York YST Operation Manual page 57

FORM 160.67-O1
ISSUE DATE: 4/1/2015
override limit - horsepower limit Setpoint
This is displayed if MSSP8-Power Limiting Mode on
Capacity Control Setpoints Screen 1 is set for Horse-
power. It displays the present setpoint of the Horse-
power Limit PID controller. If the calculated horse-
power rises above this value, the output of this block
will decrease below 100%. The text color changes to
Red if this controller is active.
override limit - horsepower
Displays the calculated horsepower output of the turbine.
override limit - governor position Setpoint
This is displayed if MSSP8-Power Limiting Mode on
Capacity Control Setpoints Screen 1 is set for Position.
It displays the present setpoint of the Gov Valve Posi-
tion Limit PID controller that is entered on PID Setup
Screen 2. This mode is only used when the Turbine
First Stage Steam Pressure Transmitter is not present.
In this case, the only available means to prevent the
turbine from producing too much power is to monitor
the Governor Valve output at normal full load condi-
tions and then enter this percent as the setpoint for the
position-limiting controller. If the output signal con-
trolling the Governor Valve I/P Transducer rises above
this value, the output of this block will decrease below
100%. The text color changes to Red if this controller
is active.
override limit - governor valve
Displays the present output signal controlling the Gov-
ernor Valve I/P Transducer.
anti-Surge box
This box displays parameters pertinent to the anti-surge
controls that limit the amount of vane closure based on
the head pressure differential (condenser minus evapo-
rator pressure). The output data field displays the pres-
ent calculated minimum vane control signal.
anti-Surge - high head Min prv
Displays the present High Head Min PRV setpoint
that is entered on the Auto/Manual Screen. This is the
minimum PRV control signal allowed when the head is
equal to the High Head Pressure Delta setpoint.
anti-Surge - low head Min prv
Displays the present Low Head Min PRV setpoint
that is entered on the Auto/Manual Screen. This is the
minimum PRV control signal allowed when the head is
equal to the Low Head Pressure Delta setpoint.
JOHNSON CONTROLS
SECTION 2 - OPTIVIEW CONTROL CENTER INTRODUCTION
anti-Surge - high head press delta
Displays the present High Head Pressure Delta setpoint
that is entered on the Auto/Manual Screen. This is the
maximum head that the chiller will likely see in nor-
mal operation. The output data field will show the High
Head Min PRV value when the Head Pressure is at this
value.
anti-Surge - low head press delta
Displays the present Low Head Pressure Delta setpoint
that is entered on the Auto/Manual Screen. This is the
minimum head that the chiller will likely see in normal
operation while running at or above the minimum rated
speed. The output data field will show the Low Head
Min PRV value when the Head Pressure is at this value.
anti-Surge - head pressure
Displays the present result of the condenser refrigerant
pressure minus the evaporator refrigerant pressure.
Temperature Control box
This box displays parameters pertinent to the Leaving
Chilled Liquid Controller used to maintain the liquid
temperature at the setpoint shown. The output dis-
played will decrease to unload the chiller if the Leav-
ing Chilled Liquid Temperature is below the Setpoint.
The response time of the controller is determined by
the tuning entered on the PID Setup Screen 1. The data
field above the output display shows the Inactive or
Active status of the controller. The controller is Inac-
tive (yellow text) during shutdown and ramp up to rat-
ed speed with its output signal equal to the present PRV
Ramp signal. It becomes Active (green text) when the
vane ramp signal is at 97% or the leaving chilled liq-
uid temperature decreases to within 2 °F of the present
setpoint. It is also Inactive if any override controller is
active, in which case its' output is equal to the override
block output. It becomes Active after the override con-
troller is no longer controlling and the TDSP10-Temp
Control Override Transfer Delay shown on the Capac-
ity Control Setpoints Screen 1 has elapsed.
Temperature Control - Setpoint
Displays the present Leaving Chilled Liquid Tempera-
ture Setpoint used to control the chiller. This may be
the Local Setpoint entered on the Setpoints Screen or
the Remote Setpoint if being controlled by a remote
signal.
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