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

HVAC Control in the New Millenniumclasses means that the goals of the project become important in writingBACnet specifications. There is an effort to make BACnet easier tospecify and to simplify the BACnet specification process. The committeecharged with the maintenance of the BACnet standard (ASHRAE SSPC-135) has been redefining how to specify BACnet.The BACnet standard has detailed information on how to implementthe protocol. Clause 22 is devoted to the specification of BACnetsystems. It involves the concepts of BACnet Conformance Classes andFunctional Groups. The Conformance Classes range from 1 to 6. Thestandard states that they are not hierarchical and that Class 1 is notbetter than Class 6.Product Implementation Conformance Statements (PICS) fromvendors determine which products can be used together. BACnetinteroperable systems should be able to provide single-seat operationwhere a central PC operates buildings with control systems furnished byseveral suppliers. It should allow equipment integration including chillers,rooftop units, fire alarm, and lighting control systems.There will be an expanded availability of intelligent devices thatare supplied with intelligent electronic panels or interfaces that communicatewith the host. These will integrate lighting, security, access, andfire alarm controls into one system, so the building can be run from asingle operator interface.BACnet is not a plug-and-play system nor are the otherinteroperable options available today. It is not possible to remove a VAVbox controller and replace it with one from another supplier withoutperforming additional setup and programming. These functions willcontinue to be achieved in a unique manner by each supplier.Interoperable systems allow the following tasks to be accomplishedin a common format:• viewing data on a PC (menus, graphics, reports),• changing setpoints,• sharing data between controllers,• viewing alarms for points that are out of a defined range,• setting up and modifying schedules, and• sampling data at regular intervals and retrieving it for viewing orstorage.The first three functions will be able to be supported by even the©2001 by The Fairmont Press, Inc. All rights reserved.