ramped from this value to the programmed LCHLT Setpoint at the programmable LCHLT Setpoint
Ramp Rate (default 0.1°F/second). This keeps the chiller from undershooting setpoint excessively
during pulldown. Any time the programmed setpoint is changed during operation, the active
setpoint is ramped to the new value at this rate.
Automatic temperature shutdown
The temperature below the LCHLT setpoint at which the chiller is desired to automatically cycle off
when load is less than the chiller minimum capability is programmed from the panel as Leaving
Chilled Liquid Temperature Cycling Offset; Shutdown. This setting defines the temperature offset
below the LCHLT setpoint where shutdown is expected. It is programmable over a range of 1°F to
64°F. However the actual shutdown temperature will never be calculated to lower than 36°F (water),
34°F (water with Smart Freeze enabled) or 6°F (brine). Anytime the LCHLT setpoint is decreased, the
shutdown threshold decreases to the new LCHLT active setpoint minus offset at a rate equal to the
programmed LCHLT Setpoint Ramp Rate. Anytime the Leaving Chilled Liquid Temperature setpoint
is increased, the shutdown threshold increases to the new LCHLT active setpoint minus offset at a
rate = 1/2 the programmed LCHLT Setpoint Ramp Rate. This allows time for the chiller to change
temperature without shutting down first.
Automatic temperature restart
The temperature above the LCHLT setpoint at which the chiller is desired to automatically restart
after a low LCHLT shutdown, as above, is programmed from the panel as Leaving Chilled Liquid
Temperature Cycling Offset; Restart. This setting defines the temperature offset above the LCHLT
setpoint where automatic restart is expected. It is programmable over a range of 0°F to 70°F.
However, the restart temperature will never be calculated above 80°F. This setpoint can be used to
reduce chiller cycling by delaying the chiller restart until the cooling load has increased sufficiently.
Operator setpoints quick reference
The most common Operator level setpoints can be found on the Setpoints screen or the following
screens:
Table 5: Common setpoint locations
Setpoint Screen
Leaving Chilled Liquid Temperature: Evaporator
Shutdown Temperature Offset: Evaporator
Restart Temperature Offset: Evaporator
Local Input Current Limit: VSD
Pulldown Demand Limit: VSD
Pulldown Demand Time: VSD
Control Source: Setpoints > Setup > Operations
Head Pressure Setpoint (When The Feature Is
Enabled)
Condenser > Head Pressure > Control
YMC
2
Mod B with OptiView
™
Control Center
22
To Next Page
Loading...
Need help?
General
