Building Management Systems,answered plainly.
Thirty of the questions we are asked most often by building owners, facilities managers, managing agents and M&E consultants, answered by engineers who work on these systems every week.
Understanding Building Management Systems
The questions we are asked most often by building owners, facilities managers and managing agents who have inherited a system somebody else installed.
What is a Building Management System?
A Building Management System (BMS), sometimes called a Building Automation System or BEMS, is the control layer that runs a building's mechanical and electrical plant. Controllers, sensors, actuators and a supervisor front end work together to operate heating, cooling, ventilation, hot water, pumps, air handling units, chillers, boilers and often lighting and metering. Instead of each item of plant running independently, the BMS sequences everything against occupancy, outside conditions and demand, then reports faults through alarms and trend data.
What is the difference between a BMS, a BEMS and a BAS?
In practice they describe the same thing. BMS (Building Management System) is the common UK term. BEMS adds 'Energy' to emphasise consumption monitoring and optimisation. BAS (Building Automation System) is the more common North American term. A modern BMS does all three jobs: control, monitoring and energy management.
What does a BMS actually control in a commercial building?
Typically air handling units, fan coil units and VAV boxes, boilers and chillers with their pumps and valves, heat pumps, hot water generation, pressurisation units, ventilation and extract, frost protection, and increasingly lighting, sub-metering and renewables. It also handles interlocks with fire and life safety systems, which are supervised rather than controlled by the BMS.
How do I know if my BMS is underperforming?
Common symptoms: recurring comfort complaints in the same zones, plant running outside occupied hours, alarms nobody actions because there are too many, overrides left permanently in place, no usable trend data, energy consumption that climbs without a change in occupancy, and a front end nobody on site is confident using. Any two of those together usually means the control strategy has drifted from how the building is really used.
What is a points schedule and why does it matter?
A points schedule lists every input and output the system monitors or controls: sensors, valve positions, status feedbacks, setpoints and alarms. It is the single most useful document in a BMS project, because it defines the scope, the panel sizing, the cabling and the software. A vague points schedule is the most common cause of a BMS project overrunning.
Our services and how we work
What BIAV Controls delivers, who does the work, and how projects run from first enquiry to handover.
What services does BIAV Controls provide?
Pre-design and specification, BMS installation, panel manufacturing to BS EN 61439, electrical installation via partner electricians, software and graphics, project delivery, planned maintenance, energy optimisation and 24/7 call-out. We work across the full lifecycle, so the same team that designs the strategy also supports it in service.
Do you work on systems you did not install?
Yes, and most of our service and optimisation work is on inherited systems. We are vendor-neutral and work on Tridium Niagara, Trend, Siemens (Desigo, Talon), Distech Controls, Cylon and Honeywell, plus any BACnet, Modbus, LonWorks or M-Bus device.
Are you tied to one BMS manufacturer?
No. We deliver on open protocols so you keep the freedom to change contractor or extend the system without replacing what is already installed. Where a client already has a platform standard, we work to it.
Who carries out the electrical work?
Certified partner electricians (NICEIC/NAPIT/ECA/ECS/CSCS) carry out electrical installation, with test certification issued on completion. Controls engineering, commissioning, software and graphics are delivered by our own engineers.
Where are your panels built?
Control panels are designed in-house and manufactured to BS EN 61439 by our panel-shop partner, then tested before delivery to site. We are honest about that split: the design and the strategy are ours, the fabrication is a specialist partner's.
Do you work on residential buildings?
Yes, mainly communal systems in apartment blocks and mixed-tenure developments: communal heating, heat networks, pump control, hot water and mechanical ventilation. We also attend high-end private residential systems.
Call-out, response times and maintenance
How fast we get to site, what a contract covers, and what happens when plant fails outside working hours.
Do you offer 24/7 BMS call-out?
Yes. Phones are answered 24 hours a day, Monday to Sunday, by a controls engineer rather than an answering service. Contract clients hold a 2-hour on-site response SLA. Non-contract callers are prioritised, typically within 24 hours depending on location and severity.
What is covered by a BMS maintenance contract?
Planned preventative maintenance visits on an agreed frequency, sensor calibration checks, actuator and valve inspection, panel and battery checks, software and database backups, alarm review, trend review, a written report after every visit, and reactive cover under an agreed SLA. Remote monitoring is included where the site supports secure remote access.
How often should a BMS be serviced?
Twice a year suits most commercial buildings, aligned to the heating and cooling seasons. Critical environments such as healthcare, data halls and laboratories usually justify quarterly visits. Buildings with heavy occupancy change benefit from more frequent setpoint and schedule reviews even when the hardware is healthy.
Can you monitor our system remotely?
Yes, where the site permits secure remote access. Remote monitoring lets us triage alarms, review trends and often resolve control issues without a site visit, which shortens downtime and reduces call-out cost.
What happens on a call-out visit?
We triage remotely first where access allows, attend site, isolate the fault, restore control by the fastest safe route, then issue a written report covering what failed, what was done, and any recommended permanent remedial work with a quotation where relevant.
Energy, efficiency and net zero
We are a family-run BMS specialist delivering smart, energy-efficient solutions to support net zero buildings. These are the questions that come up most around consumption and reporting.
Can a BMS actually reduce energy bills?
Yes, and usually without new plant. Most waste comes from setpoint drift, uncommissioned optimum start, time schedules that no longer match occupancy, uncalibrated sensors and simultaneous heating and cooling. Correcting those routinely takes 10 to 25 per cent off HVAC energy. On one of our site optimisation projects we identified £4,000 of monthly saving.
How do you prove a saving is real?
We establish a consumption baseline before works, then compare post-works consumption over a meaningful period, adjusted for weather and occupancy, and report the difference in kWh and pounds. Where a measure delivers less than expected, we say so.
What is simultaneous heating and cooling?
It is when a heating coil and a cooling coil work against each other on the same air stream, usually because a valve is passing, an actuator is mis-set or two control loops are fighting. The space feels fine, so nobody complains, while the building pays twice. It is one of the largest single savings available on an air handling unit.
Does a BMS help with ESG and net zero reporting?
Yes. Trend logs and sub-metering give you measured consumption by system, floor or tenant rather than estimates, which is what ESG frameworks expect. Reducing HVAC runtime is also the most direct operational carbon reduction available to an existing building.
Should I replace plant or optimise the controls first?
Optimise first, in almost every case. New boilers or chillers on a broken control strategy waste fuel just as efficiently as old ones. If replacement is genuinely the right answer once the controls are correct, we will tell you.
Projects, timescales and disruption
How installation and upgrade work is planned around a live, occupied building.
How long does a BMS installation take?
It depends on points count, access and whether the building is occupied. A single plantroom upgrade can be a week. A multi-floor commercial retrofit typically runs over several weeks to a few months, phased so each area is commissioned and handed back before the next begins.
Can you work out of hours to avoid disruption?
Yes. Cut-overs, panel changes and anything that interrupts heating, cooling or ventilation are normally scheduled at weekends or overnight, with permits, RAMS and access arrangements agreed in advance.
Can you upgrade a BMS in phases rather than all at once?
Yes, and it is usually the right approach in an occupied building. We integrate the existing system through open protocol gateways, then migrate floor by floor or plantroom by plantroom so the building never loses control of its plant.
What do we get at handover?
As-fitted drawings, updated points schedules, a controls narrative, commissioning records, panel test certificates, electrical certification, software and graphics backups, an O&M pack and on-site operator training so your team can actually use the front end.
Do you provide operator training?
Yes. Handover includes practical training on the supervisor: alarms, schedules, setpoints, overrides and trends. A front end nobody is confident using is a front end that gets bypassed.
Coverage, pricing and credentials
Where we work, what things cost, and the paperwork managing agents and consultants ask for.
What areas do you cover?
Swanley and the wider Kent belt (Dartford, Sevenoaks, Gravesend), the South East London boroughs (Bexley, Bromley, Sidcup, Orpington, Greenwich, Croydon), and Central London including the City of London and Canary Wharf.
How much does BMS work cost?
Quote on application. Pricing depends on points count, protocol, access, out-of-hours requirements and the condition of the existing system, so we scope after reviewing the site or specification and issue a written fixed scope before work starts. We do not quote blind.
What insurance do you carry?
£20M public liability, £10M employers' liability and £10M professional indemnity. Certificates are issued with RAMS ahead of mobilisation.
What standards do you work to?
Control panels are manufactured to BS EN 61439. Electrical installation is carried out by certified partner electricians (NICEIC/NAPIT/ECA/ECS/CSCS) with test certification. Installation and remedial workmanship carries a 1-year warranty.
Who is behind BIAV Controls?
BIAV Controls Limited (company number 16344714) is a family-run BMS specialist based in Swanley, Kent, founded by Bradley Thomas with over 13 years of hands-on controls experience across commercial, healthcare, education and residential buildings.
How do I get started?
Call 07782 247022 at any hour, email accounts@biav-controls.co.uk, or send the enquiry form on our contact page. Tell us the building, the platform if you know it, and whether it is a fault, a project or a maintenance requirement, and we will come back with a scoped response.
Question not answered here?
Tell us the building, the platform and the problem. You will get a straight answer from a controls engineer, not a sales script.