JOHNSON CONTROLS
97
SECTION 2 – OPTIVIEW CONTROL CENTER
FORM 160.79-O3
ISSUE DATE: 11/09/2018
2
PROGRAMMABLE
Local Leaving Chilled Liquid Temperature -
Setpoint
Access Level Required: OPERATOR
This value allows the user to define the Leaving
Chilled Liquid Temperature that is to be maintained by
the chiller. It is programmable over the range of 38.0°F
to 70.0°F (water) or 10.0°F to 70.0°F (brine).
If Smart Freeze is enabled, the range is 36.0°F to
70.0°F (water). A remote device can provide an analog
signal (0-20 mA, 4-20 mA, 0-10 VDC or 2-10 VDC)
in Analog Remote mode, or PWM signal in Digital
Remote mode that changes the setpoint by creating an
offset above the operator programmed Local Leaving
Chilled Liquid Temperature setpoint. This offset may
be defined between 10.0°F and 40.0°F above the Lo-
cal setpoint (see the Remote Leaving Chilled Liquid
Temperature Setpoint Range description). Addition-
ally, an SC-EQ in ISN (BAS) Remote mode can define
the setpoint through a serial data stream. In this case,
the incoming setpoint is not an offset that is applied to
the locally programmed setpoint value, but rather is the
setpoint value itself.
Local Leaving Chilled Liquid Temperature -
Range
Access Level Required: OPERATOR
This is the range over which an analog signal (0-20
mA, 4-20 mA, 0-10 VDC or 2-10 VDC) in Analog Re-
mote Mode or a digital signal (PWM) in Digital remote
mode can reset the Leaving Chilled Liquid Temperature
setpoint above the operator programmed Base Setpoint
(see below). Programmable between 10°F and 40°F,
with a default of 10°F, it is added to the Local Setpoint
value to create a range over which the remote device
can reset the setpoint. For example, if this setpoint is
programmed for 10°F and the operator programmed
Local value is 45°F, then the remote device can set the
Leaving Chilled Liquid Temperature setpoint over the
range 45.0°F - 55.0°F.
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 70°F below the setpoint, to a minimum cutout
of 36°F (water) or 6°F (brine). It establishes the mini-
mum allowed temperature for the Leaving Chilled Liq-
uid Temperature and prevents overcooling of the build-
ing. Anytime the Leaving Chilled Liquid Temperature
setpoint is increased, the shutdown threshold is ramped
from the current setpoint to the new setpoint at the rate
of 0.1°F per second to prevent the chiller from imme-
diately tripping on low water temperature.
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 programma-
ble over a range of 0°F to X°F where X = 80 minus the
LCHLT Setpoint. 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.
Local Chiller Current Limit
Access Level required: OPERATOR
Allows the user to specify the maximum allowed Chill-
er Current while running. Adjustable between 30% and
100%; default = 100%.
Lead Compressor Pulldown Demand Limit
Access Level Required: OPERATOR
Allows the user to specify the maximum allowed Chill-
er Current during the Lead Compressor Chiller Pull-
down Period. The Chiller Pulldown Period is in effect
from the instant the chiller enters “System Run” until
the Leaving Chilled liquid temperature is within 2ºF
of the Leaving Chilled Liquid Temperature Setpoint
or the Lead Compressor Pulldown Time has expired.
Adjustable between 30% and 100%; default = 100%.
Lead Compressor Pulldown Time
Access Level Required: OPERATOR
Allows the user to specify the amount of time that the
Lead Compressor Pulldown Demand Limit will be in
effect. Adjustable between 0 and 255 minutes; default
= 0 minutes.
