humidity in a specific area and based on the measurement, direct cooling, heat-
ing, humidifying, or dehumidifying to that area.
Some mechanical equipment, such as air-handling units or chillers, may be
procured with a field-level controller and devices as part of the equipment.
System controllers allow field controllers to communicate with other field con-
trollers or a group of field controllers, and to access databases and programs.
DDC controllers can also use remote application-specific controllers (ASCs)
for devices such as VAV terminal units.
HVAC control systems are evolving to the utilization of smart building
infrastructure. This is true of the HVAC system management level, and is evol-
ving or trickling down to the network hierarchy at the system and field level.
The adoption of ANSI/TIA/EIA-862 addressing–structured cable infrastruc-
ture for building automation systems allows for standard unshielded twisted
pair copper cabling and fiber optic cabling to be utilized throughout an HVAC
control system.
Although the IP network protocol may be used at the management level,
BACnet or LonTalk are likely to be used at other levels. However, these other
protocols recognize the dominance of the IP protocol and are either providing
routers for transitioning from their native protocol to IP (LonTalk) or are
migrating to IP with standards such as BACnet/IP.
46 Smart Building Systems for Architects, Owners, and Builders