In short
A BMS fault needs urgent attention when it stops heating, ventilation, cooling or water systems from running, prevents plant from being controlled, or hides alarms on critical equipment. Before calling, record the alarm list, which plant is affected and any recent changes. Do not override safety interlocks. An engineer can then investigate the controller, network, sensors and outputs.
Is it urgent?
Call now if
- Heating, ventilation or cooling will not start because of a controls fault
- The BMS has lost communication with plant and alarms are not being seen
- Plant is running uncontrolled or overheating because of a control failure
- Critical alarms on boilers, pumps, pressurisation or server-room cooling
Usually suitable for scheduled work
- Nuisance alarms that clear and do not affect plant operation
- Schedule or setpoint changes for comfort or energy
- Graphics, trend logging and reporting improvements
Critical BMS alarms
A building management system watches plant and raises alarms. In an emergency, the alarm list is the best evidence you have. Photograph it before anyone acknowledges or resets alarms.
Common urgent controls faults
| Fault | What you may see |
|---|---|
| HVAC control failure | Plant does not respond to commands, runs in manual or stays off |
| Plant sequencing fault | Boilers or pumps do not start, or standby does not take over |
| Heating schedule not operating | Building cold at start of day, no call for heat |
| Failed control signals | Valves or dampers stuck, fans not ramping |
| Temperature control problems | Overheating or underheating across zones |
| Actuator faults | Valves or dampers not moving to commanded position |
| Sensor failures | Readings stuck, out of range or missing |
| Communication issues | Controllers offline, graphics frozen, alarms not reaching operators |
Equipment alarm history
Alarm and trend history shows the order in which things failed. An engineer can use it to tell whether a controls fault caused a plant failure, or the other way round.
Safe actions before the engineer arrives
- record alarms, controller screens and affected plant
- note any recent changes: software updates, power cuts, maintenance or new equipment
- check whether local hand or auto switches have been left in the wrong position
- do not override safety interlocks such as frost, fire, flue or pressure protection
Manual operation has risks. Running plant in hand without interlocks can damage equipment or create unsafe conditions. Only authorised, trained people should do it, and only where the controls design allows.
Professional fault investigation
The engineer checks controller health and power, network communication, inputs from sensors, outputs to valves, fans and pumps, and the control strategy. Where a full fix takes longer, they can often restore safe operation of critical plant first.
Scope of this page
This page covers urgent faults that stop mechanical systems operating. Detailed BMS installation, upgrades and maintenance are covered on Flair’s BMS services. For non-controls faults, see plant room repairs and HVAC repairs.
BMS & Controls Faults: frequently asked questions
When does a BMS alarm require urgent engineering attention?
When it relates to plant that has stopped or is unsafe (boiler lockouts, pump failures, low system pressure, high temperatures in critical rooms), when the building has lost heating, ventilation or cooling, or when the BMS has lost communication and can no longer show alarms. Nuisance or informational alarms can usually wait.
The heating schedule did not start this morning. What should we check?
Check the BMS time schedule, holiday calendar and any manual overrides, confirm the outside air or frost settings, and see whether the controller is online. Record what you find. Do not force plant on by bypassing interlocks.
What is a plant sequencing fault?
Sequencing decides which boilers, chillers or pumps run and in what order. If sequencing fails, plant may not start, may run all at once, or may not change over to standby equipment.
Can a failed sensor stop the heating?
Yes. A failed outside air, flow or space temperature sensor can make the controls think heat is not needed, or trigger protective shutdowns. Sensor faults are a common, quick-to-fix cause of plant failures.
Do you install and maintain complete BMS systems?
This website covers urgent controls faults affecting building operation. For BMS design, installation and planned maintenance, Flair Facilities Ltd provides BMS services through its main website.
UK guidance and references
Primary and industry sources relevant to this subject. Always check the current edition and how it applies to your building.
- Workplace temperatures Health and Safety Executive
- Ventilation in the workplace Health and Safety Executive
- Electrical safety at work Health and Safety Executive