Because You Know I’m All About That BAS

No, not that annoying song – I’m talking about that BAS – Building Automation System. The BAS, also known as a Building Management System (BMS), is a computer server/software networked with field devices that functions as the communication hub and nerve centre of a building’s mechanical systems. Building automation is a massive topic to be covering in a simple blog post, so I will keep it to a quick overview and show some advantages we have experienced at UHN with our various BAS configurations.Capture_2

At the centre of any BAS is a server and operator workstation, which communicates with various controllers, mechanical systems, and sensors (“field devices”) throughout the building or buildings. Typically, mechanical systems are represented on a user interface with graphics, such as the one above showing an air handling unit, that identify the systems and display current operation and control parameters that are available.

Communication between the workstation and the field devices uses one of many common communication protocols, such as BACnet, Modbus, LonWorks, etc. These protocols allow the central workstation to send commands to field devices and receive status information. A BAS offers numerous advantages over older, locally controlled systems.

Scheduling
The BAS offers a centralized location where all mechanical equipment can be scheduled based on the precise needs of the spaces served. For example, an auditorium may be commonly used during working hours and also used on weekends and evening on odd occasions. With local controls, would you schedule it to run 24 hours? Alternatively, you could put a timer on the equipment to run it during typical business hours, but you would still need to send an operator to modify the schedule every time an off hours event came up. With a central BAS, the operator can change the schedule with a couple of clicks and can typically log in from off site to make changes if necessary.  This flexibility allows the facility manager to be more aggressive when it comes to daily schedules.

Energy savings advantages
A BAS enables a facility to enjoy numerous energy savings advantages over a facility with only local pneumatic (compressed air powered) controls. Effective scheduling as described above allows unnecessary equipment to be shut down with much greater consistency. At UHN’s E.W. Bickle Centre, for example, during a review of the BAS through remote access, we identified several pieces of equipment that could be scheduled off during unoccupied times. This led to a quick savings of $7,700 per year on electricity.

A comprehensive BAS can also provide many energy efficient control options. The BAS typically includes one or more outdoor air temperature and humidity sensors, which can then be used to modulate temperatures in all other systems. For example, during heating season, if the outdoor air temperature is mild, the BAS can be programmed to automatically lower heating water temperatures to conserve energy. This type of operation is possible with legacy pneumatic controls, but it requires an analog outside air temperature input for each system (more equipment and more sources of error) and it is more susceptible to go out of calibration unnoticed.

Controls strategies such as averaging space heating/cooling demands to set the optimal air supply temperature simply are not possible with local controls. A BAS with room level thermostats and server computing power can take advantage of the information available from many spaces to supply the most efficient air temperature at the air handling unit level.

Maintenance advantages
There are numerous benefits that a central BAS can offer a facility manager. First and foremost, it can notify facilities staff of issues via alarms before they become a larger problem. For example, the BAS can email an alarm to a manager or operator if a boiler loop drops below a certain temperature. The staff can then look into the issue before temperature complaints come in.
Most modern BAS software also comes with the ability to trend/troubleshoot various parts of the mechanical system. A trend log simply tracks a given variable in the system over time and logs that information for easy viewing. This can be a valuable tool when troubleshooting problems. As an example, the graphic below shows the position of heating valve and the supply temperature of an air handling unit. As you can see, the valve is oscillating between 0 and 90% open every 5 minutes while the supply air is swinging wildly from 18C to 29C.

Capture

With a local pneumatic controller, you would never notice this type of problem unless you sat and looked at each piece of equipment for an extended period of time. In this case, the problem was identified on the BAS and rectified, leading to reduced wear on the valve/actuator and enhanced comfort in the spaces.

Further advantages to maintenance staff include displaying metering and sub-metering information and automated reporting.  Some building automation systems have advanced features that can incorporate security, fire systems, lighting systems, and more to make life easier for building operators.

Ongoing UHN Projects

UHN has several sites that have legacy pneumatic controls and we are currently working to upgrade these using pressure transducers to convert the analog pneumatic signals to digital signals that can be used by a BAS.  Expansions of the BAS at Toronto Rehab’s University Centre and Lyndhurst Centre are expected to yield savings of over $110,000 per year.

These are just a few of the reasons why I’m all about that BAS!

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