Tips and tricks for commissioning, balancing buildings: Electrical and power systems
Building commissioning is one of the most important (and complex) types of projects an engineer can be tasked with. Electrical engineering, power, and energy issues are discussed.
- 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’s the one commissioning issue most commonly overlooked in electrical/power systems?
Feyler: Most electrical design specifications require the contractor to perform a short circuit overcurrent protective device coordination study and arc fault analysis for the complete distribution system, including new (and existing) equipment from the service to the last panel board and overcurrent device. We have found that, in many cases, the study is not performed, or in most cases the study was submitted; however, the field setting of the breakers was not done and as equipment comes online, the breaker trips due to inrush or overload. This happens because the breakers were left at the factory default setting of minimum. Normally the contractor will adjust the setting to allow for the start-up; however, during the integrated testing phase of the project, as failure and loss of power scenarios are tested, in many occasions the building main breaker will begin to trip due to the setting not being implemented. We have added a coordination study verification task to our proposals.
Linder: Project specifications almost always require a power system study, consisting of short-circuit, coordination, and arc-flash studies. Unfortunately, the study provider is often selected based on price, not on qualifications. They commonly show little vested interest in the project. This often leads to poor study results and even worse implementation. As the CxA, we need to increase our involvement to ensure this effort is properly coordinated and executed.
Szel: One of the issues we commonly run into is the contractual responsibility for providing the testing equipment and load banks. These often get overlooked and are not budgeted for in the project budget. These can be performed by the CxAs or the electrical contractor, or a combination of both. The key is to ensure qualified manpower is available for installing and removing this equipment, especially in high-voltage gear.
York: Validating breaker settings is commonly overlooked in electrical systems. The designers routinely specify what the trip and time delay settings should be, but commonly the breakers are shipped from the manufacturers with the factory default settings. The installing contractors install these breakers and place them into service without ever adjusting them to the specified settings. The end result is someone plugs a faulty toaster into one receptacle and instead of tripping the small 20 amp breaker, the 800 amp main breaker trips and brings down the entire building feed.
CSE: How have energy efficiency and sustainability requirements affected your approach to commissioning electrical systems?
Wolff: We haven’t seen a significant impact related to energy efficiency or sustainability requirements other than with lighting systems. Type of lighting, light levels, and daylight harvesting have a direct impact on the occupied environment.
York: One is the emphasis we place on the lighting systems. Designers are now specifying lighting fixtures with lower energy consumption to satisfy the energy requirements. However, I commonly find fixtures installed that are not performing to specification—usually with regard to improper lighting levels. If left unchecked, the contractors just add more fixtures to bring the light levels into specification, thus eroding the energy savings produced with the low energy fixtures.
Szel: The majority of our larger projects are critical facilities where energy efficiency and sustainability tend to come second to uptime and reliability. When these clients want to incorporate these requirements, it is usually done at the design level by choosing and sizing equipment for peak efficiency.
Feyler: Energy efficiency and sustainability requirements have added to the commissioning process in the design and acceptance phases, lighting controls, daylighting and shade control, lighting power density (wsf), and efficiency of lighting fixtures, along with motor efficiency and control. During the design review, the reviewer needs to understand the owner’s project requirements and the designer’s basis of design along with standards or codes outlining the energy efficiency prerequisites. During the acceptance phase, the CxA will need to test the programming and functionality of the lighting control system. In complicated lighting control schemes, the lighting system can take a significant amount of time and due diligence as the building management system does.
Linder: It used to be that many owners believed that the electrical systems were good to go if they operated when the power was turned on. This is no longer the case. Owners understand the important role the electrical systems play in the efficient and continuous operation of their building. Owners are contracting electrical commissioning based on expertise and qualifications, not on price. This is the manner in which we want to contract for service. It is much more common to see utility metering, and multiple levels of submetering, on projects. Our customers are not just looking for LEED points; they are using the information for monitoring, maintenance, and optimization. These meters require additional effort be included in our scope of work to ensure the design, installation, and functionality meet the design intent.
CSE: If an owner is contemplating U.S. Green Building Council LEED certification or if ASHRAE 90.1-2010 compliance is required, the commissioning of lighting controls is a necessity. Describe a recent project in which you commissioned the lighting and related controls systems.
Feyler: The project was a multi-floor large open area renovation project that included a window wall on three sides of the open office. The lighting rows one and two, directly adjacent to the windows, were controlled by addressable ballasts via averaging daylight harvesting photocells. Lighting row 3 was also controlled via photocells on the interior of the space. The open office space was sectioned, with multiple occupancy sensors within each section; lighting was programmed to each senor via addressable ballasts. Occupied/unoccupied timing was controlled via a programmable time clock within the lighting control system, and night lights were programmed to specific occupancy sensors for after-hours egress. The lighting control system was connected to the BMS system via a modbus connection that enabled facilities to override the unoccupied time schedule. Interior closed offices were electrochromic windows on three sides, with occupancy sensors and bi-level switching. The open area window wall included an automated shading system that adjusted the shades throughout the day based on the sun’s position on each side of the building. The shades reduced glare and solar heat gain into the space, and the shade controller maximized the amount of available daylight entering the space. In addition to the shade control, cloudy day sensors were placed on the roof for each side of the building to override the shade controller, to allow the most amount of ambient light to enter the space on cloudy days.
York: I recently completed commissioning a museum project which used an advanced fully addressable daylighting control system with motorized shades. The roof consisted of hundreds of skylights with several photocells providing the main lighting controller information needed to make system adjustments. The motorized shades were controlled by a main controller which, knowing the time, date, and project location, raised and lowered the shades as appropriate to shade the incident light entering from glass walls. The largest challenge was timing and dampening the photocell inputs to prevent the system from adjusting light levels too frequently as clouds passed overhead.
Szel: We generally see lighting controls commissioning only on LEED projects. We are working on a volume LEED project currently and, in order to complete everything in one day, we begin with the lighting controls, light levels, and occupancy sensors at least an hour before dawn. This ensures we are the first ones in the building and can complete our testing before the sun is up.
Wolff: Commissioning of lighting and the associated controls happens on a most of our projects. Most facilities have some sort of lighting control system, ranging from simple occupancy sensors to the complex software control systems with multiple scenarios. In my experience the simpler systems usually cause us the most problems. For example, validating the operation of a simple occupancy sensor requires testing at least three things (time delay, coverage, and sensitivity). When you take into account most sensors have at least a 15-min, time delay, we are spending a lot of time validating a relatively inexpensive devise. However, we see a pretty high failure rate in our first round of testing.