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SECTION 14 - ADAPTIVE CAPACITY CONTROL BOARD
MODBUS PROTOCOL CONFIGURATION
In Modbus Protocol configuration (Microboard 031-
02430-001 with software version C.OPT.01.16.307
and later), the ACC function is in the microboard and
the ACC Board is not present. The microboard com-
municates directly with the VSD Logic Board through
the Modbus serial communications (See Figure 64 on
page 154). All the commands to the VSD and data
from the VSD are via this communications link. Gen-
erally, the serial communications and data transfer
and shutdown status is as described in YORK Protocol
Configuration on page 143.
The ACC DETAILS Screen displays the pertinent
ACC parameters as shown in OptiView Control Panel
– Operation (Form 160.54-O1) FIGURE 35. (Software
version C.OPT.01.19.307 (and later) provides the pa-
rameters in this description). The ACC function in the
microboard performs the ACC surge detection. ACC
surges are detected only when the drive is running
at less than maximum frequency. With software ver-
sion C.OPT.01.19.307 (and later), the surge detection
and reaction routine is disabled until 5 seconds after
the start frequency (25Hz for 50Hz applications/30Hz
for 60Hz applications) is achieved. This prevents false
surge conditions from being logged or reacted to.
The VSD Start Frequency setpoint (software version
C.OPT.01.21.307 and later) allows the Service tech-
nician to enter the starting frequency from which the
speed ramp-up will begin. This setpoint is program-
mable over the following range:
A. 60 Hz units – 30 Hz to 60 Hz (default 45 Hz)
B. 60 Hz units with Quick Restart- 30 Hz to 45 Hz
(default 45 Hz)
C. 50 Hz units – 25 Hz to 5 0Hz (default 37.5 Hz)
D. 50 Hz units with Quick Restart – 25 Hz to 37.5 Hz
(default 37.5 Hz)
The Surge Sensitivity setpoint is used to adjust the sen-
sitivity of the ACC surge detection. It is programmable
over the range of 1.5 to 2.5 (default 2.0); smaller val-
ues increase the sensitivity. Whenever an ACC surge
is detected, the "ACC Surge Detected" LED momen-
tarily illuminates and the "ACC Surge Count" incre-
ments (The "Surge Avoidance Surge Detected" LED is
shown for reference only. It momentarily illuminates
150
when the Surge Protection feature (See SECTION 25
- SURGE PROTECTION ) detects a surge. These are
only those surges that occur while the drive is running
at maximum frequency. This LED should not be con-
fused with ACC detected surge events).
The ACC Mapping Enable setpoint 0.5°F to 20.0°F
(default 1.0°F). 0.5°F to 4.0°F (software version
C.OPT.01.22.307 and earlier) allows the Service tech-
nician to set the Delta T (Leaving Chilled Liquid Tem-
perature minus setpoint) needed to be met to enable
surge mapping and speed reduction initially on startup.
Software version C.OPT.01.19.307 (and later) has in-
creased noise filtering on the surge detection. Valid
ACC surge points are stored in the Surge Map in the
microboard BRAM, as displayed on the SURGE MAP
Screen (see below). "Surge Map Point Count" displays
the total number of data points contained in the surge
map. Based on this surge detection, the speed com-
mand is sent to the VSD Logic Board and displayed on
the ACC DETAILS Screen as "Command Frequency".
The "Speed Decrease Inhibit – Surge Map Point" LED
illuminates when the speed cannot be reduced due to a
mapped point. The "Mapping Inhibited" LED illumi-
nates while a point is not allowed to be mapped (not
allowed to slow down as well) due to unstable leav-
ing chilled liquid temperature, manual speed control or
current limit in effect.
With software version C.OPT.01.21.307 (and later),
Surge Mapping is inhibited while a Soft Shutdown is
in effect. In software versions C.OPT.01.20.307 (and
earlier), if 2 surges are detected during the initial ramp
(ramp towards maximum frequency after reaching
start frequency), the command frequency is set to the
maximum frequency regardless of motor current. This
can result in motor current rising sharply and forc-
ing vanes to have to close hard and even possibly a
trip on high current or overload. In software version
C.OPT.01.21.307 (and later), for every 2 surges that are
detected during the initial ramp, increase the command
frequency (no higher than the maximum frequency) by
the amount listed in the following table. After increas-
ing the command frequency, the initial ramp surge
count is reset so it can react to another 2 surges and the
initial ramp shall be continued. This logic shall be in
effect during the entire initial ramp and take action as
many times as necessary.
JCI COMPANY CONFIDENTIAL
FORM 160.54-M1
ISSUE DATE: 10/25/2019
JOHNSON CONTROLS
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