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

Advanced HVAC Control, Information Technology and Open Systemstion ports and software drivers. These gateways and drivers are relativelyexpensive. All features are provided in the drivers and must beupdated when one of the manufacturer’s products changes.Since the manufacturers of building automation systems approachedtheir products and features differently, these proprietary systemshad strengths and weaknesses that made them more appropriateand competitive for specific applications.End-users preferred the products they had experienced, becausethey have been trained to make these products work. The costs of trainingfor multiple systems, spare parts maintenance, along with employeeturnover, cause multiple-system applications to be less desirable.Users desire a standard method that ensures unrelated productscan communicate with each other under a competitive bid structure.One problem is that systems already installed will not easily or completelybecome compatible without gateways, software drivers, or replacement.Buildings often have existing computer networks that can beused as a communication medium for the building automation system.ProtocolsThe Building Automation Controls Network (BACnet) protocolwas developed by ASHRAE. BACnet is a multi-layer Open System Interconnection(OSI) basic reference model. It is a set of rules that allowsunrelated manufacturers to communicate in predefined data packets.The GSA has made BACnet a requirement in their buildings. Early concernsabout large data packet transfers under BACnet have been provenunwarranted.Another protocol is the Local Operators Network (LonTalk) whichwas developed by Echelon and implemented on an integrated circuitcalled the neuron chip. In the chip are three microprocessors. Two areused for networking and one for application-specific tasks in controldevices.Open Control DevicesThermocouples are one type of control device. Biodata’s TC15-Lonis designed to monitor temperatures. Providing 15 channels, it connectsto a LonWorks network using 4-wire telephone cable which carries both©2001 by The Fairmont Press, Inc. All rights reserved.