HVAC Control in the New Millennium.pdf - HVAC.Amickracing

Energy and Power Management, Distributed Control TrendsLegal RamificationsThe legal area continues to grow. Many activities that were conductedeasily without problems now require careful justification anddocumentation. The trend is towards more detailed recordkeeping tohelp a company prove its case if needed at a later date. Building ownersas well as manufacturers have seen an increase in litigation, in areassuch as indoor air quality.Improving quality and holding down costs is proving to be a difficultchallenge for those in charge of operating a building. Buildingefficiency requires capital investment. When money is limited, operationsand maintenance functions can fall out of the bottom of capitalfunding requests. These cost-avoidance projects are often passed up formore lucrative, but possibly riskier, direct revenue-producing projects.Since departments must compete among themselves to receive themoney they need, better documentation of operations is needed.Energy Management and NetworksNetworked control systems started during the energy crises of the1970s, when the rising prices of imported oil triggered severe restrictionson energy use and prompted more efficient energy management andcontrol. This resulted in the development of energy management systems(EMS) for tightly monitoring energy usage. These systems grewover the years in both sophistication and scope.One offshoot appeared in the 1980s called building automationsystems (BAS). These systems added historical data, trend logging andfire and security functions to traditional energy management functions.These applications focus a return on investment based on utility savings.Analog and Digital SystemsThe advent of direct digital control systems in the mid-1980s displacedolder analog closed-loop control (Figure 2-1) as the temperaturecontrol scheme of choice for most large equipment. The digital systemsimproved both accuracy and reliability. But, these systems were modeledafter existing system architectures that did not include intelligent,©2001 by The Fairmont Press, Inc. All rights reserved.