Breakdown guide
What to do first when heating, cooling or ventilation fails in a commercial building: keep people safe, carry out simple checks, and give the engineer the right information.
When commercial HVAC breaks down, make the area safe first, isolate leaking or smoking equipment only if it is safe to do so, and check simple things such as controller mode, setpoints and fault codes. Do not open panels or keep resetting tripped equipment. Then call an engineer with the site, equipment, symptoms and fault codes.
Likely causesController in wrong mode or setpoint, blocked filters, dirty or obstructed outdoor coils, failed fans, refrigerant leak, chiller or condenser fault.
Safe checksMode and setpoint, fault codes, filters (if accessible without tools), outdoor unit clear and fans running.
HVAC not cooling properly →Likely causesHeating plant off or locked out, valves or actuators stuck, heat pump defrost or flow faults, controls schedule wrong, failed fan in terminal units.
Safe checksTime schedule and setpoint, whether other zones are heating, heat pump or boiler fault displays, frost protection alarms.
Commercial heat pumps →Likely causesBlocked condensate drain, failed condensate pump, cracked drain tray, leaking valve or pipe joint, ice melt from a frozen coil.
Safe checksIsolate the unit if water is near electrics and it is safe to do so; protect stock and equipment; note which unit is leaking.
Fan coil unit problems →Likely causesBlocked filters, failed or slipping fan belts, closed dampers, fan speed set low, ventilation schedule off, blocked grilles.
Safe checksWhether the AHU or fan is running, filter alarms on the BMS, grilles obstructed by furniture or stock.
Commercial ventilation →Likely causesElectrical faults, failing motors or compressors, high-pressure trips from dirty condensers, low-flow trips, sensor faults.
Safe checksNote the alarm or fault code and when it trips. Do not keep resetting it.
Why HVAC keeps tripping →Likely causesWorn bearings, loose or damaged belts, unbalanced fans, loose panels, failing compressors, water hammer.
Safe checksWhich unit, when it happens, and whether it is getting worse. Switch off if there is grinding, burning smells or smoke.
HVAC repairs →One reset after checking for obvious hazards is reasonable on simple equipment. If it trips again, leave it off and call an engineer. Repeated resets can turn a minor fault into major damage.
Only where the filters are designed for user access without tools, the equipment is safely isolated, and staff are trained and permitted to do it. Otherwise leave filter changes to engineers.
There is no maximum workplace temperature in law. HSE guidance suggests a minimum of 16°C, or 13°C for strenuous work, and employers must keep temperatures reasonable. Assess the risk and take temporary measures if HVAC fails.
If there is fire, smoke or risk to life, call 999. For a suspected gas leak, call the National Gas Emergency Service on 0800 111 999. For urgent HVAC faults once people are safe, call our 24/7 contact line on 020 7998 9005.
Primary and industry sources relevant to this subject. Always check the current edition and how it applies to your building.
