Quick answer
When commercial HVAC breaks down, follow five steps. Protect people and equipment. Work out what the building has lost and where. Record alarms and fault codes before anything is reset. Decide whether it is urgent or can be scheduled. Then call an engineer with the site, equipment, symptoms and access details. Never open panels, keep resetting tripped plant or work on refrigerant circuits.
The checklist
- Protect people. Move occupants from unsafe conditions; keep people away from leaks and electrics.
- Protect equipment. Cover or move IT and stock under leaks; consider portable cooling for critical rooms if available and safe.
- Identify what is lost. Ventilation, heating, cooling or all three? Which floors and zones?
- Record before resetting. Photograph BMS alarms and local controller screens.
- Check the obvious safely. Time schedules, setpoints, hand/auto switches, fire alarm status.
- Decide urgency. Use the table below.
- Call with details. Postcode, equipment, symptoms, alarms, access, on-site contact.
- Keep a log. Times, actions, resets, who was contacted.
Urgent or scheduled?
| Situation | Priority |
|---|---|
| Ventilation lost in occupied areas or kitchens | Urgent |
| Server or comms room cooling lost | Urgent |
| Central AHU or chiller stopped, will not restart | Urgent |
| Water leaking from HVAC equipment | Urgent if near electrics or spreading |
| Single fan coil or room too warm or cold | Usually scheduled |
| Noise or filter alarm, plant still running | Usually scheduled |
Common reasons plant stops
Frost protection, fire alarm interlocks, airflow or filter alarms, motor overloads, failed belts, power loss and control faults. Knowing which alarm appeared first helps separate safety shutdowns from failures.
What not to do
- open electrical panels or unit casings
- repeatedly reset plant that trips
- override frost, fire or pressure interlocks
- touch refrigerant pipework or attempt to recharge systems
After the breakdown
Ask for the cause in writing and review whether maintenance covered the failed equipment. See emergency HVAC repairs and the plant room emergency checklist.
Frequently asked questions
Is a ventilation failure always urgent?
Loss of ventilation to occupied spaces, kitchens or plant areas should be treated promptly because employers must provide adequate ventilation. Failures in unoccupied areas may be scheduled.
What if the HVAC stopped after a fire alarm?
Many systems shut down on fire alarm signals by design. Plant should only be restarted once the fire alarm has been investigated and reset by the responsible person.
UK guidance and references
Primary and industry sources relevant to this subject. Always check the current edition and how it applies to your building.
- Ventilation in the workplace Health and Safety Executive
- Workplace temperatures Health and Safety Executive
- F gas in refrigeration and air conditioning GOV.UK
This guide is general information for commercial building operators. It does not replace an assessment by a competent engineer. If you smell gas or a CO alarm sounds, leave the area and call 0800 111 999; if there is a risk to life, call 999.