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SECTION 30 - QUICK START
Quick Start Mode will be automatically disabled when
any of the following occur:
• The Motor Drive Type is changed to something
other than VSD or MVVSD.
• The Motor Communications Protocol is changed
to YORK.
• The Heat Pump Duty (if enabled) Operational
setpoint is set to Heating Mode.
Quick Pulldown Setpoint Offset
(0°F to 10°F; default 5°F)
This setpoint sets the Leaving Chilled Liquid Tem-
perature at which the control transitions from Quick
Start Mode to normal operation. It is entered in the
form of an offset above the active Leaving Chilled
Liquid Temperature (LCHLT) setpoint. Once the leav-
ing chilled liquid temperature falls below the Active
LCHLT setpoint + Quick Pulldown Setpoint Offset,
PRV (Quick Restart) and speed control (Quick Re-
start and Quick Normal Start) revert to normal au-
tomatic control. Lower values of this offset result in
faster pulldown times but can result in overshoot of the
LCHLT setpoint. Setting the value to its minimum of 0
results in the fastest pulldown time but nearly always
results in setpoint overshoot. Depending upon how
close the Low Chilled Liquid Temperature shutdown
threshold is to the LCHLT setpoint, this could result in
a Low Chilled Liquid Temperature cycling shutdown.
The leaving chilled liquid temperature and setpoint is
shown on the QUICK START Screen for reference.
This setpoint sets one of the two setpoints that deter-
mine when the control transitions from Quick Start
Mode to normal operation. The other is the Pulldown
Override Time below.
Pulldown Override Time
0 min to 15 min; default 10 min)
This setpoint is the length of time the PRV is held open
(Quick restart) and the ACC speed (Quick Restart and
Quick Normal Start) is increased on startup if the Quick
Pulldown Setpoint Offset is not reached. This could be
due to hitting current limit during the pulldown. If the
Quick Pulldown Setpoint Offset is not reached in the
Pulldown Override Time, PRV and ACC speed control
will revert back to normal automatic control.
• VSD Start Frequency (60Hz units with quick
start enabled equals 30Hz to 45Hz; default 45Hz)
(50Hz equals 25Hz to 37.5Hz; default 37.5Hz) -
248
This setpoint is the same as shown on the ACC
DETAILS Screen. It can be programmed on either
the ACC Screen or the QUICK START Screen.
It sets the VSD start frequency from which the
speed will ramp from.
• ACC Mapping Enable (0.5°F to 4.0°F; default
1.0°F) - This is the same setpoint as shown on the
ACC DETAILS Screen. It can be programmed
on either the ACC Screen or the QUICK START
Screen. It sets the Delta T needed to be met to en-
able surge mapping and speed reduction initially
on startup.
• Quick Ramp Current Threshold (20% to 80%
FLA; default 50%) - This setpoint sets the motor
current threshold where the VSD speed command
ramp rate changes. At or below this threshold the
speed command ramp is 4X of standard control.
Over this threshold, the ramp rate is 2X of stan-
dard control until it hits the standard current limit-
ing over 80% FLA. Higher current thresholds can
result in faster pulldown times. However, setting
this value too high can result in slower pulldown
times due to hitting the current limit sooner on
pulldown.
• Coastdown Time – When Quick Start is enabled,
the minimum programmable coastdown time for
this setpoint is lowered as follows:
• The shorter the programmed Coastdown Time,
the less time it takes from a shutdown or power
failure until the compressor can be restarted. This
value is programmable from the SETUP Screen.
The actual mechanical Coastdown Time should
be observed while performing several hard stops
(with control panel rocker switch) on the chiller at
various load/head conditions and visually check-
ing when rotation stops. The time period pro-
grammed for the Coastdown Time needs to be
longer than the longest physical time it takes the
compressor rotation to stop.
JCI COMPANY CONFIDENTIAL
ISSUE DATE: 10/25/2019
- Q Compressors from 150 seconds to 60 sec-
onds
- J7 and K7 Compressors from 240 to 150
seconds
- All other Compressors from 150 to 90
seconds
FORM 160.54-M1
JOHNSON CONTROLS
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