York YST Operation Manual page 27

FORM 160.67-O1
ISSUE DATE: 4/1/2015
leaving Chilled liquid Temperature Setpoints
- Shutdown
Displays the Leaving Chilled Liquid Temperature at
which the chiller will shut down to avoid over-cooling
the building. By default this value is 4°F below the
Leaving Chilled Setpoint.
leaving Chilled liquid Temperature Setpoints
– restart
Displays the Leaving Chilled Liquid Temperature at
which the chiller will restart after it has shut down due to
over-cooling temperature. By default, the chiller will re-
start at the Leaving Chilled Liquid Temperature Setpoint.
prograMMable
local leaving Chilled liquid Temperature -
range
Access Level Required: OPERATOR
This is the range over which an analog (0-20mA,
4-20mA, 0-10VDC or 2-10VDC) in Analog Remote
Mode or a digital signal (PWM) in Digital remote
mode can reset the Leaving Chilled Liquid Tempera-
ture setpoint above the operator programmed Base
Setpoint (see below). Programmable as either 10°F or
20°F, with a default of 20°F, it is added to the Base
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
value is 45°F, then the remote device can set the Leav-
ing Chilled Liquid Temperature setpoint over the range
45.0° - 55.0°F.
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 (see below) is enabled, the range is 36.0°F to
70.0°F (water). A remote device can provide an ana-
log signal (0-20mA, 4-20mA, 0-10VDC or 2-10VDC)
in Analog Remote mode, or PWM signal in Digital
Remote mode that changes the setpoint by creating
an offset above the operator programmed Base Leav-
ing Chilled Liquid Temperature setpoint. This offset
may be defined up to 10.0°F or 20.0°F above the Base
JOHNSON CONTROLS
SECTION 2 - OPTIVIEW CONTROL CENTER INTRODUCTION
setpoint (see the Remote Leaving Chilled Liquid Tem-
perature Setpoint Range description above). Addition-
ally, MicroGateway (in ISN 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 Base setpoint value, but rather
is the setpoint value itself.
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
cutout of 36°F (water), 34°F (water with Smart Freeze
enabled) or 6°F (brine). It establishes the minimum al-
lowable temperature for the Leaving Chilled Liquid
Temperature and prevents over-cooling of the build-
ing. Anytime the Leaving Chilled Liquid Temperature
setpoint is increased, the shutdown threshold is 36.0°F
(water) or 6.0°F (brine) for the next ten (10) minutes.
If Smart Freeze (see below) is enabled, the threshold is
34.0°F for the next 10 minutes. After ten (10) minutes
have elapsed, the shutdown threshold becomes the pro-
grammed setpoint value.
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 shut-
down. This is done by defining an offset above the
Leaving Chilled Liquid Temperature setpoint. It is
programmable 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.
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