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

HVAC Control in the New Millenniumterrogation. Devices can provide automatic safety actions to preventdangerous conditions. Diagnostics may be checked directly from theoperator console or from hand-held terminals.Continuous device self diagnostics can be reported as events aswell as configuration diagnostics. User-invoked diagnostics tests can beused to check damper and valve operation.Modern HVAC controls must maintain accurate and reliable measurementsto achieve lower operational costs. Fouling of sensors may bedetected as well as faulty or poor wiring. Long-term drifts or shifts dueto conditions or aging can be detected if there is a comparison againstan external reference providing calibration.Positioner diagnostics can include diagnostics of actuators andvalves. Valve positioner diagnostic information can include valve stemfriction and other parameters. Statistics on cycle count and time in operationcan be recorded to estimate wear and tear and predict failures.Other data from the positioner can be used to determine positioner andvalve characteristics, such as valve position travel time.Stored device information includes tag and serial numbers, characteristicsand date installed. Storing the information in searchable andsortable databases for easy access reduces errors and makes calibrationand preventive maintenance less costly while ensuring it is done correctlyand on a periodic basis. The result is better measurement andcontrol.Fieldbus places new requirements on host operator interface software.Older distributed control systems (DCS) and PC-based softwarewas designed in an era when field devices provided only a single value.With fieldbus, there is a huge increase in diagnostic and other data.Some of these are continuously updated and others are updated asalert reports. Others are static and updated only when they change.The information had to be entered for each parameter can includenode address, data file and memory address. Data type and display andalarm information may also be applicable to some parameters.Since fieldbus devices are standardized and based on user-definedtags, the user can specify the tag of a function block or device and all thediagnostics and pieces of information associated with that tag are automaticallyconfigured in detail.Automated configuration generation reduce the number of hoursto make a configuration and users will get more data easier and in lesstime.©2001 by The Fairmont Press, Inc. All rights reserved.