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

HVAC Control in the New Millenniumoutside temperature sensor for hot water reset, which signals a boilercontroller to produce hot water at the correct temperature to satisfy abuilding’s heating load. The use of installed equipment from multiplevendors can be expensive to interface and the installation of controlequipment from another manufacturer requires new skills.As products improve, the life cycle for these systems is becomingshorter. Parts and service for older systems can cause costly delays andit may become more economical to install newer systems that can providemore efficient performance along with modular design for easiermaintenance.A proprietary control system usually requires proprietary hardwarefrom the original manufacturer. The move to interface computercontrol systems from different manufacturers is driving the growth ofopen systems for commercial and industrial control.The open system notion allows the connection of control systemcomponents from different manufacturers to operate as an integratedsystem in a mode which is transparent to the user. The system componentsalso become more competitive with improved availability.The open systems concept has been demonstrated in IBM personalcomputer systems. These computers are based on open specificationsand any manufacturer can build systems around them. This results insystem interoperability in a more wide open market.Open System IssuesAs open systems come into widespread use, several issues need tobe evaluated. The protocol functions supported need to include readingdigital and analog values, changing setpoints and schedules, and downloadingdata.Operator workstation functionality may be limited when communicatingwith the open protocol equipment. Ideally, conformance withinteroperability should be plug-and-play.The functionality of the operator workstations are important sincesystem configuration, routine engineering and maintenance functionsare not usually performed at a single location.Several trade-offs are involved in using open systems. These includeperformance limitations, system integration, maintenance, andservice issues.©2001 by The Fairmont Press, Inc. All rights reserved.