York YST Operation Manual page 61

FORM 160.67-O1
ISSUE DATE: 4/1/2015
override limit - Condenser pressure
Displays the present refrigerant pressure in the con-
denser.
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 tur-
bine.
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 Team 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 Yellow if this control-
ler 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 speed reduction
and vane closure based on the head pressure differen-
tial (condenser minus evaporator pressure). The out-
put data fields display the present calculated minimum
speed and vane control signals.
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.
JOHNSON CONTROLS
SECTION 2 - OPTIVIEW CONTROL CENTER INTRODUCTION
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.
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 - high head Min Speed
Displays the present High Head Min Speed setpoint
that is entered on the Auto/Manual Screen. This is the
minimum speed setpoint allowed when the head is
equal to the High Head Pressure Delta setpoint.
anti-Surge - low head Min Speed
Displays the present Low Head Min Speed setpoint
that is entered on the Auto/Manual Screen. This is the
minimum speed setpoint allowed when the head is
equal to the Low Head Pressure Delta setpoint.
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
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