Tips and tricks for commissioning, balancing buildings: Building automation
Building commissioning is one of the most important (and complex) types of projects an engineer can be tasked with. Building automation systems (BAS) and sequence of operations are covered in this Q&A.
- Jerry Bauers, National director of commissioning, Sebesta Blomberg, Kansas City, Mo.
- Michael P. Feyler, Co-director, building solutions group, RDK Engineers, Andover, Mass.
- Robert J. Linder, PE, Senior project manager, Karges-Faulconbridge Inc., St. Paul, Minn.
- James Szel, Senior vice president, Syska Hennessy Group, New York City
- Geremy Wolff, Commissioning manager, McKinstry, Bellingham, Wash.
- Barney York, Project manager, RMF Engineering, Baltimore
CSE: What factors do you need to take into account when commissioning and integrating automation and controls systems?
Feyler: The sequences of operation are developed by the design engineer and oftentimes with packaged controls, the seamless integration of what is carried through to the BAS for operational control of the unit and what is controlled by the packaged unit itself, is often challenging to test to ensure the system is operating to meet the design intent. During the scheduling of the testing phase, it is important to have the manufacturer’s rep or HVAC contractor who is familiar with the packaged unit’s integration to the BAS on hand to be able test those sequences.
Bauers: Commissioning control systems requires that we thoroughly understand both the sequence of control that is intended by the designer and the energy objectives of the project. With most control system commissioning efforts, we find that the sequences are often underspecified and unclear. Further, the sequences may be inconsistent with both the installed equipment and the desired energy profiles. Finally, especially in critical environments, coordinating these two essential design criteria must also be validated against the mission critical performance characteristics required to achieve mission support and, where required, regulatory compliance.
Szel: Understanding how the client intends to use the control system is the first step. Some clients have 24x7 support to directly monitor their system. Other clients are off-site and expect the system to be entirely independent, able to be remotely monitored (and sometimes controlled) and annunciate any issues out to the first responders. As a CxA, having a solid understanding of how the systems interface, in conjunction with the client’s needs, creates a quality solution. It is also important for the sequences of operation to be approved by the engineer of record early in the project. Quite often, sequences are revised very late in the project, which can delay the final turnover date.
York: The biggest factor is determining exactly how the owner intends to use each area of their building. Oftentimes the owner has a highly technical expectation of its building that a designer attempts to meet with a very standard, no-frills, non-expandable control system. Commissioning often provides value by first ensuring the proposed control system is the proper match for the owner’s present and future needs.
Linder: We take the time to understand how the building operations staff is going to use the automation system. Are they going to actively use the system to operate, maintain, and optimize their building, or are they going to use it only for monitoring? Additionally, what are the future plans? This knowledge is critical to ensure the system is set up properly for the staff.
Wolff: The brand of controls, complexity of the system, and the skill set of the controls technician who will be performing the work. These will typically impact how much time is spent to successfully commissioning the system.
CSE: What aspect of the building automation system (BAS) is most overlooked when initially designed? What solutions have you offered clients when commissioning the BAS?
York: A significant number of design firms do not have design engineers that fully understand BAS. As a result, the mentality is that the BAS contractor will “make it work.” When this occurs, drawings and specifications lack the technical detail required to transfer the owner’s project requirements to the systems within the building. Unless the CxA for the project reviewing the project documents is knowledgeable in the design and functionality of the BAS, owners can be left at the mercy of the BAS contractor for numerous costly change orders and project schedule delays. We have assisted clients with developing project requirements they can present to the design team before design begins for a project. When reviewing the project documents, we are already quite familiar with the design standards and are able to provide comments that ensure the documents are matching the client’s requirements for the project. We have also assisted clients by having the BAS contractor demonstrate its programming for the project in a simulator prior to downloading the programming into BAS controllers on-site. This allows “bugs” to be worked out in advance, minimizing start-up and schedule delays.
Bauers: The two most often underspecified items in control systems are the sequences of control and the alarming and reporting strategies to be implemented by the control vendor. With regard to sequences, we will also spend a disproportionate effort in understanding and clarifying the sequence of control to make its translation into control code as seamless as possible. We also work closely with the operating teams and the designer to define the graphics interface and an effective alarming and reporting strategy for the completed system. We replace the time honored control vendor tradition of working these things out with the operators at the end of the job.
Feyler: What is often overlooked is the skill-set of the building facility personnel that is left behind when the project team leaves. In some cases, the BAS if often over-sophisticated for the type of building it is operating, and the training is often not long enough to ensure a successful turnover. We offer the client additional system education via having the facility team join the CxA during the testing of the systems to observe how the system operates and how the BAS interacts with each system. In most cases, training put into a specification is classroom-style training and not field training or hands-on training that RDK offers during the testing phase and warranty phases of the project. In addition, trending reporting should be included in the specification that would allow a continuous commissioning of the building. This is not always the case; the CxA will always request trending reports prior to the testing of the systems.
Linder: Owner preferences are commonly overlooked by the design team. Simple things like a fan status can end up being a thorn in the side of the building operator. Do you use a current switch, a pressure sensor, or a status command? These are all acceptable methods, but which is preferred? Communicate with your owner and don’t overlook the details. A controls shop drawing review meeting is a great way to cover these details. We invite the controls contractor, engineer, and the owner’s operations staff to a meeting where we dissect the controls shop drawing. All decisions are made at this meeting and the controls contractor leaves with an approved shop drawing to start their work. Everyone understands the decisions that were made, and why they were made.
Wolff: Integration of the BAS to the package controls or other systems. The team needs to fully understand what is needed from the integration (control, monitoring, alarming, trending, etc.) and what limitations exist.
Szel: Again, how the client intends to use the final configuration of the BAS is the most overlooked aspect. The initial design is usually good, choosing the points and describing the sequences of operation, but doesn’t always take into account how the client is going to use its system. Getting the BAS contractor and the owner (or facility engineers who will be operating the building) into the same room early in the process helps the client get what it needs in the system without the contractor having to redesign a system at the end of the project when there is almost always a time crunch. Another overlooked aspect is often the integration between multiple control systems, such as multiple BAS systems. To provide optimum efficiency in operating the facility, it is important for there to integration between control systems, so the operating team does not have multiple consoles, etc., to operate.
CSE: Describe a sequence of operations challenge you solved in a building automation/control system.
Szel: As CxAs we do not write the sequences of operations, but we have encountered actual field-programmed sequences of operation that are more detailed or slightly different from the published sequences of operation. At that point we advise the owner, engineer of record, and the Cx team of those differences; allow the owner and engineer of record to decide the best solution; and work to revise the Cx functional test scripts accordingly.
Wolff: This happens every day. One of the most common is how to control pressure within a building. The sequence to operate systems with combination return/relief fans and dedicated exhaust dampers is one we typically provide significant input on. One of the most common challenges we face related to sequences of operation is that often the designers and controls technicians focus on each individual piece of equipment and lose sight of the overall function of the building as a whole. Through our process of looking at the building holistically, we can easily identify where an action of one system will strongly affect the actions or performance of another system. This is often overlooked in the implementation of the sequence.
Bauers: In the process of commissioning containment laboratories, we are tasked with complying with National Institutes of Health/U.S. Centers for Disease Control and Prevention standards for pressurization of laboratories. In these standards, laboratories must remain under a negative pressure at all times, including through transient failure conditions. Working closely with the operations team and the control contractor at a Texas university, we were able to use the stack effect of the exhaust system to eliminate transient pressure reversals that are inherent to systems that respond to supply or exhaust failures with fully closed dampers. While the concept is novel, the success of our efforts was driven by our patient adjustment of control loop tuning and the timing of control responses to failures.
York: A science building had an issue with its laboratory exhaust fan system that consisted of three fans. When an additional fan was called to operate, the fan that was coming online would begin to freewheel backwards as soon as the isolation damper for the fan was fully open. Once the damper fully opened, an end-switch was made and the fan would attempt to turn in the correct direction. The fan could not overcome the backwards momentum and, as a result, the fan’s associated variable frequency drive (VFD) would trip on an overcurrent situation. We recommended adding a time-delay relay in series with the end-switch safety circuit and starting the fan at minimum speed prior to opening the isolation damper. As a result, the fan was able to start in the correct direction prior to the isolation damper opening. Once the time-delay relay contact dropped out, the end-switch was made on the damper, keeping the safety circuit intact. Another project had a static pressure reset sequence for an air-handling unit (AHU) and associated terminal units based on terminal unit damper positions. We discovered that often a terminal unit with a mechanical or damper actuator issue would drive the AHU static pressure setpoint to the maximum value, thus wasting energy. We recommended additional programming that would identify terminal units responsible for this issue, temporarily remove them from the sequence, and send an alarm to alert the appropriate personnel to investigate the issue. As a result of the energy savings achieved from this change, the owner elected to implement the same change in other buildings on its campus as well.
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