Specifying Graphics (I/O Summaries) - Honeywell AUTOMATIC CONTROL Engineering Manual

BUILDING MANAGEMENT SYSTEM FUNDAMENTALS
Whereas building control strategies are often established
independent of who will be "operating" the building, operator
graphics should not be. Although the graphic (Fig. 7) presents
an adequate overview of the chiller plant for a building engineer,
it would be overwhelming for custodial or clerical types. They
would not understand the graphic and could cause serious
damage if they issued wrong system commands. Graphic data
compositions must consider the operators ability to understand
and need to know.
Selecting a commandable point presents analog or digital
command options to be executed via dialog boxes, radio buttons,
up-down arrows, etc. Selecting an analog input allows
modification of alarm limit values. Selecting an alarm point
allows entry and modification of the alarm message.
100
33
0
78
78
MINIMUM
ENABLED
BY REMOTE
CONTROLS
ENABLED
ENGINEERING MANUAL OF AUTOMATIC CONTROL
100
33
0
78
COOLING
TOWER
CONTROL
CHILLED WATER SETPOINT
45 46 52
ACTUAL MAXIMUM
CHILLER 1
91
ON 100
AUTO
MAX
OPERATING
STATUS
CURRENT
MODE
AUTO OFF 100
CHILLER 2
85
Fig. 7. Graphic Sketch for Sequence of Operation.

SPECIFYING GRAPHICS (I/O SUMMARIES)

When writing the control sequence of operation, sketch the
graphic (Fig. 7) and note the necessary inputs and outputs
required for control. Develop an Input/Output (I/O) Summary
(Fig. 8) where, the X-axis lists generic types of points and the
Y-axis lists the specific points. Publishing the graphic sketch
with all hardware and software points and symbols is an
excellent alternative to the I/O summary.
DUAL CHILLER PLANT
CONTROL
GRAPHIC DISPLAY
LEAD CHILLER
SELECTOR
1
1 = CHILLER 1 LEADS
2 = CHILLER 2 LEADS
PRESSURE
BYPASS
VALVE
45
AUTO
78
NORMAL
%
ALARM
LOAD
STATUS
00
NORMAL
55
AUTO
194
PRESSURE BYPASS
& CHOKE VALVE
CONTROL
DUAL CHILLER
SETPOINT
REDUCTION
10.5
53
00
PSI
53
45.1
100
PRESSURE
55.0
TO
CHOKE
AHUs
VALVE
CHILLER
CONTROL
SETPOINTS/
SEQUENCES
M15004