York YST, Operation Manual

Page: 56 / 164

JOHNSON CONTROLS
56
FORM 160.67-O1
ISSUE DATE: 4/1/2015
SECTION 2 - OPTIVIEW CONTROL CENTER INTRODUCTION
CapaCiTY ConTrolS SCreen-fixed Speed Mode
LD09261
figure 21 - CapaCiTY ConTrolS SCreen-fixed Speed Mode
noTe: OptiView
™
Control Center Screens shown may NOT represent the exact screens according to the software version utilized.
overvieW
This screen appears when MSSP7-Speed Control
Mode on Capacity Control Setpoints Screen 1 is set for
Fixed. The fixed speed mode would likely only be used
in plants where the condensing water is always at a
high temperature so that speed reduction would not be
possible due to the high system pressure differential.
This screen is a detailed view of the capacity control
system including various override and anti-surge con-
trol setpoints and parameters. It is also the gateway to
screens for entering the tuning parameters of the vari-
ous PID controllers and other setpoints pertinent to the
operation of the capacity controls. The Auto/Manual
Screen is also accessible from this screen.
diSplaY onlY
graphics and animation
The arrows on the interconnecting lines indicate the
logical direction of signal flow between the controlling
devices. An HSR (High Select Relay) will select the
higher of the two signals entering it and pass it on to
the next device. An LSR (Low Select Relay) will select
the lower of the two signals entering it and pass it on to
the next device. The line within the relay will toggle to
show which input is currently being selected.
override limit box
This box displays parameters pertinent to the over-
ride limiting controls that take control of the capacity
control devices during off design operation in order to
prevent unsafe operation and prevent the chiller from
shutting down.
override limit - evaporator pressure Setpoint
Displays the present setpoint of the Evaporator Pres-
sure PID controller that is entered on PID Setup Screen
1. If the evaporator pressure falls below this value, the
output of this block will decrease below 100%. The
text color changes to Red if this controller is active.
override limit - evaporator pressure
Displays the present refrigerant pressure in the evapo-
rator.
override limit - Condenser pressure Setpoint
Displays the present setpoint of the Condenser Pres-
sure PID controller that is entered on PID Setup Screen
1. If the condenser pressure 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 - Condenser pressure
Displays the present refrigerant pressure in the con-
denser.