ABSTRACT
HVAC controls have been likened to the nervous system of the human body which receives and sends signals from and to the various organs to enable them to perform their functions properly. One of the major causes of energy inefficiency in actual buildings is due to controls not performing as intended. Though this is often an issue with building operation and maintenance, the building designer should also be familiar with HVAC controls in order to be able to perform his/her job satisfactorily. This chapter deals with several aspects relevant to building HVAC control systems. The introductory review includes a brief discussion of local and supervisory control, the elements of a control system, and the role of the control designer. We then describe the four different modes of feedback control after which a discussion of the major types of control hardware (pneumatic, electronic, and DDC) is presented. Subsequently, various control components are discussed followed by examples of important HVAC control systems and control sequences relevant to large cooling systems. This chapter, though primarily meant to cover local control issues, also touches upon building automation systems (BAS) and energy management systems (EMS) or energy management or control systems (EMCS). We also briefly describe data exchange/communications protocols such as BACnet. This chapter concludes by providing basic mathematical concepts of local control theory related to modeling, control stability assessment, and control system simulation.
