Book - School of Science and Technology

Chapter 22Automatic controls and building managementsystemsControls theory and practice is an extremely broad and complex subject. It is possiblehere to give only a general overview of the more important principles and to outline someof the more common practices. For further details, the reader is recommended to consulteither a specialist text or a more comprehensive digest.*The controls philosophy must be developed together with that of the systems designsince, in the final installation, the two have to operate in harmony. However accurate theselection of equipment for a given application, if the controls are sub-standard as todesign, installation, commissioning or maintenance then the performance of the overallsystem is unlikely to meet the design requirements.The popular adage keep it simple applies to controls perhaps more particularly than toany other aspect of heating and air-conditioning. There is no benefit gained if the designerproduces a system of controls which is beyond the comprehension of those personnelresponsible for the operation and maintenance of the completed installations. By way ofexample, a full building management system might be operated as no more than anexpensive time switch if that is the level of understanding of the operators: a controlsystem must be designed for the user and not to satisfy the ambitions of the designer.Conversely the optimisation abilities of a well designed control system can reap considerablesavings for the operators.There has been a very considerable development in the application of controls since theintroduction of computer technology. This has been particularly marked in the case ofbuilding and energy management systems, where significant benefits in the conduct ofplant operation, maintenance and economy in running are available. The topic is dealtwith towards the end of this present chapter.The main objectives of a controls system may be summarised as:. safe plant operation. protection to the building and system components. maintenance of desired conditions. economy in operation.* Building Control systems: CIBSE Guide H 2000.