Building automation system design

A building automation system (BAS, sometimes called a building management system) monitors and controls heating, cooling, ventilation and other building systems, from the controllers on each piece of equipment to the operator's screen. We design BAS for new buildings, additions and controls upgrades, setting out the architecture, points, sequences, integration and security in documents a controls contractor can price, build and commission.

Many building automation problems trace back to the design stage. Specifications that say little more than "provide a complete BAS" leave each bidder to decide what that means. Sequences of operation are never written down, so nobody can tell whether the system is doing what it should. Closed, proprietary systems tie the owner to one service provider for decades. Alarms are so numerous that operators stop reading them. A clear design avoids all of these before the first controller is mounted.

What we design and build

• System architecture: servers, operator workstations, supervisory controllers, field controllers and the networks between them.
• Points lists for every piece of equipment, showing each input, output and value the system will read or command.
• Sequences of operation for air handlers, terminal units, boilers, chillers, pumps, exhaust and other equipment.
• Open protocols, usually BACnet, with Modbus or other gateways for equipment that needs them.
• Integration with lighting controls, metering, generators, access control and, for monitoring, the fire alarm system.
• Graphics, trends, alarms and reports that help operators run the building.
• Network design and cybersecurity for the BAS, coordinated with your IT group.
• Controls upgrades and migrations for existing buildings, including phasing so the building keeps running.

Most systems are organized in three levels. At the top, the management level holds the server, operator workstations and remote access. In the middle, supervisory controllers manage a plant room or a floor and connect to the building network. At the bottom, field controllers sit on each air handler, terminal unit or pump, reading sensors and driving valves, dampers and motors.

Integrating building systems

The BAS is often the one place where information from many building systems comes together. Some of those connections are two-way, where the BAS both reads status and sends commands. Others should be one-way only. The fire alarm system, in particular, controls its own life safety functions, such as fan shutdown and door release, through its own interfaces; the BAS may monitor it but must not be relied on for those functions.

How it works

1. We start with why. A new building, a failing or unsupported controls system, energy targets, comfort complaints or a move away from a single proprietary vendor each lead to a different scope. We ask who will operate the system, what they need to see and who will service it.
2. Site survey. For existing buildings we review the current controllers, networks, graphics and documentation, check how equipment actually runs against how it is supposed to, and identify what can be reused.
3. Design. We prepare the architecture, riser diagrams, points lists and written sequences of operation, working with the mechanical engineer so the controls match the equipment. We set the protocol, naming, alarm and trending requirements and the cybersecurity measures, agreed with your IT group.
4. Tender. The specification and points lists let controls contractors bid on the same scope. Drawings for permit are sealed by a licensed professional engineer where required, and electrical work is done by licensed electrical contractors under permit.
5. Construction and commissioning support. We review submittals and graphics, then witness or review point-to-point checks and functional tests of each sequence, so the system is shown to do what the sequences say.
6. Handover. We confirm that as-built documentation, controller backups, passwords and training have been delivered to the owner.

What to have ready

• Mechanical drawings and equipment schedules for the building or the area involved.
• Existing controls documentation, graphics and any service contracts.
• A list of comfort, energy or reliability problems you want solved.
• Your IT contact and any network or security policies that apply.

What you get

A BAS design that is written down: architecture and riser diagrams, a points list for every piece of equipment, sequences of operation in plain language, and a specification covering protocols, controllers, graphics, alarms, trends, network, security, testing and documentation. Because the system is specified around open protocols and owner-held documentation, you can choose who services it in the years ahead.

A typical case

An office building has a controls system from the 1990s that only one contractor can service, and replacement parts are getting hard to find. Tenants complain about hot and cold spots, and nobody can say what the air handlers are supposed to do at night. In a case like this, the design documents the existing equipment, writes sequences of operation for each system, and specifies a BACnet system installed floor by floor so the building stays occupied. Old controllers are replaced as each area is cut over, and the new system's trends quickly show which zones are fighting each other.

Who it's for

• Owners and developers of new commercial, institutional and multi-unit buildings.
• Facility managers with ageing or closed controls systems.
• Organizations working toward energy or emissions targets.
• Mechanical engineers and architects who need a controls specialist on the team.

For background, read our guides to building automation systems, BACnet and Modbus, BAS points and sequences of operation, cybersecurity for building automation and fire alarm interfaces with HVAC, doors and elevators.

Common questions