, follow the emergency procedure and use competent Gas Safe and controls support.
Important: This is an operator-level diagnostic guide, not a repair instruction. Always follow the appliance manual. Gas work, live electrical testing, refrigerant work and access beyond user-serviceable parts must be carried out by people with the required competence and qualifications.
How the appliance and safety sequence work
A commercial kitchen interlock may require extract and supply fans to be switched on and proved before it energises the gas solenoid. More advanced panels also perform downstream gas-pressure proving and monitor low or high inlet pressure, emergency stops, fire alarm, fire suppression, carbon dioxide or carbon monoxide inputs.
Fan proof can come from differential pressure switches or current monitoring. Gas proving monitors whether the downstream pipework maintains pressure during a test sequence. The front-panel message is therefore a map of the system state: fan not proved, test failed, pressure outside limits or an external emergency input active.
What the symptoms suggest
| Observed symptom | What it may indicate |
|---|---|
| Panel dead | Control supply, fuse, isolator or upstream electrical fault. |
| Waiting for fans | Fan enable, airflow, pressure switch, current sensor or calibration issue. |
| Gas proving failed | Open appliance valve, downstream leak, pressure-sensor or proving-sequence problem. |
| Low or high gas pressure | Supply, regulator, pipe capacity, sensor or threshold issue. |
| Emergency or fire input active | Emergency stop, fire alarm, suppression or gas detector circuit has not reset or is genuinely in alarm. |
These observations narrow the investigation; they do not prove a component has failed. The same symptom can have an appliance cause, a utility problem or an installation cause.
Safe checks for kitchen staff
- Read the exact message: Photograph the full display and indicator sequence before pressing reset.
- Confirm both fans: Check extract and make-up-air switches and listen for operation. Do not assume a spinning motor proves designed airflow.
- Check authorised emergency resets: Inspect clearly labelled emergency-stop buttons for a pressed condition and follow the site's authorised reset procedure.
- Check fire and detection status: Do not reset or silence fire and gas detection equipment without the responsible person's approval.
- Turn appliance controls off before proving: Where the panel instructions require downstream appliance valves to be closed for a test, follow the exact operator sequence.
- Stop after a repeat failure: A proving or fan fault that returns needs competent diagnosis rather than repeated attempts.
Likely technical causes
| Area | How it creates the fault | Competent engineer's next step |
|---|---|---|
| Extract or supply fan not proved | The fan is off, airflow is low or the proof signal is missing. | Check fan duty, filters, belts, pressure tubes, switch thresholds or current calibration. |
| Gas pressure proving failure | Pressure falls during the test because an appliance control is open, there is leakage or the sensing system is faulty. | A Gas Safe engineer should check tightness, valve position and proving equipment. |
| Gas-supply pressure | Incoming pressure is below or above the panel's permitted band under operating conditions. | Check supply, regulator, pipework capacity and sensor calibration. |
| Solenoid valve | The panel output is present but the coil, valve, wiring or mechanical valve does not open. | Test electrical command, coil and valve, followed by the required gas-safety checks. |
| External safety input | Fire alarm, suppression, emergency stop, CO/CO₂ detector or BMS contact remains active. | Trace the input to the originating safety system; do not link it out. |
| Panel power or control fault | Fuse, transformer, wiring, relay or controller fails to complete the sequence. | Use the manufacturer diagram and retain all safety functions after repair and recommissioning. |
What not to do
- Do not bypass fan proving.
- Do not hold the solenoid valve open.
- Do not repeatedly reset a failed gas-pressure test.
- Do not change current or pressure thresholds without measuring and recommissioning the system.
Protective devices and lockouts are evidence. Bypassing them may temporarily hide the symptom while removing the control intended to prevent fire, shock, gas release, pressure, contamination or equipment damage.
Information to give the service engineer
- Panel manufacturer and model
- Exact screen message and indicator state
- Which extract and supply fans run
- Fan-proof method: pressure or current
- Gas-pressure message and whether appliances were off
- Emergency, fire-alarm and detector status
- Recent fan-speed, filter, gas or electrical work
- Commissioning values and previous fault history
A short video or photograph taken from the normal operating position can help, provided doing so does not delay emergency action or expose anyone to heat, gas, electricity, moving parts or chemicals.
Repair or replace?
Pressure switches, sensors, solenoid coils and panel components can often be repaired or replaced. A system upgrade may be justified where the panel is obsolete, no commissioning information exists, fan-proof method no longer reflects the ventilation design, multiple external interfaces have been improvised or wider kitchen changes require reassessment against current standards and manufacturer guidance.
Request a written diagnosis rather than a parts list alone. It should identify the failed function, the evidence, any upstream cause and the checks required before the appliance returns to service.
Preventing the fault returning
- Keep commissioning settings and wiring diagrams on site.
- Test fan proof and gas shutoff during planned maintenance.
- Maintain fans, filters, pressure tubes and sensing points.
- Record messages before resetting.
- Use Gas Safe and competent controls engineers with clear responsibility for the complete sequence.
Frequently asked questions
Why does the gas stay off when the extract fan is running?
The system may not be receiving its proof signal, airflow may be insufficient, the supply fan may be missing or another safety input may be active.
What does gas proving failed mean?
The panel did not see downstream pressure remain within its expected test condition. It may indicate an open appliance valve, leakage or a proving-system fault.
Can the interlock be bypassed for one service?
No. That removes a safety layer intended to prevent gas use without the required conditions.
Related Kitchen Install Guide reading
- Commercial kitchen gas interlock systems explained
- BS 6173 explained
- How to check a commercial catering gas engineer
Planning a repair, replacement or kitchen upgrade? Use the guide to understand how BS 6173 considerations, fan proof, gas capacity, ventilation and appliance installation fit together. KIG 317 commercial kitchen installation guide.
Sources and further reading
- HSE: Gas safety in catering and hospitality
- Medem: Commercial kitchen ventilation interlock and gas proving
- Medem VGPS installation instructions
- Gas Safe Register: Commercial catering
Technical information is general because control sequences and service procedures vary by manufacturer and model. Check the current manufacturer documentation and the requirements applying to your site.