Educational experience: Designing automation systems in K-12 schools
Engineering work on K-12 schools is complex—and not just because of dwindling school budgets. The facilities must meet a broad range of exacting standards coming from officials and state regulatory bodies, in addition to meeting energy efficiency standards. This discussion covers building automation and controls.
- Robert J. Linder, PE, LEED AP, Senior Project Manager, Karges-Faulconbridge Inc., St. Paul, Minn.
- Robert N. Roop, CPD, LEED AP, Principal, Peter Basso Associates, Inc., Troy, Mich.
- Abbas Shirian, PE, CGD, LEED AP, Principal-in-Charge, Lead Mechanical Engineer, Bridgers & Paxton Consulting Engineers, Albuquerque, N.M.
CSE: When designing integration monitoring and control systems, what factors do you consider?
Linder: We are finding that school districts are interested in moving away from proprietary control systems. The open architecture systems offer the flexibility to integrate multiple controls systems and select, or change, control vendors based on quality of service. This is especially true for larger districts that have multiple buildings using multiple control systems.
Shirian: Facility management systems (FMS) provide information to facilitate system operation but have the potential to overwhelm the operating staff with data of little value, thus obscuring important issues in the process. We focus on providing the facility staff with useful information to operate systems on a day-to-day basis and manage them over the life of the facility. The FMS must:
- Facilitate system operation and troubleshooting
- Make the building systems more energy efficient
- Be cost-effective (i.e., optimizing the use of packaged controls for air handling units vs. field-installed controls).
Roop: The biggest factor in application of any automation or control system is the level of user familiarity, aptitude, and desire to embrace the system. If the operators are familiar with a particular brand or system type, it is usually most beneficial for them to expand upon their knowledge and system base. When a strong preference or allegiance does not exist, we generally will highlight service and support from local vendors, and open system protocol type systems. Once a system type is selected, we will work to provide the owners with the level of control they desire, while maximizing energy saving opportunities. This is generally an educational process, since few owners have the broad spectrum knowledge of the industry and what is available that professionals do.
CSE: What are some common problems you encounter when working on building automation systems (BAS)?
Shirian: We struggle to get the BAS installed and programmed in accordance with our design intent. Commissioning helps greatly in this regard. We also regularly encounter challenges with client expectations regarding integration of different automation systems. Clients believe that when an existing automation system is integrated with a new one, either system should be completely accessible and controllable through the other. Unfortunately this is rarely the case.
Roop: Since many of our projects today involve some level of integration between manufacturers’ packaged controls and vendor-supplied building management systems (BMS), communication between the equipment manufacturer’s technical staff and the BMS vendor’s field staff is critical to the success of the project. In too many instances, operational issues result from communication gaps which lead to incorrect programming and/or wiring. These issues are often difficult to diagnose. A thorough commissioning plan involving functional testing of systems’ operation helps to minimize the lasting effects of this type of issues.
Linder: It is still common to find improperly operating, or even incomplete, controls work. Identified problems are typically related either to incomplete original construction or to poor operations. Some common findings include:
- Overridden schedules
- Uncalibrated critical control sensors, such as CO2
- Morning warm-up control sequences that provide ventilation (open outside air damper) when the intent is only to bring the space up to occupied temperature.
CSE: Describe a recent project in which you integrated HVAC, lighting, and/or daylighting.
Shirian: The most common use for the integration of the HVAC and lighting systems is to control the occupancy schedule of the HVAC system. On several projects we have linked the occupancy control of the HVAC to the lighting occupancy sensors. When the lights in an area are turned on by the motion sensors, the HVAC system for that area is switched from unoccupied mode to occupied mode. Once motion is no longer detected and the lights are turned off, the HVAC system is returned to an unoccupied state. This allows the HVAC system to operate less and at a lower capacity than using a standard occupancy schedule programmed into the building automation system. Our clients who have this integration have reported a decrease in energy consumption from reduced use of the HVAC system.
Roop: Nearly every project we do contains some measure of integration between the HVAC system controls and lighting controls. Occupancy sensors are used to switch lights off when rooms are unoccupied as part of the code requirement for automatic lighting controls, and we often use the same signal to put HVAC equipment into “stand-by” to save energy. The stand-by mode does not set back the room setpoint since the room may be unoccupied for a small period of time, but instead puts the room HVAC system into a recirculation mode, closing the outside air damper.