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

HVAC Control in the New MillenniumDistributed TechnologyDistributed technology can be viewed as a group of control relateddevices and a common communication network. Building AutomationSystem (BAS) and Building Control System (BCS) are used interchangeably.Both of these terms refer to equipment that provides building-widecontrol, and integrates that control through distributed devices. Distributedcontrol devices rely on networking.Local Area Networks andDistributed ControlIn a Local Area Network (LAN) a node is any device on the networkincluding intelligent microprocessor-based controllers. A distributedcontrol system might control HVAC equipment and other loadssuch as lighting. Distributed control is applied at each piece of equipmentto provide an application specific control.Closed loop control is accomplished via the monitoring of statusconditions and execution of the required control actions. One architecturedefines four levels: sensor/actuator, distributed controller, buildingwidehost and central operator interface. Other architectures combinethe host and operator interface functions.A number of products have been introduced that use communicationnetworks, these are sometimes called sensor or field buses. Thistype of technology has been growing quickly.Remote SupportRemote support can take place through a modem interface overtelephone lines. This usually means that the remote interaction necessarybetween the central operating interface and the local system istransparent to the user at a remote site. One promising advance in thisarea is building-wide controllers that support plug-and-play. This featuresupports an object oriented concept, and stores all critical systeminformation at the controller level. Intelligent controllers of this typemake it possible to dial into a system from a remote location, uploadfrom the controllers and have full access to the system.©2001 by The Fairmont Press, Inc. All rights reserved.