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    1. Smart Buildings

    ‘Work Smarter’ With Submeters

    April 30, 2003
    Proven Technology Shows How and Where to Cut Energy Costs
    Rising fuel costs have made energy resource management more important than ever before, but the kind of profiling needed by today’s building manager is simply not possible using the standard socket-based utility meter found at the main electrical service entrance. That’s why electric submeters have grown in use as first-level data-gathering tools that can literally save thousands of dollars in reduced energy costs, through: automatic meter reading (AMR) of electricity, water, gas, steam, and other energy sources; time of use monitoring of energy consumption patterns; multi-site and submetered load aggregation; usage analysis and identification of peak demand; and energy usage for cost allocation, tenant billing, and more.Submetering HardwareElectric submeters are installed after the facility master meter and are used to track the energy use of a specific location, user, or circuit. Installation of the preferred solid-state type submeter simply requires three split-core current sensors around the electrical feeds being measured in addition to the voltage input. The data is sent to the host computer from the meter via RS485 utilizing inexpensive 4-conductor phone cable. Communication wiring can be run up to 4,000 feet in total length. Data may be sent via modem or transmitted using standard RF technology. The submetered energy data is date/time stamped in five- or 15-minute intervals for up to 36 days. Recently introduced communications interfaces allow AMR hardware elements to operate with popular cellular services such as Sprint, Verizon, Voicestream, and other communications options. Once the data is collected on the host’s hard drive, it may be manipulated in software to produce itemized utility bills, generate load and usage profiles, customize spreadsheets, and create graphical charts and databases and other data analysis and reporting functions. LAN-based AMRThe pervasive use of local area networks (LAN) in campus environments, multi-facility commercial, industrial, and residential sites, creates new energy monitoring opportunities. Using the existing communications backbone eliminates the need for a modem and telephone line back to the central monitoring location, and allows a full-featured Ethernet-based distributed submetering network to be installed quickly and inexpensively. Hardware is available for star and bus topology Ethernet, as well as Fast Ethernet and fiber media, thus extending submetering’s usefulness to any Ethernet medium. Online Monitoring The Internet may now be used to track and analyze “big picture” electrical consumption (kWh) and demand (kW) – from a single circuit in one facility, to multiple sites around the world. The metered data is transmitted to a data accumulator or profiler and sent via modem to an online server operated by an RBC (read, bill, & collect) or other third-party energy monitoring service, which posts the data to the subscriber’s password-protected folder. The data may then be accessed using any standard Internet browser.Don Millstein is president at E-MON LP (www.emon.com), Langhorne, PA.

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