Why does a design engineer need to worry about the controls network? For a long time, the cabling and network infrastructure of a building has been in the scope of the controls vendors, with each providing their own siloed system, from the physical device to the headend interface and everything in between. Many components of their software can be proprietary, only able to be accessed by the vendor that installed it, making it very difficult for different systems to communicate. 

They may be connected to a building network for remote access, which is convenient, but can also expose that network to cyberattacks since operational technology (OT) devices are rarely as secure as most information technology (IT) devices for which the network was designed. Thankfully, this status quo is changing quickly with advancements in controls technology catching on. 

Few engineers are keeping up with these changes, however, and are instead still leaving it up to the controls vendor to give the building owner a modern controls system. Engineers need to have information on controls networks so they can discuss options, needs and desires with the building owner during the design process, resulting in better-coordinated construction documents essential for them to deliver a final building of the future.

What is a Converged Network?

In the past, different types of controls used different types of infrastructure to communicate, making sense for them to operate in silos. Now that most systems are compatible with or use internet protocol (IP), it has become easier for them to share infrastructure. When multiple building systems such as the building management system (BMS) for HVAC, plumbing, lighting controls, energy management, access control and others, connect using share cabling and network equipment, it is called a converged network. 

Depending on how the building operator wants to manage it, this can be combined with the IT network or standalone as an OT network. Many components comprise the full building system stack, but it can be broken down into layers for easier understanding.

• Device layer. At the lowest layer are the physical controllers, sensors and other devices that operate the equipment, collect data or allow direct interaction with the systems. Examples include field controllers, thermostats, meters and occupancy sensors.

• Network layer. The next step up is the physical infrastructure, whether wired or wireless, allowing the device layer to communicate. All cabling that carries a signal is part of this layer, including analog, twisted pair and fiber. It also contains network equipment such as patch panels, switches, servers and wireless access points. 

In this simplified network layer model, communication protocols are also included with the network layer such as BACnet, DALI, Modbus and others. Standardizing and converging the network layer is a big step in preparing the building for the future.

• Data layer. Moving to the software side, the data layer stores all information produced by the system. Even if the network layer has been converged, having a converged data layer is rare today and most systems will operate their own data layer for operations. 

The way the data is processed, stored and accessed is inconsistent among different systems and vendors, with some providing live dashboards and historical trends while with others, an owner is lucky to receive Excel files on a regular basis. Updating specifications to require high data management standards will deliver a better product to owners, and working toward a fully integrated data layer will help create a truly intelligent building.

• Application layer. The software programs that run the building systems and are used to manage the facility are on this layer. Traditionally, the applications have been run on dedicated computers, but more and more have moved to web-based interfaces running on either cloud-based or on-premises servers. It is becoming common for different applications to integrate with each other using application programming interfaces. 

If an owner has requested functionality requiring two or more systems to work together, it is important to make sure those systems will be able to communicate. There has also been a rise in “single pane of glass” applications that integrate all building systems into a single interface.

Design Considerations

One of the most important decisions that needs to be made when planning a converged OT network is whether it will be combined with the IT network. A standalone OT network needs its own fiber backbone, network equipment, and, potentially, dedicated space in the building if not allowed in the data room. Extra costs are associated with this strategy, but the owner may want a contractor-provided OT network or have cybersecurity standards that do not allow OT devices on the IT network. Ideally, the direction for this gets decided before the end of the schematic design phase. 

Another impactful design consideration from an infrastructure perspective is establishing a wiring topology standard for the building. The three typical types are explained here, and the choice made will inform the order of magnitude of data connections that will be needed on the network layer.

• Daisy chain. Probably the most used topology in control networks today, a daisy chain is made of a string of devices, each connected to the one before and after it. One device is connected to the panel or switch to allow all devices on the chain to communicate with the larger network. While this is a highly efficient and easy way to coordinate topology, it has resiliency concerns since any one failed connection will impact every device further down the chain. Limiting the number of devices in each chain reduces risk.

• Ring. Similar to the daisy chain, the ring topology connects the first and last devices in the chain to the panel or switch. When the system can use rapid spanning tree protocol, information can flow in either direction on the loop, allowing communication to continue even if one of the connection points fails. A ring requires twice as many connections to the headend as a daisy chain containing the same number of devices.

• Star. In this topology, every device connects directly to the panel or switch. This is the most resilient topology and allows a high level of network management, but it also uses the most cabling and headend space by a large margin.

Any given project will likely use a combination of two or more of these topologies. For example, critical equipment may receive its own data drop, a star topology, while less critical components such as VAV boxes may be daisy-chained. Balancing cost and reliability based on the type of project and the owner’s preferences ensures that the headend and cabling infrastructure are sized appropriately.

The openness of a system will also have a big impact when the owner attempts to make changes or renew contracts. If a BMS only has one licensed vendor to perform maintenance in the area, the owner will have no choice but to pay its rates for service contracts. If they want to implement new software to perform fault detection, the onboarding process can be very time-consuming if the BMS does not offer easy access to the data. 

By specifying that systems are open, the building owner will have more freedom and control over the facility in the future.

Stakeholders 

Decisions made about controls during the design and construction of a project will impact many people, but those individuals are not usually solicited for input early enough in the process or given information to make informed decisions. Engineers can distinguish themselves with clients in the design process by understanding these different stakeholders and what needs to be coordinated with each of them.

• Network manager. Often referred to as IT, this is someone on the owner’s side responsible for managing the building’s network in operation. This person often knows very little about controls but will be the one allocating IP addresses and maintaining the network layer for the building systems, so coordinating with them in design will make things much smoother during construction. 

Cybersecurity is often one of a network manager’s biggest concerns, along with standardization of the network layer, so be sure to understand those requirements and incorporate them into the specifications. It is also important to establish what equipment they intend to provide and what will need to be provided by the controls vendors.

• Technology consultant. Often thought of as the “fourth utility” after mechanical, electrical and plumbing, technology consultants are being used to design all low-voltage systems and the IT network for many projects. They are sizing data rooms, specifying network racks and planning backbone and horizontal cabling. Establishing the architecture of the converged network with them helps ensure there will be enough capacity in data rooms to accommodate the OT systems.

• Master systems integrator (MSI). A new and evolving role in the industry, the MSI is typically responsible for coordinating different trades to integrate the network, data or application layers. They often respond to division 25 specifications, the integration section.

A well-planned, converged network lays the foundation for future scalability, operational efficiency and data-driven decision-making. However, it’s essential for design engineers to work closely with all relevant stakeholders to ensure the system meets the building’s unique requirements. This includes coordinating with IT teams, facility managers and system integrators to create a robust infrastructure that is secure and adaptable. 

By being proactive in the design phase and understanding the implications of network choices, engineers can help deliver smarter, more integrated building systems that are prepared to meet the evolving demands of technology and sustainability.

Will Maxwell, SmartScore AP, is a smart building consultant and project manager for Smith Seckman Reid, Nashville, Tenn. His multifaceted role encompasses the development, design and execution of smart building projects, along with guiding SSR’s standards and strategies for smart building design.