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SECTION 14 - ADAPTIVE CAPACITY CONTROL BOARD
FORM 160.54-M1
ISSUE DATE: 10/25/2019
JOHNSON CONTROLS
JCI COMPANY CONFIDENTIAL
14
event that the ACC Board does not find on its own. At
the instant the condition is identified as a surge event,
Surge LED CR9 illuminates for 2 seconds. The mo-
tor speed, Delta P/P and PRV Position at the instant
the point is established, is unconditionally plotted as a
3-dimensional array in the Surge Map as a surge condi-
tion, regardless of whether or not Valid Point LED CR8
is illuminated. The motor speed will be automatically
increased as described above. Once plotted, the ACC
Board will respond to this point in exactly the same
way it responds to automatically plotted surge points,
as described above.
Surge points can be printed from the ACC DETAILS
Screen. The entire stored Surge Map can be printed us-
ing the Surge Map Print keypad key. Also, the surge
points can be printed in real-time as they occur, using
the Auto Print keypad key. Since the maximum rate at
which new surges can be plotted is every five minutes,
the rate at which new points are printed is also every
five minutes.
When the PRV’s approach their 100% open position,
there is very little PRV movement remaining to com-
pensate for an increasing load condition. Therefore,
in Auto Speed Control Mode, if there is no Current
Limit in effect, and the PRV position reaches greater
than 98%, the speed is automatically increased at a rate
based on the Delta T between the Leaving Chilled Liq-
uid Temperature and the Leaving Chilled Liquid Tem-
perature setpoint as follows:
• 0.1 Hz every 10 seconds if Delta T is greater than
0.2 and less than 0.5°F.
• 0.1 Hz every 8 seconds if Delta T is greater than
0.5 and less than 0.9°F.
• 0.1 Hz every 6 seconds if Delta T is greater than
0.9°F.
If Delta P/P ever increases to greater than 3.60, the
speed will be slowly increased to 60Hz. If this were
to occur, Delta P/P would have to decrease to less than
3.55 before a speed decrease would be allowed.
The microprocessor is the center point of the hardware
architecture (
the serial data communications between the OptiView
Control Center Microboard and the VSD Logic Board
and Harmonic Filter Logic Board. This serial data is
in 0 to 5 VDC form. LED’s YM XMT (CR7) and YM
RCV (CR6) LED’s illuminate during serial communi-
cations with the OptiView Control Center Microboard.
Similarly, VS XMT (CR5) and VS RCV (CR4) LED’s
illuminate during serial communications with the
VSD Logic Board. Serial communications with the
Harmonic Filter Logic Board take place through the
microprocessor via the Digital Signal Processor. This
data is accompanied by a Framing pulse and a CLK
signal. Although Evaporator and Condenser Pressures
are transmitted to the ACC Board via the serial com-
munications link for Delta P/P calculation, these pres-
sures are also applied directly from the microboard to
the MUX (multiplexer) for Delta P surge detection.
Also applied to the MUX, is the output of the PRV po-
sition potentiometer. Under Program control, these val-
ues are input to the microprocessor. The EPROM con-
tains the operating program for the ACC Board. The
RAM serves as the scratch pad memory. The BRAM
is a battery backed memory device where the Surge
Map is stored. The Watchdog circuit maintains the mi-
croprocessor in a reset state during low voltage con-
ditions. This prevents the microprocessor from read-
ing/writing or processing data until it and supporting
circuits have sufficient supply voltage. The Watchdog
also ensures that the entire Program is executed and
that no Program latch-ups occur.
S
urge LED CR9 il-
luminates for 2 seconds when a valid surge condition
has been detected as explained above. Valid Point LED
CR8 illuminates whenever there is a condition in effect
that prevents a Surge from being plotted on the Surge
Map. These conditions are:
• Current Limit is in effect.
• Leaving Chilled Liquid Temperature Stability
Timer is running, indicating an unstable control
condition.
• Speed control is in Manual Mode.
Switch SW1 is used to manually insert (plot) a surge
point in the Surge Map.
Test points are provided as follows:
• TPA: +5 VDC supply voltage.
• TPB: supply voltage ground.
• TPC: Watchdog power failure detected. Normally
greater than +4.5 VDC. Transitions to logic low
(less than 3.5 VDC) during low voltage conditions.