Building Control Systems

Building control systems here means the controls layer — the building management system with its sensors, controllers and field devices — rather than the local authority's building control department. It is the part of an installation that decides when plant runs, how hard it runs, and in response to what. Boilers, chillers, air handling units and fan coils are mostly obedient; they do what the controls tell them. Which is why a building with well-specified plant and neglected controls usually performs worse than an ordinary building with a strategy somebody has thought through.

Wasted energy tends to come down to a small set of recurring faults. Plant runs to a schedule written for an occupancy pattern that changed years ago. Control valves pass because actuators have failed in a mid position. Points sit in hand on a manual override applied during a call-out and never reversed, and a sensor reading somewhere unrepresentative quietly drags a whole zone with it. None of these register as breakdowns, so nobody reports them — the building simply uses more energy than it needs to and nobody can say why.

Scheduling is usually the first thing worth fixing. That means occupancy profiles per zone rather than one building-wide time clock, optimum start so the building reaches temperature by opening time instead of at four in the morning, optimum stop so it coasts on residual heat, and overnight setback rather than a hard off that forces a brutal morning recovery. Frost protection and holiday calendars are set explicitly. Where hot water is stored, the strategy must respect the temperature regime required for legionella control under ACOP L8.

A control system is only ever as good as what it measures. A sensor sited above a radiator, in direct sun or beside a doorway produces a comfortable-looking trend and an uncomfortable room. Return-air sensing in a fan coil reports mixed air rather than the occupied space. CO₂ sensors let ventilation modulate with real occupancy instead of running flat out for an empty meeting room, but they drift and need periodic calibration to stay honest. Zoning should follow how the building is used and where solar gain lands through the day.

Interlocks are the safety-critical half of controls and are treated as such. Air handling plant must shut down or change mode on a fire alarm signal, and dampers need end switches that prove position rather than assume movement. Commercial kitchens require a gas safety interlock under BS 6173 so the supply cannot stay live when the fans are not proving airflow. Frost coils, flow switches, drive run and fault signals and pump duty-standby changeover all belong in a documented strategy rather than in one person's memory.

Where controls are tired, recommissioning what already exists is usually the better first move: schedules corrected, sensors calibrated, overrides cleared, alarm priorities set, and the strategy written down so the next engineer inherits something. Where a genuine upgrade is warranted it can normally be phased, replacing the head end and controllers while retaining field devices that still work, so a site in Newbury, Thatcham or the wider West Berkshire area is not shut down for a rip-and-replace. Remote connections are configured to your IT policy rather than to whatever is quickest.