Honeywell AUTOMATIC CONTROL, Engineering Manual

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ENGINEERING CMANUAL OF AUTOMATION CONTROL
AIR HANDLING SYSTEM CONTROL APPLICATIONS
206
17. PLACE CONTROL VALVES ON THE LEAVING SIDE
OF WATER COILS.
Control valves on the leaving side of water coils
leaves pressure in the coil when the valve is
closed, thus aiding in eliminating air through the
air vent on the leaving side of the coil, and also
prevents the possibility of air being induced into
the system through the vent if the pump produces
a negative pressure in the coil return line.
18. CONSIDER THE ABILITY OF THE HVAC SYSTEM
OPERATOR TO UNDERSTAND THE SYSTEM
WHEN DESIGNING GRAPHICS FOR THE
OPERATOR INTERFACE.
APPLICATIONS-GENERAL
The following applications are presented in a DDC format
using notation from the Symbols in this section. In some cases
the degree and complexity of control shown is not practical in
other forms of control.
Suggested microprocessor data points are shown as they could
appear on a color graphic display of a PC operator workstation.
In some cases data points, other than those required for control
and operation, are shown to help an operator understand the
loading and performance of the HVAC system and related
control loops. If a PC station is not required, the data points
required for control and operation should still be specified for
the operator by listing the points or including a graphic sketch.
Values, setpoints, gains, timings, etc. shown in these examples
are general, and actual values should be determined on a project-
to-project basis.
The following applications were selected for this section on
Air Handling System Control Applications. Caution should be
used in simply combining any of these applications together as
a control solution for a more complex system. Application
variations may be required depending on the heating, cooling,
and pumping configurations, the building use and occupants,
the ability of control vendors and related control systems, the
ability of local operating and maintenance persons, codes, and
weather.
Lines connecting inputs, outputs, values, and control
functions have been added to aid in understanding. In many
cases these lines would create unacceptable clutter on an actual
system graphic display. Graphic display and management
function (alarms, records, etc.) concepts are discussed further
in the Building Management System Fundamentals section.
Although the control solutions presented are good general
recommendations, other solutions are acceptable, and in some
cases, may better depending on the job objectives.