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

Control Technology, Microelectronics and NanotechnologyComponent ControlIn the logic components, decisions were based on the physicalparameters connected to it, such as air pressure in a pneumatic controlline coming from a sensor. Every sensor required pneumatic tubing to berun back to the controller. If a change in control logic was desired, itrequired additional labor and materials. This type of control focused onoptimizing components, instead of looking at the dynamic ways of optimizingthe control operation.In a DDC building management system, any point connected tothe system is a part of the data network, capable of providing criticalcontrol information.A component concentration prevents DDC control from using informationfrom anywhere on the network. This can occur if it is implementedonly to consider the same inputs that were used by the systemsof pneumatic controls.Temperature control of a single office in a large complex can illustratethis point. The office temperature might be controlled by a DDCvariable air volume (VAV) box controller with a sensor/thermostat onthe wall. To save energy, a night setback feature is added when there isno one in the office, with the change-over triggered automatically by atime scheduler.The individual office has an installed light fixture and wall switch.To save energy, an occupancy sensor is mounted in the room that turnsoff the light when no one is there.This results in two individually optimized systems that satisfytheir own individual missions of saving energy when the room is notoccupied. But, has the office, as a whole, been truly optimized?In an integrated building management system, every piece of datumis available for use in any strategy and an occupancy sensor tocontrol the DDC VAV box should be used. The occupied/unoccupiedschedule and temperature setpoints are still used, but during occupiedhours, a third standby setpoint is used for damper control of the VAVbox. This would allow the temperature to drift up or down to the predefinedstandby temperature setpoint. This setpoint is used during normaloccupied hours when the occupant is out of the room. The result ismore energy savings at little additional cost.This occupancy sensor could be used to provide security informationas well. Using data generated by the system, security could tellwhich rooms were occupied at any given time.©2001 by The Fairmont Press, Inc. All rights reserved.