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

HVAC Control in the New Millenniumdowntimes or producing defective products.Energy controls are only part of an environmentally consciouspolicy. Modern civilization is electricity based, but over the past 20 yearsmost of the energy savings has mainly been in heating.Energy Management DevicesEnergy management devices are used to regulate the on and offtimes of selected loads, such as fans, heaters, and motors. They are usedin a building in order to reduce electrical demand (kilowatts) and toregulate energy consumption (kilowatt hours). Energy managementdevices can be electromechanical, electronic, or computer based.The operation of one or more loads is interrupted by the energymanagement system based on control algorithms and building-operatingparameters, such as temperatures, air flow, or occupancy. The savingsin electrical energy use and cost range from 0 to 50% or more.Electrical DemandElectrical demand is defined as the average load connected by auser to an electrical generating system. It is measured over a short, fixedperiod of time, usually 15 to 30 minutes. The electrical demand is measuredin kilowatts and recorded by the generating company meter foreach measurement period during the billing month. The highest recordedelectrical demand during the month is used to determine the costof each kilowatt hour (kWh) of energy consumed.Demand Load SheddingEnergy management devices, such as load shedders, reduce thedemand (average load) in critical demand periods by interrupting electricalservice to motors, heaters, and other loads for short periods. Sincethe load which has been turned off would normally have been operatingcontinuously, the overall effect is to reduce the average load or demandfor that period of time (Figure 2-3). The instantaneous load when theload is operating remains the same. If the period involved has the high-©2001 by The Fairmont Press, Inc. All rights reserved.