Johnson Controls YORK YVAM 0350, Operation & Maintenance Manual

Page: 51 / 162

Capacity control screen
Figure 22: Capacity control screen
This screen displays the pertinent parameters associated with capacity control in relation to Leaving
Chilled Liquid temperature, current and pressure overrides, and anti-surge control. This screen also
provides a means for a service technician to control VGD, speed, and optional hot gas bypass valve
manually for maintenance or service.
Table 33: Display only fields
Field/LED name Description
Evaporator Pressure Displays the pressure in the evaporator.
[Evaporator Pressure]
Override Threshold
Displays the evaporator pressure setpoint below which the low evaporator pressure capacity
control override takes effect.
Condenser Pressure Displays the pressure in the condenser.
[Condenser Pressure]
Override Threshold
Displays the condenser pressure setpoint above which the high condenser pressure capacity
control override takes effect.
Input Current % FLA Displays the percent of useful job full load current presently supplied to the chiller,
determined from the highest of the three-phase Input Currents/(Input Job FLA setting/0.9).
[Input Current % FLA]
Override Threshold
Displays the active input current percent limit, which is the minimum of Local Input Current
Limit, Remote Input Current Limit, and Pulldown Current Limit or BAS (ISN) current limit.
Motor Current % FLA Displays the percentage of maximum motor current delivered to the motor, determined
from the highest of the three phase Motor Currents/Maximum Motor Current Limit.
[Motor Current % FLA]
Override Threshold
Displays the active motor current percent limit, which is a percentage of the minimum of
variable speed drive and motor maximum current limits.
Entering Chilled Liquid Displays the temperature of the chilled liquid as it enters the evaporator.
Leaving Chilled Liquid Displays the temperature of the chilled liquid as it leaves the evaporator.
Active LCHLT setpoint Displays the active temperature setpoint to which the chiller is set to control liquid leaving
the evaporator. The active setpoint is a target to the Local, Remote, or BAS (ISN) LCHLT
programmed setpoint, depending on the control source selected. When the chiller is not
running, the Active setpoint is set to Entering Chilled Liquid Temperature - LCHLT setpoint
Start Offset. When the VSD starts, the Active LCHLT setpoint is ramped to the programmed
LCHLT setpoint at the programmable LCHLT setpoint ramp rate. When the chiller is running,
performing capacity control, any change to the programmed LCHLT setpoint results in a
ramp from the old Active setpoint value to the new LCHLT setpoint value at the programmed
LCHLT setpoint Ramp Rate.
51 YVAM Control Center