Civil Engineering Reference
In-Depth Information
Communication gateways are the tools that do the translation between two different
communication protocols. In addition to translation between the proprietary and
open systems, it also can be used to translate between equipment designed with dif-
ferent manufacturers inside a new open system. The faster and the better this trans-
lation is executed the higher is the interoperability of the communication gateway.
Other notable elements in a control network system are local area network (LAN)
that is a system for sharing information between different DDC systems, system
integrator that ensures the information exchange between the two networks through
the communication gateway is being done precisely, and routers that are used to
convert data link layer protocols and do not require to translate between languages.
DDC controllers interact with different elements of the system through inputs
and outputs signals that receive information from sensors and send command to
actuators respectively. Auxiliary elements are devices such as control valves and
dampers, and operator interface is a software package that monitors and controls the
operation of the system.
9.5
Sequence of Operation
Since the control system designer, system installer, commissioning agent that over-
view the installation of the system and the building engineering staff whom after the
delivery of the building overviews the daily operation of the building are different
people, and since controlling the building operation is an ongoing procedure that
last throughout the life of the building, there is a vital need for the designer to
clearly describe what his targets of system functionality under different conditions
and situations are. This helps the control contractor to install the system and pro-
gram it properly, commissioning agent to point out the diversions of the installation
versus the designer's plan more easily, and building staff to maintain and trouble-
shoot the system as per designer's guidelines without need for any kind of guessing.
This is usually done with a well written sequence of operation and schematic con-
trol diagram as part of the design document, in which the designer depicts and
describes his expectations of functionality of the system as the building external and
internal conditions change.
In writing a sequence of operation, the designer should be very specifi c and
detail-oriented, describes all the possible conditions, and answers all the probable
questions regarding the system operation under different conditions, in order to sim-
plify the understanding and therefore interaction of the other involved individuals as
described above with the control system. In pursuing this goal the control system
designers usually divide the whole HVAC system into its smaller entities such as
chillers, boilers, air handling units, fan coil units, etc., and thoroughly describes
their expectations of each equipment functionality. Generally the target of a HVAC
control system is to monitor or control parameters such as temperature, pressure,
humidity, fl ow, carbon dioxide level, and fi lter pressure drop. Therefore a complete
set of guidelines should be provided to defi ne the desired set points of each of these
