York YK-EP Operation And Maintenance Manual page 151

Table 145: Programmable
Button Access level
Quick Ramp
Current Service
Threshold
Quick
Pulldown
Service
Setpoint
Offset
Quick Start
Admin
Mode
YK-EP Style B Centrifugal Chiller
Description
This setpoint sets the motor current threshold where the VSD speed
command ramp rate changes. At or below this threshold the speed
command ramp is 4X of standard control. Over this threshold, the
ramp rate is 2X of standard control until it hits the standard current
limiting over 80% FLA. Higher current thresholds can result in faster
pulldown times. However, setting this value too high can result in
slower pulldown times due to hitting the current limit sooner on
pulldown. (20% to 80% FLA; default 50%)
This setpoint sets the Leaving Chilled Liquid Temperature at which
the control transitions from Quick Start mode to normal operation.
It is entered in the form of an offset above the active Leaving Chilled
Liquid Temperature (LCHLT) Setpoint. Once the Leaving Chilled
Liquid Temperature falls below the Active LCHLT Setpoint plus Quick
Pulldown Setpoint Offset, PRV (Quick Restart) and speed control
(Quick Restart and Quick Normal Start) revert to normal automatic
control. Lower values of this offset result in faster pulldown times
but can result in overshoot of the LCHLT Setpoint. Setting the value
to its minimum of 0 results in the fastest pulldown time but nearly
always results in setpoint overshoot. Depending upon how close the
Low Chilled Liquid Temperature shutdown threshold is to the LCHLT
Setpoint, this could result in a LOW CHILLED LIQUID TEMPERATURE
cycling shutdown. (0°F to 10°F; default 5°F).
The Leaving Chilled Liquid Temperature and setpoint is shown on
the QUICK START Screen for reference. This setpoint sets one of
the two setpoints that determine when the control transitions from
Quick Start mode to normal operation. The other is the Pulldown
Override Time below.
This setpoint is used to Enable and Disable the Quick Start feature.
It can only be Enabled when the Motor Drive Type Setpoint is set
to VSD or MVVSD and the Motor Communications Protocol is set to
Modbus.
The default is Disabled. Quick Start can only be enabled using an
ADMIN password. When logged in at ADMIN access level, a QUICK
START key will appear on the SETPOINTS Screen. Pressing this key
will navigate to the QUICK START Screen where this setpoint is used
to enable/disable the feature.
Quick Start can be Disabled when logged in at SERVICE access level.
However, once Disabled, it requires an ADMIN password to enable
it again, as explained above. Quick Start mode will be automatically
disabled when any of the following occur: The Motor Drive Type
is changed to something other than VSD or MVVSD, or the Motor
Communications Protocol is changed to YORK.
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