ENGINEERING MANUAL OF AUTOMATIC CONTROL
BUILDING MANAGEMENT SYSTEM FUNDAMENTALS
193
Controller Support
A major portion of the BMS Software is the definition and
maintenance of system-level controller software. The software
allows viewing and editing setpoints and parameters, up or
down loading controller databases, adding and editing points
and programs, and executing diagnostics.
OPERATION
Operator access to the system is usually positioning the
cursor (via a mouse) on a graphic display of a system.
Following are examples of BMCS automation concepts for a
two building facility with boilers, chillers, and VAV air
handlers. When an authorized operator signs on to a system
PC, the system recognizes the access authority and presents
the top level graphic (Fig. 5)
—AUTO/OFF (10 points) are commandable. Cursor
selection of these points, allows commanding points ON
or OFF.
— 45, 55, 78, 136 (5 points) depict the current hot and chilled
water discharge temperatures.
— 55, 56, and 57 (5 points) depict the current discharge air
temperatures of AHU A-D and AHU R.
— 62, 66, 71, 76, 77 (5 points) depict the current AHU A-D
and AHU R VAV fan speed.
— 516 and 771 indicate the instantaneous building
kilowatt use.
In Figure 5 the AUTO/OFF points, the hot and chilled water
discharge temperatures, and discharge air temperatures typically
would be alarm points. They will respond similarly to a
NORMAL/ALARM point if they are not as commanded or not
within acceptable limits.
Operator selection of the “CHILLER A1 CHILLER A2”
icon displays the graphic shown in Figure 7 which has 42
data points and three icons for subsequent penetration,
summarized as follows:
4 Cooling tower isolation valve position indicators.
2 Cooling tower % fan speed indicators.
9Temperature indication points.
2 ON-OFF-AUTO command points for each chilled
water pump.
4 Pump dynamic symbols (On—green, Off—yellow,
unacknowledged alarm—red flashing, acknowledged
alarm—red).
2 Control command status display points to indicate
status of control command to each chiller system.
2AUTO-OFF command point for each chiller.
2 Chiller status indicators.
2 Maximum % load commandable current-limiting
points.
2% maximum current indicator for each chiller.
2Alarm status indicator for each chiller.
2 Commandable chilled water temperature minimum
and maximum setpoints.
1 Current chilled water temperature setpoint indicator.
2Pressure control valve % open indicators.
3Pressure control points; current value and command-
able setpoint for differential pressure bypass value,
and the commandable differential pressure offset value
to be subtracted when both chiller pumps are operating.
1 Commandable lead chiller selector.
1 Icon for a subsequent cooling tower control graphic(s)
with setpoints and sequences.
1 Icon for a subsequent pressure bypass and choke valve
control graphic(s).
1 Icon for a subsequent chiller control setpoints and
sequences graphic.
Fig. 6. Graphic Symbols used on Graphic Displays.
Each graphic should contain dynamic system information.
Graphic 1 includes 44 points of dynamic system information
(rectangular boxes), and eight penetration icons, summarized
as follows:
— AHU A-D, AHU R, CHILLER A1 CHILLER A2, MER
R, and BOILER A are icons. Selecting an icon displays
the appropriate next level graphic.
— 81 and 51 are the current outside air conditions. These
values and the other dynamic data points shown are
required elsewhere for control and/or automation. Since
they are required elsewhere they are in the data base and
available to put meaning in this top level facility graphic.
—ON, OFF (10 points) shows the current status of the air
handlers, boilers, and chillers.
— NORMAL (5 points) shows the current status of the boiler
and chiller controls. These are monitor/automation points
not required for control. In an alarm condition, the text
changes to ALARM, the point turns to red, and the red
blinks until an authorized operator acknowledges the alarm.
100
SYMBOL LEGEND:
DYNAMIC VALUE
TEMPERATURE
HUMIDITY
COMMANDABLE ANALOG VALUE
COMMANDABLE ANALOG VALUE DIGITAL POINT
DIFFERENTIAL PRESSURE POINT
DYNAMIC PUMP SYMBOL
ICON FOR SUBSEQUENT GRAPHIC SELECTION
M15020
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