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HVAC
Application
The
rising cost of energy and drive for efficiency has resulted in
more intelligent Heating, Ventilation and Air Conditioning (HVAC)
control systems within commercial buildings and manufacturing
facilities. PLCs are
commonly used to measure and control HVAC distribution systems.
Feedback loops and damper controls direct the flow of
conditioned air to particular zones.
Filtration systems are also monitored for efficiency and
maintenance purposes.
Samsung
Korea determined that a higher level of control was necessary for
a new semi-conductor manufacturing plant. An initiative to further improve these building control
systems identified the fact that the heating and cooling
generation systems could be controlled to a higher degree of
efficiency. In order to
implement these efficiencies, it was necessary to monitor current
system flow, total flow, temperature and density.
The cost of implementing discrete sensors for these
measurements was prohibitive. After
further evaluation, it was determined that a HART-enabled
flowmeter could provide all the necessary data.
The
next step was to identify an interface to the flowmeter that would
allow a full read/write dialog and provide data quickly and
efficiently to the PLC.
Spectrum
Controls Analog I/O with HART Protocol was selected.
A series of four 1756sc-IF8H analog input modules were
interfaced to Rosemount Magnetic Flowmeters and Probar Mass
Flowmeters to obtain system flow, total flow, temperature and
density. Through the use of
simple ladder logic, the I/O modules allow the totalizer of each
meter to be reset when necessary by sending a HART command from
the PLC. All this was
accomplished without any additional wiring and with nominal cost
impact.
The
result is a higher level of heating and cooling efficiency and a
better window into the data used to control the overall system
operation. Analog
I/O with HART Protocol simplified the task of incorporating
HART data into the PLC control routines and provides a window to
this data with a higher level of system control.
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