LANs Provide Inexpensive Submetering for Data Highways

Although the technology has been around for several years, some contractors are just now experiencing a surge in submeter sales. "It appears as though in this last year I've had more and more requests for [submeter] jobs," said Dan August, a technical division manager at Mona Electric in Clinton, Md. "The attention deregulation is getting in the press has made more people aware that they need to be planning ahead. People on the tip of energy use know they need to get a grip on monitoring their consumption to reap energy savings," August added. As big a part as deregulation will continue to play in energy savings, it isn't the only market force driving increased submeter sales. For example, school construction spending is expected to top $17 billion this year, with 50 cents of every dollar going to new construction, 28 cents to modernization and 22 cents for additions. The "1999 School Construction Report," issued by School Planning and Management magazine, reveals that over 75 percent of the nation's elementary schools and some 90 percent of middle schools already have some form of local area network (LAN). Most colleges and universities do, too. The extensive use of LANs in school and campus environments, and also in multifacility commercial, industrial, and residential sites, is good news for building managers, electrical personnel, and maintenance engineers challenged with cutting operating costs. It's also good news for distributors who sell submeters to the contractors who install them. Mostly, as it turns out, this work comes in retrofit situations. Mona Electric's August says, "Most of the jobs I've handled recently come from a customer request and me making submetering a need." Submetering hardware Submeters are used to define the energy usage of a specific location, user, or circuit. They are installed after the master meter in a building or facility. The data obtained through submeters can be used to implement demand-side energy management programs, identify load shedding and other cost-cutting measures that can really impact the facility's bottom line. In those roles, they are relatively inexpensive and very well suited. In facilities that are not already wired for LANs, the submeter data must be carried back to the central monitoring point via home cabling runs. However, in a high percentage of applications, having the data highway already in place makes installing the distributed submeter network much faster and a lot less expensive. LAN-based automatic meter reading's (AMR's) popularity increases With more than 80 percent of the worldwide installed base, Ethernet is the LAN technology of choice. Its popularity is due mainly to its low cost and industry-wide support. Using a facility's existing LAN backbone as the submeter data highway can dramatically reduce submetering installation costs because this eliminates cable runs between hardware elements and also the need for a modem and telephone line back to the central monitoring location. Submetering hardware is now available for star- and bus-topology Ethernet, particularly 10Base-T and 10Base-2. (See Figure 1.) Inexpensive switches and interfaces are also available for Fast Ethernet and fiber media, thus extending submetering's usefulness to whichever Ethernet medium may be encountered. Figure 2 shows a typical Ethernet star topology network. Note that not only electric but also gas, water, steam, BTU, and other pulse output meters can be read on the network. This allows facility personnel to view total energy usage, not just electricity. The data accumulator hardware interface between the submeter network elements and the LAN provides an RJ-45 connection that may be hooked into the LAN wherever a connection can be found. The data accumulator records energy profiles with a date and time stamp every 15 minutes for rolling periods of up to 36 days. Battery-backed memory protects the data in the event of a power outage, and it can be stored in the accumulator for later retrieval or uploaded to a central monitoring location at any node on the network. On-line monitoring capability In recent years, Internet services have opened to help users track and analyze their "big-picture" electrical consumption and demand: from a single circuit in one facility to multiple sites all over the world. The metered data is transmitted to the data accumulator hardware interface and then sent via modem to the on-line server. The information is posted daily to the subscriber's password-protected folder, where it may be accessed using standard Internet browsers. Graphical and statistical presentations of peak demand load profiles and energy usage help users identify energy-saving opportunities and areas where efficiency can be improved. Multisite and aggregated load profiles enhance the user's ability to proactively negotiate the best possible rates in the deregulated utility marketplace. Typical monitoring functions include the ability to: * Track facility energy use of electricity, water, natural gas, oil, and steam. * Obtain seven-day energy, weather and/or degree-day forecasts. * Profile detailed hourly and daily load shapes. * Offer monthly and/or year-to-date budget status. * Set budgetary and energy-usage level alarms. * Determine length of use and time of use. Conclusion For many contractors and distributors, submetering is already a money-maker. Meters are easy to install and can be mounted anywhere, which means very profitable installations are possible in about 25 percent of the time it would take for the utility to come out and put a dedicated, socket-based meter on the same circuit. Recently introduced Ethernet-compatible submetering equipment makes it even easier and less expensive than ever to implement a distributed submetering network where a LAN is already in place. It also speeds up an already rapid system payback by increasing the utility and value of the LAN and by making critical information more easily accessible from any point on the information superhighway. In the new information age, the opportunity is also the challenge. Contractors who understand power and low-voltage communications are in a position to profit greatly. Firms are learning to install data communications networks. With all the new construction and retrofits going on everywhere, most involving LANs of some type, this kind of differentiation just could swing the vote your way in a tight, competitive-bid situation. MILLSTEIN is president of E-MON Corp of Langhorne, Pa. He can be reached at (800) 334-3666 or by e-mail at

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