SPECIAL FEATURES This month: Building control design process and intelligent HVAC systems BUILDING CONTROLS THAT WORK Building controls systems are complex and can be a major obstacle to good performance if they are not specified and commissioned properly. Building Intelligence Groups Paul Ehrlich says new tools and standards are helping to digitise the design process and streamline verification M any HVAC system designers find that building automation and controls can be one of the most frustrating parts of a project. Often, there may be a lastminute push to get the details for the specifications, points list, sequences and diagrams completed before the project can go out to tender, and that means working with limited time, and without enough hours to put much effort into the design. Working with the control contractor can be a challenge as well from prices that exceed the budgeted amount to problems with the products, design and performance. After the project is complete, the owner may complain that the controls dont seem to work in the way they expected. It seems like there has to be a better way to design and deliver controls. The processes of designing, installing, programming, commissioning and operating control systems are complicated and fraught with problems. These range from a lack of training, to keeping up with new technology, and the complex process required to interpret design documents and deliver control systems. In many ways, we are fortunate to have projects that work as well as they do. Is there a better way? The challenges with the design and delivery of control systems are long-standing. Changes in codes and standards, and the need to have systems that provide improved energy efficiency and a healthy indoor environment, further exasperate these challenges. Fortunately, these problems have not gone unnoticed. In the United States, efforts are now under way from ASHRAE and the US Department of Energy to improve the process and practice of controls design, delivery and documentation. Several of these programmes were highlighted in papers delivered at the joint virtual CIBSE ASHRAE Technical Symposium 2020, held in October. PAPER E S LECTED Technicalm Symposiu osium .org/symp www.cibse 2020 ASHRAE Guideline 36 One of the most important efforts is coming from an ASHRAE committee, which has produced guidance based on research of the bestpractice HVAC control systems. This project is titled High-performance sequences for HVAC systems.1 Guideline 36 defines best practices for efficient operation. A properly developed sequence can give significant efficiency improvements. The initial release, in 2018, focused on common airside systems, including single- and multiple-zone variable air volume (VAV). Current work is focused on expanding the guidance to include boiler and chiller plants. Over time, the effort will cover even more system types. The guidance provides a detailed sequence for each system type, as well as copious notes for the designer. It accompanies ASHRAE Guideline 13, which focuses on how to write a controls specification. Open building control The US Department of Energy-funded Open Building Control project is intended to improve the process of controls design and delivery by developing tools and standards that will digitise the process beginning with design through installation and verification. The idea is to start with new tools for the system designer that allow them to select from a library of high-performance control sequences including those in Guideline 36 or to develop their own sequences. Sequences are developed using a graphical format in a control description language (CDL). The use of CDL allows for sequences to be tested during design and to be used as part of an energy simulation. Testing during design helps minimise the need to make changes during 28 December 2020 www.cibsejournal.com CIBSE Dec20 pp28-29 Control program v2.indd 28 20/11/2020 15:04