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SECTION 14 - ADAPTIVE CAPACITY CONTROL BOARD
• Delta P must make a negative transition and ex-
ceed 3.4 psig for 100 milliseconds.
• Delta P must also exceed 3.5 psig for at least 340
milliseconds.
• Delta P must make at least 2 positive transitions.
When this criteria is met, Surge LED CR9 illuminates
for 2 seconds, indicating a valid surge has been detect-
ed. In detecting a surge using the DC Link method, the
VSD's DC Link Current is monitored to detect when
the current drops transiently toward zero. This, as the
case with Delta P method, is indicative of a surge. A
Surge Detected by this method must also meet the fol-
lowing requirements to be considered a valid surge:
• At least 6 DC Link surges must occur within 2
minutes, and
• At least 3 Delta P surges have occurred within the
2 minute interval.
When both these criteria have been met, Surge LED
CR9 illuminates for 2 seconds, indicating a valid surge
has been detected. The value displayed as ACC SURGE
COUNT on the ACC DETAILS Screen is provided by
the ACC Board. Each time the ACC Board detects a
surge, the ACC Board increments the count, whether
running at maximum or less than maximum frequency.
Each time a Valid Surge is detected, the ACC Board
increases the motor speed (up to a maximum of 60 (50)
HZ) to take the compressor out of surge. It also evalu-
ates other chiller conditions to determine if the surge
should be plotted on the Surge Map. Surges that occur
during certain operating conditions are not plotted, as
explained below. Whenever Valid Point LED CR8 is
illuminated, surges are not plotted.
After each surge, the speed is increased either 1.0Hz or
0.8Hz, depending on operating conditions, in the fol-
lowing increments:
• 0.1 Hz every 2 seconds if motor current less than
80%FLA.
• 0.1 Hz every 2 seconds + (%FLA-80) if motor cur-
rent greater than 80% FLA but less than 98%FLA.
• 0.1 Hz every 20 seconds if motor current greater
than 98% FLA.
If Current Limit is in effect, or the Stability Timer is
running when a surge occurs, the speed is increased
1.0Hz but the surge is not plotted on the Surge Map
since these conditions would produce an erroneous
148
value. Valid Point LED CR8 is illuminated as a visual
indication that one or both of these conditions are in
effect.
Otherwise, the speed is increased 0.8Hz and the surge
event is plotted on the Surge Map. The Surge Margin
Adjust setpoint can be used to add an extra margin of
surge prevention. It is programmed over the range of
0.0 to 25.0Hz following instructions in SECTION 31 -
SYSTEM CALIBRATION, SERVICE SETPOINTS AND
RESET PROCEDURES of this manual. The Default
value of 0 should provide proper operation in most ap-
plications.
When the speed has been increased either 1.0Hz or
0.8Hz, as described above, this speed is maintained for
the next 15 seconds. During this period, new surges are
ignored. When the 15 seconds have elapsed, a 5 min-
ute time period is entered where the speed is inhibited
from decreasing, but increases are allowed. If a surge
is detected within this 5 minute period, it is not plotted
on the Surge Map, but the speed is increased by the
amount as described above. This is repeated as long
as the compressor continues to surge. The compressor
must be surge free for 5 minutes before a speed de-
crease is permitted or another surge can be plotted on
the Surge Map.
The ACC Board counts the surges as they occur and
sends a total count to the microboard for display on
the ACC DETAILS Screen (note that the Total Surge
Count displayed on the SURGE PROTECTION
Screen and the Hot gas bypass Screen is that which is
accumulated by the Surge Protection feature). The total
surge count is not incremented if a different surge type
occurs within 10 seconds of the previous surge. A surge
that occurs within 10 seconds of the previous surge is
only counted if it is of the same surge type. For exam-
ple, if a Delta P surge is detected and a DC Link surge
is detected within 10 seconds, the DC Link surge is not
counted. If the DC Link surge occurred greater than 10
seconds after the Delta P surge, it would be counted.
A surge point can be manually inserted into the Surge
Map using the Manual Surge Point keypad key on the
ACC DETAILS Screen and switch SW1 on the ACC
Board as described in SECTION 33 - SYSTEM CALI-
BRATION, SERVICE SETPOINTS, AND RESET PRO-
CEDURES of this manual. This is only to be used for
situations in which the automatic surge detection de-
scribed above does not respond to surge events. This
is usually not required and is to be used only by quali-
fied Service technicians as a method of plotting a surge
JCI COMPANY CONFIDENTIAL
FORM 160.54-M1
ISSUE DATE: 10/25/2019
JOHNSON CONTROLS
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