Johnson Controls YORK YVAM 0350, Operation & Maintenance Manual

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Automatic temperature shutdown
The Leaving Chilled Liquid Temperature Cycling Offset, Shutdown setting on the panel can be
programed to set the temperature below the LCHLT setpoint at which the chiller automatically
cycles off when the load is less than the chiller minimum capability. 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 (-17.2°C to 17.8°C). However, the actual shutdown temperature is never
calculated to lower than 36°F (2.2°C) for water, 34°F (1.1°C) for water with Smart Freeze enabled, or
6°F (-14.4) for 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 equal to half the
programmed LCHLT Setpoint Ramp Rate. This provides time for the chiller to change temperature
without shutting down first.
Automatic temperature restart
The Leaving Chilled Liquid Temperature Cycling Offset, Restart setting on the panel can be
programed to set the temperature above the LCHLT setpoint at which the chiller automatically
restarts after a low LCHLT shutdown, as described previously. 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 (-17.8°C to 21.1°C). However, the restart temperature is never calculated above
80°F (26.7°C). 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 6: 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
25 YVAM Control Center