219
FORM 160.54-M1
ISSUE DATE: 10/25/2019
JOHNSON CONTROLS
JCI COMPANY CONFIDENTIAL
25
SECTION 25 - SURGE PROTECTION
The Surge Protection feature detects surge events for
Surge Avoidance and the Hot gas bypass feature. It
provides a running count of the surges detected over
the lifetime of the chiller. It allows the user to define
how many surges are excessive and how the control
will react to an excess surge condition. When excessive
surging is detected, it can be configured to shutdown
the chiller or initiate a Surge Correction/Avoidance
Mode or simply display a warning message.
The detection and counting of surges in this feature is
independent of the surge detection/counting performed
by the Compressor Motor Variable Speed Drive (VSD)
Adaptive Capacity Control (ACC) surge detection.
The ACC surge detection creates a surge map used
to control the speed of the drive. In new production
chillers before March 2007, the ACC function and
ACC surge detection are performed by the ACC Board
(this is called the YORK Protocol configuration). In
new production chillers after March 2007, the ACC
surge detection is performed by the ACC function in
the microboard and the ACC Board is not present (this
is called the Modbus Protocol configuration). All Me-
dium Voltage Variable Speed Drives (MV VSD) use
this later configuration. The surge events detected and
accumulated by the ACC function are displayed on the
ACC Screen.
With software version C.OPT.01.19.307 and later (in
Modbus Protocol configuration), there’s an “ACC
Surge Detected” LED on the SURGE PROTECTION
Screen that annunciates the ACC detected surges. This
is provided on this screen for reference only. To elimi-
nate counting and reacting to surges caused by the ACC
function, the Surge Protection feature only detects and
reacts to those surges that occur while the VSD is run-
ning at maximum frequency (speed). See
MICROBOARD 031-02430-000 AND 031-02430-001
and
SECTION 14 - ADAPTIVE CAPACITY CONTROL
of this manual for details of these configura-
tions. Due to service parts replacement, early produc-
tion chillers could be in the Modbus Protocol configu-
ration.
The SURGE PROTECTION Screen, accessible from
the COMPRESSOR Screen, displays all parameters
relevant to this feature. All setpoints for this feature are
maintained on this screen. The parameters displayed
on this screen vary according to the software version
and compressor motor type as noted below.
SURGE DETECTION
Surge events are detected by monitoring the relation-
ship between the Condenser Pressure and Evaporator
Pressure while the chiller is running. When the dif-
ference between these pressures decreases transiently
and remains so for a period of time described below,
and then makes a positive transition within 7 seconds
(90 seconds with software version C.MLM.01.10B.
xxx and later) or C.OPT.01.10B.xxx and later), a surge
event has been detected.
The surge detection sensitivity for the Surge Protec-
tion feature is set with the Surge Sensitivity setpoint
on the SURGE PROTECTION Screen. It is adjustable
over the range of 0.3 (default) to 1.3. Smaller values
increase the sensitivity. This sensitivity setting is not to
be confused with the Surge Sensitivity setpoint on the
ACC DETAILS Screen. The Surge Sensitivity setpoint
on that screen adjusts the sensitivity of the ACC Surge
Detection feature in the microboard when configured
in Modbus Protocol configuration (software version
C.OPT.01.16.307 and later).
The Evaporator Pressure Transducer output is subtract-
ed from the Condenser Pressure output to determine the
differential. If either of the following negative transi-
tions occur in the differential followed by a 0.061 VDC
positive differential transition within 7 seconds (90
seconds for P and Q compressors with software ver-
sion C.MLM.01.10B.xxx and later) or C.OPT.01.10B.
xxx and later), a surge event is detected:
• If the differential decreases more than 0.6 VDC
for more than 0.260 seconds.
• If the differential decreases more than x.x VDC
for more than 0.390 seconds.
x.x VDC calculated as [(Surge Sensitivity
setpoint x 300) x 1.22] ÷ 1000
Each time a surge is detected by the Surge Protection
feature, the Surge Avoidance Surge Detected indica-
tor illuminates momentarily (if equipped with a VSD
or MV VSD, this feature only detects surges while the
drive is running at maximum frequency). If equipped
with software version C.OPT.01.18.307 or earlier, the