FORM 155.21-O1 (615)
41
JOHNSON CONTROLS
Schedule Setpoints
N/A
Pulldown Setpoints
Ramp Down Interval Timer (Soft Shutdown)
Access Level required:
OPERATOR
This setpoint defines the time interval for the control to
use to ramp the steam/hot water control valve from full
open to the minimum load setpoint, prior to shutdown
of the chiller upon a soft shutdown command. This time
is referenced to a 100% open valve position, so actual
ramp down time at other valve positions is a propor-
tion of this maximum interval. Actual ramp down time
is determined by the following: Ramp Down Interval
Timer x (Valve position at onset - Low Unload Limit
setpoint) / (100- Low Unload Setpoint). Once the valve
position reaches the minimum load setpoint, the unit is
shutdown from cooling sequence. This setpoint should
be set as required to avoid shocks in the site steam sup-
ply system.
RANGE: 0 min. - 60 min.
DEFAULT: 0 min.
Pull Down Interval Timer
Access Level required:
OPERATOR
This setpoint defines the duration of the pulldown
process. Pulldown is executed on initial startup. The
pulldown process saves energy and relieves the chiller
startup transient on the site heat supply by limiting the
steam/hot water control valve opening to a controlled
linear ramp when the machine is starting. The steam/hot
water control valve maximum opening position is lim-
ited by the prevailing pulldown demand limit position.
This position is an increasing ramp from the Pulldown
Loading Start Setpoint position to the Pulldown Load
-
ing Stop Setpoint position over the Pulldown Interval
Time.
RANGE: 0 min. - 255 min.
DEFAULT: 0 min.
Pulldown Loading Start Setpoint
Access Level required:
OPERATOR
This setpoint defines the control valve open position
limit at the beginning of the pulldown process.
RANGE: 10% - 30%
DEFAULT: 10%
Pulldown Loading Stop Setpoint
Access Level required:
OPERATOR
This setpoint defines the control valve open position
limit at the end of the pulldown process.
RANGE: 20% - 100%
DEFAULT: 10%
Current Valve Opening = [(Pulldown loading stop
setpoint - Pulldown loading start setpoint)*(Time
elapsed of the pull down process / Pulldown interval
timer)] + Pulldown loading start setpoint.
Access Level Required:
VIEW
Generates
Setpoints
print report.
NAVIGATION
Home
Causes an instant return to the Home Screen.
Operation
Selects operational setpoints for viewing.
Schedule
Selects Schedule setpoints for viewing.
Pulldown
Selects Pulldown setpoints for viewing.
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