York YST Operation Manual page 63

FORM 160.67-O1
ISSUE DATE: 4/1/2015
Capacity Control – hgv
Displays the present Capacity Ratchet Mode Selector
output signal for controlling the Hot Gas Bypass Valve.
On startup after the chiller is running at or above the
minimum rated speed and the turbine stabilization de-
lay has elapsed, when the selector is displaying Hot
Gas, this output will be equal to the HGV Ramp out-
put. As the system is pulled down to design conditions,
if the Leaving Chilled Liquid temperature Controller
becomes Active and begins to control this output, the
HSR will select the higher of this signal and the HGV
Ramp output in order to maintain the leaving chilled
liquid temperature at setpoint.
Speed Setpoint
Displays the present setpoint of the Governor (Speed
Control) PID Controller. This setpoint is automati-
cally controlled by the chiller sequencing logic dur-
ing startup and shutdown and by the capacity controls
logic while SYSTEM RUN is displayed. The Gover-
nor Valve output displayed will increase to open the
pneumatically actuated governor valve on the turbine
if the Turbine Speed is below this setpoint. The Slow
Roll, Min Rated, and Rated tuning values entered on
the PID Setup Screen 2 determine the response time of
the Speed Control PID Controller.
Turbine Speed
Displays the highest of the two speed input signals
sensed by two magnetic pickups that monitor a toothed
gear installed on the turbine shaft.
governor valve
Displays the present control signal being sent to the
analog output used to control the I/P transducer on the
pneumatically actuated governor valve. The data field
below the output display shows the Auto/Manual status
of the Speed Setpoint as presently selected on the Auto/
Manual Screen.
hot gas bypass
Displays the present control signal being sent to the
analog output used to control Hot Gas Bypass Valve
actuator. The data field below the output display shows
the Auto/Manual status of the Hot Gas Bypass as pres-
ently selected on the Auto/Manual Screen.
JOHNSON CONTROLS
SECTION 2 - OPTIVIEW CONTROL CENTER INTRODUCTION
pre-rotation vanes
Displays the present control signal being sent to the
PRV positioning logic used to control the Open/Close
digital outputs connected to the PRV actuator. The data
field below the output display shows the Auto/Manual
status of the Pre-Rotation Vanes as presently selected
on the Auto/Manual Screen.
prograMMable
none
navigaTion
home
Access Level Required: VIEW
Causes an instant return to the Home Screen.
pid Setup 1
Access Level Required: VIEW
Moves to a subscreen that allows programming of the
tuning parameters for the Leaving Chilled Liquid Tem-
perature, Evaporator Pressure, Condenser Pressure,
Hotwell Level, and Subcooler Level PID controllers.
pid Setup 2
Access Level Required: VIEW
Moves to a sub-screen that allows programming of the
tuning parameters for the Governor (Slow Roll), Gov-
ernor (Min Rated), Governor (Rated), Governor Valve
Position Limit, Horsepower Limit PID controllers.
auto/Manual
Access Level Required: SERVICE
Moves to a sub-screen that allows the operator to man-
ually control any of the capacity control devices. The
programmable Anti-Surge limits are also accessible
from this screen.
Setpoints
Access Level Required: VIEW
Moves to a sub-screen that allows programming of var-
ious parameters pertinent to the operation of the capac-
ity controls. It is also the gateway to Capacity Control
Setpoints Screen 2.
2
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