Engineering in K-12 schools: Controls and automation
Engineers offer practical advice and best practices on how to design controls and automation systems in K-12 schools.
- Keith R. Hammelman, PE, Vice president, CannonDesign, Aurora, Ill.
- Robert V. Hedman, PE, LEED AP BD+C, Senior associate, Kohler Ronan LLC, Danbury, Conn.
- Pete Jefferson, PE, LEED AP, HBDP, Principal/vice president, M.E. Group, Overland Park, Kan.
- Essi Najafi, Principal, Global Engineering Solutions, Rockville, Md.
- Rodney V. Oathout, PE, CEM, LEED AP, Regional engineering leader/principal, DLR Group, Overland Park, Kan.
- Sunondo Roy, PE, LEED AP BD+C, Vice president, CCJM Engineers, Chicago, Il.
CSE: When designing integration monitoring and control systems, what factors do you consider?
Hedman: These systems must include monitoring points that will provide data useful in controlling, troubleshooting, trending, and education of system operation. Additional points that do not contribute useful system or educational information tax the project budget and increase system maintenance and complexity.
Najafi: The owner’s preference is an essential part of the control system approach. Some want a simple interface, leaving some operational aspects for manual operation, and others desire more sophistication, with integration into existing central reporting and, in some cases, a push toward an openness of control componentry, as with full BACnet interoperability.
Roy: Again, it goes back to knowing the technical sophistication of the client’s operating staff and designing the most efficient system within the complexity of controls the staff can manage. You can design a super-efficient system that requires highly skilled operators who understand complex control sequences and can adjust to varying conditions in equipment and climate conditions. Also, knowing the project budget is equally critical to avoid redesigning when estimates come in significantly over-budget.
CSE: What are some common problems you encounter when working on building automation systems?
Roy: For renovation projects, getting a handle on the capacity and capability of the existing controls systems. How many more control points can it handle without significant upgrades? What communication protocols can the existing system accommodate? How antiquated is the head-end hardware, and can it handle significant upgrades or does it need to be completely replaced?
Najafi: Closed proprietary systems are always a challenge in obtaining interface and programming support. The owner pays a high price for even minimal support effort. Another issue is keeping the software updated and the components current. Lack of proper maintenance and upgrade results in rapid system deterioration and poor performance.
Hedman: We often see equipment and system control problems resulting from incorrectly programmed sequences. These problems become evident when heating and cooling setpoints cannot be achieved. If commissioning is not performed, at a minimum a brief meeting with the control contractor is required for him or her to understand the intent of the design.
CSE: Please describe a recent project in which you integrated HVAC, lighting, and/or daylighting.
Hedman: Occupancy sensors with control outputs allow both lighting and HVAC systems to be interlocked. We have used these devices in classroom spaces to control both the operation of the lights and air supply to the room.
Najafi: Sophisticated lighting control systems are still a high-cost item, and connecting back to base building management systems, although doable, poses additional costs to the system. The District of Columbia Public School System (DCPS) is a big proponent of openness and interoperability when it comes to building management systems. We have recently designed a project for DCPS with a Lutron Quantum Total Light Management system, which consists of digital dimmable ballast, automatic dimming, and lighting control and daylight harvesting while integrating motorized shade controls. However, because of the high cost of the lighting system, the additional funding required in the budget to tie into the base building management systems was not available. To integrate both the lighting controls and HVAC, we were able to model the daylight harvesting and lighting controls into the energy model to realize some additional savings on the HVAC systems.
Roy: We typically integrate local HVAC VAV zone control of classrooms with the local lighting occupancy sensors to enable a setback condition when the room isn’t occupied, even during school hours. This would typically occur when students are out during lunch periods and recess. Combining with a cross-check of CO2 levels ensures that the class isn’t simply in presentation mode.