The cost per point for the DDC systems is usually higher than that of the other classes, but the following additional benefits are often sufficient to justify the extra cost. DDC systems are expandable in terms of the number of points able to be monitored, software packages available, and operational functions. They are more reliable than pneumatic control systems. Failure of the central facility does not upset the individual control units because satellite processing units are programmed to stand alone in such cases. Larger computer memory allows the building management to use a preventive maintenance program and perform energy audits for the different buildings.
Electronic components are usually available from several computer manufacturers.
This has the advantage that the customer is not restricted to a particular company for equipment maintenance, and, in most cases, results in a reduction in the operation cost of the system. Although the initial cost of DDC systems is relatively higher, the payback period is comparable with those of smaller systems. Concluding Remarks Building automation systems contribute to energy conservation and save money because of better control of energy consuming equipment. CCMS indicate off-normal conditions before they are registered as a complaint about uncomfortable conditions in the occupied space. CCMS provide maintenance personnel the convenience of checking the HVAC components without actually having to visit the system.