York YST Operation Manual page 73

FORM 160.67-O1
ISSUE DATE: 4/1/2015
decrease Key
Access Level Required: SERVICE
This key decreases the Manual control signal 1% each
time it is pressed.
Set Key
Access Level Required: SERVICE
This key displays a pop-up window which allows
the operator to enter a value from 0-100%. When
the "" key is pressed, the pop-up window
disappears and the manual signal ramps to the
value entered at 2%/second.
overspeed Test Key (no/Yes)
Access Level Required: SERVICE
Only a qualified YORK or turbine manu-
facturer Service Technician should per-
form this test.
When the operator pushes this key, the message
WARNINg - MECHANICAL OVERSPEED TEST
IN PROgRESS is displayed and the key data field
changes to Yes. During the test, the software overspeed
shutdown at the SSP8-Overspeed Shutdown setpoint
shown on the Alarm/Shutdown Setpoints Screen is
disabled to allow the operator to manually increase the
Speed Setpoint at a fixed 1%/sec rate up to the SSP4-
Overspeed Test Limit shown on the Speed Setpoints
Screen. The mechanical trip mechanism on the turbine
should trip before SSP4-Overspeed Test Limit speed
is reached and the message TURBINE MECHANI-
CAL TRIP displayed. If the turbine does not trip and
the speed exceeds the SSP4-Overspeed Test Limit
setpoint for 2 seconds, the chiller will be tripped and
MECHANICAL OVERSPEED TEST FAILURE
will be displayed.
JOHNSON CONTROLS
SECTION 2 - OPTIVIEW CONTROL CENTER INTRODUCTION
If the key is pushed prior to the mechanical trip and
the speed is below the SSP8-Overspeed Shutdown
setpoint,, the status bar is changes back to the normal
operating message, the software overspeed shutdown
is reactivated. When the speed setpoint is put in the
Auto mode, the speed is ramped down to the present
rated speed setpoint.
If the button is pushed prior to the mechanical trip and
the speed is above the SSP8-Overspeed Shutdown
setpoint, the turbine will be tripped immediately and
the message TURBINE OVERSPEED TRIP will be
displayed.
If the turbine mechanical trip functions properly and
the chiller is tripped, the overspeed test logic is inac-
tivated and the key data field changes to No after no
rotation has been detected for 35 seconds.
navigaTion
home
Access Level Required: VIEW
Causes an instant return to the Home Screen.
Capacity Controls
Access Level Required: VIEW
Causes an instant return to the Capacity Controls
Screen.
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