York YK-EP Operation And Maintenance Manual page 194

Warning – External I/O – Serial Communications
Serial communications between the Microboard and the optional Analog I/O Board has been
interrupted for at least 20 seconds.
Warning – Excess Surge Detected
(Applies only if Surge Protection Shutdown feature is Disabled)
The Surge Window Count has exceeded the Count Limit. Message can be manually cleared after the
Surge Window Count is less than or equal to the Count Limit, or the Shutdown feature is enabled or
the chiller is stopped. To clear message press WARNING RESET key on HOME Screen when logged
in at OPERATOR (or higher) access level.
Warning – Surge Protection – Excess Surge Limit
(Applies only if Surge Protection Extended Run feature is Enabled)
Displayed during the Surge Protection 10 minute Extended Run period. This period begins when
the Surge Window Count exceeds the Count Limit. During this period, the Pre-Rotation Vanes are
driven closed. When 10 minutes have elapsed, this message and the Pre-Rotation Vanes load inhibit
are automatically cleared. Message and load inhibit are also cleared when the chiller is shutdown.
Note: If the optional Hot Gas Bypass feature is enabled, the valve position must be at 100%
before the Extended Run is implemented. If the chiller is chiller is equipped with a Compressor
Motor Variable Speed Drive, the output frequency must be at full speed (50 Hz/60 Hz) before
this control can be implemented.
Warning – Condenser Or VGD Sensor Failure
The difference between the Stall Pressure transducer output and the Condenser Pressure
transducer output has exceeded 0.28VDC for 3 continuous minutes while the chiller was running.
This feature verifies the operation of the Stall transducer and the Condenser transducer. Since
both transducers are measuring essentially the same pressure, both outputs should be within
the specified tolerance. This message must be manually cleared. It will be displayed until the
transducer outputs are within the acceptable range of each other and the WARNING RESET key in
SERVICE access level.
While this message is displayed, the Variable Geometry Diffuser (VGD) is driven to the full open
position and held there until this warning is manually cleared. When cleared, the VGD returns
normal operation.
Warning – Conditions Override VGD
An extreme stall condition has been detected while the chiller was running. An extreme stall
condition exists when the Stall Detector Voltage (output of the Stall Detector Board) exceeds twice
the High Limit setpoint for the duration programmed in the Extreme Stall Duration Setpoint (10 to
20 minutes). While this message is displayed, the compressor Variable Geometry Diffuser (VGD) is
driven to the full open position and held there until the message is manually cleared. This protects
the VGD ring from possible damage from an extreme stall condition. This message can be cleared
after the Stall Detector Voltage returns to less than two times the High Limit Setpoint and the
WARNING RESET key is pressed in SERVICE access level.
The extreme stall condition is not checked under the following conditions:
• While the VGD is in manual control mode.
• While the VGD is fully closed (VGD Limit Switch closed).
• While the Pre-Rotation Vanes position is greater than the PRV VGD INHIBIT Setpoint.
194 YK-EP Style B Centrifugal Chiller