York OPTIVIEW Operation Manual page 25

FORM 160.78-O2
ISSUE DATE: 5/22/2017
Leaving Chilled Liquid Temperature Cycling
Offset - Shutdown
Access Level Required: OPERATOR
This value allows the user to specify the Leaving
Chilled Liquid Temperature at which the chiller will
shut down on a LEAVING CHILLED LIQUID – LOW
TEMPERATURE cycling shutdown. This is done by
defining an offset below the Leaving Chilled Liquid
Temperature setpoint. It is programmable over a range
of 1°F to 64°F below the setpoint, to a minimum cut-
out of 36°F (water), 34°F (water with Smart Freeze
enabled) or 6°F (brine). Anytime the Leaving Chilled
Liquid Temperature setpoint is decreased, the shut-
down 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 leaving
chilled liquid temperature active setpoint minus offset
at a rate = 1/2 the programmed LCHLT Setpoint Ramp
Rate.
The offset being used is displayed as Effective Off-
set in the upper right area of the display. Usually, the
Offset used is the same as the value programmed for
the SHUTDOWN setpoint. However, the Offset be-
ing used will automatically change based on the val-
ues programmed for the LEAVING CHILLED LIQ-
UID TEMPERATURE setpoint and the SHUTDOWN
setpoint, to prevent the leaving chilled liquid tempera-
ture from going below the minimum allowed value:
36ºF (water), 34ºF (water with smart freeze enabled)
or 6ºF (brine). For example, if the leaving Chilled Liq-
uid Temperature setpoint is set to 45ºF (water) and the
SHUTDOWN setpoint is set to 4ºF, the Effective Off-
set is displayed as 4ºF. If the leaving setpoint is low-
ered to 38ºF, the Effective Offset will change to 2ºF. If
the leaving chilled setpoint is raised back to 45ºF, the
Effective Offset will revert back to the SHUTDOWN
setpoint.
JOHNSON CONTROLS
SECTION 2 - OPTIVIEW CONTROL CENTER INTRODUCTION
Leaving Chilled Liquid Temperature Cycling
Offset - Restart
Access Level Required: OPERATOR
This value allows the user to specify the Leaving
Chilled Liquid Temperature at which the chiller will
restart after a shutdown on a LEAVING CHILLED
LIQUID – LOW TEMPERATURE cycling shutdown.
This is done by defining an offset above the Leaving
Chilled Liquid Temperature setpoint. It is program-
mable over a range of 0°F to 70°F above the setpoint,
to a maximum restart value of 80°F. The chiller will
automatically restart when this temperature is reached.
This setpoint can be used to reduce chiller cycling by
delaying the chiller restart until the cooling load has
increased.
Refrigerant (Enabled / Disabled)
Access Level Required: SERVICE
The Evaporator Refrigerant Sensor must be enabled
via this toggle before the system will utilize the new,
enhanced resolution input. Service Technicians refer to
YORK YMC Service Manual (Form 160.78-M2).
2
Smart Freeze (Off / On)
Access Level Required: SERVICE
This value is only available if the chiller is not in Brine
mode. It allows the user to enable the Smart Freeze
Point Operation which allows the chiller to run clos-
er to the freeze point without shutting down. Service
Technicians refer to YORK YMC
(Form 160.78-M2).
Brine Low Evaporator Cutout
Access Level Required: SERVICE
This value is only available in Brine mode. It allows
the user to specify the Evaporator Pressure at which a
safety shutdown is initiated. Service Technicians refer
to YORK YMC Service Manual (Form 160.78-M2).
2
NAVIGATION
Home
Causes an instant return to the Home Screen.
2
Service Manual
2
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