Designing electrical systems for higher education
Electrical metering requests are becoming ubiquitous at university campuses, stemming from the need to monitor energy usage at individual buildings for billing purposes, LEED requirements, and additional sub-metering requests from individual university departments for energy studies or sub-billing. For buildings pursuing LEED certification, the process associates three credit points within the Energy and Atmosphere category, under Measurement and Verification. Electrical meters are required to monitor total building energy consumption, as well as submetering of various process categories, such as lighting loads, equipment, and plug loads.
A measurement and verification plan—even if not pursuing LEED—is a valuable tool in managing energy savings in a facility. These meters can provide information to continuously monitor the energy use of the facility and improve on the performance over the life of the building. Furthermore, they become an important tool in planning for future growth on campus. A university implementing a metering strategy will have average demand load data that can be analyzed per building type. These real data can be used to predict the energy usage of future installations and assist in planning for future expansion, and can be an invaluable tool for right-sizing equipment. Benchmark values derived from these data (Watts/sq ft) greatly assist the designers of future buildings.
A research building in a higher education campus will undergo a series of physical renovations during the life of the structure as the building has a substantially longer expected design life than many of its individual building components. The life expectancy of most electrical distribution equipment ranges from 35-40 years, indicating that several renovations will be required over the course of the 50- or 100-year building’s existence—and that building should be designed to facilitate the equipment replacements and upgrades accordingly (see Figure 6).
Incorporating this basis of design during the planning of the facility is paramount. To accomplish such a goal requires that electrical spaces are created with sufficient means for replacement of individual components with limited disruption to other operational equipment. Providing equipment removal paths as part of the design documents meets this purpose. For example, ensuring that a unit substation has enough room for its transformer to be removed, transporting via a clear path to an accessible exterior door sounds logical. But what if the unit substation is located at the lowest level of the facility, which happens to be below grade? Does the elevator have enough lifting capacity to handle the weight of a 2,500 kVA transformer core that weighs 20,000 lb? Such concerns play a major role in determining the replacement plan, not just for electrical elements but for all dynamic systems that will require reconfiguring during the life of the building (casework, laboratories, HVAC, and piping). The solution cannot be independent of other systems, as many opportunities arise by sharing equipment removal access among other trades.
Changeability also implies the ability for the facility to handle programmatic changes with prudent pre-investment. How can a university attract a researcher requesting high power into a building not planned for such high power research initially? Changeability features should be intuitive and transparent, meaning the facility owners must be aware of these elements. Prudent pre-investment may be allocating space for installation of future equipment, in lieu of procuring the equipment during the initial construction phase. For example, the main electrical service entrance room may include physical floor space for future substations, if a large electrical load is anticipated in the future, perhaps with monetary (grant) funding. Spare medium-voltage switches may be procured initially to serve this future equipment as a means of reducing facility downtime during the future renovation.
The 300,000-sq-ft Wisconsin Institutes for Discovery interdisciplinary research building on the University of Wisconsin campus in Madison was envisioned as a new direction in research facility design, flexible and sustainable (a 100-year building) while functionally demanding (see Figure 7). Among the various changeability features implemented at Discovery was to provide enough spare circuit breakers at the electrical panelboards initially to satisfy future space modifications. Adding an electrical circuit is ranked at the top of the service request when remodeling a space—at least a yearly event. A common design practice is to include 25% spare breakers in the initial design budget, 5% for changes that may occur during construction, and 20% for future modifications. Another implemented pre-investment was to provide stubbed-out empty conduits from the panelboard to the nearest accessible ceiling space. The quantity of spare conduits should provide capacity to handle the conductors needed to match the amount of spare breakers installed.
Other changeability features within a specific research lab or open classroom included the use of ceiling-mounted electrical devices. The concept of open spaces with ceiling-mounted utilities facilitates the future changeability of the space itself. Proper planning includes the standardization of receptacle types to be compatible with movable casework, as well as providing alternative voltages (i.e., 120 V, 208 V single- or 3-phase) at this space level. Another viable alternative is providing plug-in track busway where, for example, 120 V and 208 V, single- and 3-phase power can be derived with standard plug-in units via built-in drop cords.
As defined by IEEE, maintainability is "the ease with which a software system or component can be modified to correct faults, improve performance or other attributes, or adapt to a changed environment.” Maintenance is vital for the continuous and safe operation of higher education campuses. A well-planned electrical system will provide an up-front approach to maintainability by considering existing facility guidelines in conjunction with evolving codes and standards. Electrical working clearances (per National Electrical Code, Article 110) must be designed properly and maintained, taking into consideration that they are minimum code recommendations, and that they do not take into account the replacement means of the equipment. Standardization of components and in-stock spare parts can reduce downtime of operations considerably. For example, it is common for a draw-out switchgear design across a college campus to standardize circuit breaker frame sizes and maintain spares in stock that can be replaced among various facilities.
Equipment access remains a critical factor in maintaining a facility. During the design stage, consultants can facilitate this process with the BIM that has become a standard for sophisticated projects. BIM can visually present electrical systems in 3D software, and can include the equipment code clearances and access space as part of the illustrations. This tool proves invaluable in providing an avenue to ensure that the maintainability of the systems can be achieved. For example, cable tray access can be modeled—not just with the physical dimensions of the tray itself, but with the recommended continuous access space above of 12 in. and 24 in. on at least one side.
One must not forget about the experience that the building’s facilities and service personnel bring to the equation. Site standards, preferred vendors (offering familiarity and standardization), safety protocols (preferred arc flash categories and infrared scanning), lessons learned, and operational requirements are parts of a successful maintainability goal that these groups of individuals must ultimately execute. Managing these requirements can be quite challenging, as the initial capital investment must balance the pre-investment of future maintenance costs.
Providing today’s higher education clients with a reliable, flexible power infrastructure based on prudent first cost investments, managed with energy monitoring and optimized maintainability, and capable of supporting 100-year buildings is the unique challenge for the design professional delivering an electrical system. The extent to which the client’s expectations are met and all these elements of the campus are realized will be fundamental to the future success of the institution.
Cordero is a senior electrical engineer with Affiliated Engineers Inc. in Madison, Wis. He specializes in complex higher education, health care, and research facilities. His most recent school projects are the Wisconsin Institutes for Discovery at the University of Wisconsin (2012 Lab of the Year) and the Eckhardt Research Center at the University of Chicago.