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SECTION 25 - SURGE PROTECTION
indicator is labeled Surge Detected and it illuminates
whenever a Surge Detected, regardless of VSD operat-
ing frequency.
If equipped with a VSD (in Modbus Protocol configu-
ration) or a MV VSD, the ACC Surge Detected indica-
tor illuminates momentarily when a surge is detected
by the ACC function in the microboard, while the drive
is running at less than maximum frequency. Software
version C.OPT.01.18.307 or earlier does not have this
indicator.
The Surge Avoidance Surge Count (displayed as "To-
tal Surge Count" in software version C.OPT.01.18.307
and earlier) is the total number of surges detected by
the Surge Protection feature (if equipped with a VSD
or MV VSD, this feature only detects surges while
the drive is running at maximum frequency). The
Surge Avoidance Surge Count can be cleared using an
ADMIN password following procedure in SECTION
33 - SYSTEM CALIBRATION, SERVICE SETPOINTS,
AND RESET PROCEDURES of this manual.
The Surge Window Count accumulates the number of
surges that occur within the Surge Window Time. This
time is programmable over the range of 1 to 5 minutes
using the Count Window setpoint. The number of surg-
es that occur within the Surge Window Time are com-
pared to the Count Limit setpoint (4 to 20) to determine
if an excess surge condition exists, as explained below.
EXCESS SURGE DETECTION
An excess surge condition is detected by comparing
the number of surge events that occur in a selectable
time period to a selectable threshold.
If the number of surge events (Surge Window Count)
detected in the time period programmed as the Count
Window setpoint (1 to 5 minutes; default 5) (default 3
with Software version C.MLM.01.09.xxx (and later) or
C.OPT.01.09.301 (and later)) exceed the threshold pro-
grammed as the Count Limit setpoint (4 to 20; default
4) (default 15 with Software version C.MLM.01.09.xxx
(and later) or C.OPT.01.09.301 (and later)) an excess
surge condition has been detected.
Unless the Shutdown or Extended Run features have
been enabled, as explained below, the chiller will
continue to run under the same conditions displaying
WARNING – EXCESS SURGE DETECTED. This
message will be displayed until manually reset with the
WARNING RESET key in OPERATOR access level.
220
SURGE PROTECTION
The Control Center can be configured to take the fol-
lowing courses of action when an excess surge condi-
tion has been detected. The Shutdown setpoint is used to
invoke a safety shutdown. The Extended Run setpoint
is used to invoke a special 10 minute Surge Correction/
Avoidance Mode that temporarily eliminates the con-
ditions causing the surging, while allowing the chiller
to continue to run. If the chiller is equipped with the
Hot gas bypass feature and/or a Compressor Motor
Variable Speed Drive (VSD), certain Hot gas valve po-
sition and VSD speed criteria must be met before the
Shutdown or Extended Run functions are performed as
explained below.
When a surge is detected, the following courses of ac-
tion are taken:
• If the Shutdown setpoint is enabled, and the Ex-
tended Run setpoint is disabled, a safety shutdown
will be performed and SURGE PROTECTION -
EXCESS SURGE is displayed.
• If the Shutdown setpoint is disabled and the Ex-
tended Run setpoint is enabled, the Pre-rotation
Vanes are driven closed for 10 minutes and
WARNING – SURGE PROTECTION – EX-
CESS SURGE LIMIT is displayed. When the
10 minutes have elapsed, if the Surge Window
Count is less than or equal to the Count Limit,
this message and load inhibit are automatically
cleared, otherwise another 10 minute period is
initiated. Alternating with this message is WARN-
ING – EXCESS SURGE DETECTED that is dis-
played until manually reset with the WARNING
RESET key in OPERATOR access level. During
the 10-minute period, a countdown timer on the
SURGE PROTECTION Screen displays the time
remaining in the period. See Hot gas bypass and
Compressor Motor Variable Speed Drive excep-
tion above.
• If both the Shutdown and Extended Run setpoints
are enabled, the 10 minute Extended Run period
is invoked as above. However, if the Surge Win-
dow Count exceeds the Count Limit at the end of
the 10 minute Extended Run period, a safety shut-
down is performed and SURGE PROTECTION
– EXCESS SURGE is displayed.
JCI COMPANY CONFIDENTIAL
FORM 160.54-M1
ISSUE DATE: 10/25/2019
JOHNSON CONTROLS
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