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

Computer Networks and SecurityThe mixing of open system standard protocol capabilities withproprietary system functionality leads to increased costs and createspotential purchasing and implementation problems.Detailed functions and services must be specified since many standardprotocols do not provide the same capabilities. These includemonitoring, alarm, setpoint changes and scheduling functions.The definition of system integration responsibilities is importantwhen using equipment from different manufacturers. These responsibilitiesinclude integrating new equipment and the database at the operatorworkstations to incorporate new requirements. Changes in onemanufacturer’s hardware or software may affect other portions of thesystem.The definition of factory and field testing is also important. Thisincludes the acceptance criteria, based on individual component andintegrated system functionality. This functionality must be tested at bothlevels. It is not enough to test the monitoring and control functionssupported by the open systems protocol from the workstation to eachfield panel. The programming functions required at each field panellocation must also be tested.Maintenance is a critical issue for the successful operation of thesystem. System maintenance refers to both hardware and software.Hardware maintenance is simplified because of built-in equipment diagnosticsand plug-in replacement boards. Software maintenance can bemore demanding since there may be multiple databases and applicationprograms to maintain as well as several different programming languages.Electrical and mechanical system maintenance programs can beused for preventive maintenance and trend recordkeeping.System HardwareSoftware is only part of the solution, the hardware on which thesoftware runs is also important. The PC system can be an industrialcomputer, commercial-grade computer, or open type of controller. Thehardware usually depends on the environment in which it will run.Industrial computers are available with shock-mounted hard drives, ballbearing and filter cooling fans, internal temperature sensors, redundanthard drives, system control monitor cards and uninterruptible powersources.©2001 by The Fairmont Press, Inc. All rights reserved.