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SECTION 30 - QUICK START
FORM 160.54-M1
ISSUE DATE: 10/25/2019
JOHNSON CONTROLS
JCI COMPANY CONFIDENTIAL
30
OPERATION
When Quick Start Mode is enabled, there are several
operational enhancements common to both Quick Re-
start and Quick Normal Start to decrease time between
starts as follows:
• The Coastdown time can be shortened using the
Coastdown Time setpoint. The shortest possible
time for the Coastdown Time setpoint should
be determined using the procedure above under
Coastdown Time setpoint.
• The OIL - LOW TEMPERATURE DIFFEREN-
TIAL threshold is decreased to 10°F (from 30 or
40, depending on conditions) for 15 minutes after
the last shutdown (the timer begins when the run
signal is removed).
• The Oil Heater is controlled to maintain a mini-
mum oil temperature, ensuring it is warm enough
to allow a restart as follows: While the oil pump is
running, if oil temperature is less than 100°F, the
Oil Heater is turned ON until it reaches greater than
105°F whereupon it is turned OFF. In order for this
function to operate, a wiring change is required to
the Oil Heater wiring as described below.
• The Hot gas bypass Valve is positioned to the
Maximum Open setpoint value during Soft Shut-
down, Coastdown and while not running. It re-
turns to normal control (closed) when the Run
signal is ENABLED.
• The PRV open/close status switch does not have
to be closed in order to start.
Quick Restart
Whenever the chiller shuts down, for whatever reason,
the following will occur in preparation for a Quick Re-
start: During the Coastdown period and for 30 seconds
after the end of Coastdown, the PRV and Variable Ori-
fice positions are held in place, a precharge command
is sent to the VSD, the chilled Liquid Pump contacts
TB2-44/45 are maintained closed and the Oil Pump
continues to run (target oil pressure 45 psid).
When Coastdown has completed (and for 30 seconds
thereafter), if the following conditions are met, a run
command is sent to the VSD and the Quick Pulldown
begins. No Pre-lube occurs.
• Oil Pressure more than 25 psid
• VSD has completed Precharge
• Chiller start signal (local or remote) is present
• No faults/inhibits present
•
Chilled liquid flow switch is closed
Since there is no Pre-lube, the Auto-zeroing that nor-
mally occurs between the Oil Pressure Transducers
during Pre-lube, does not occur. The offset calculation
from the last Quick Normal Start is used. The level
control preset (for the duration set by the Valve Preset
Time setpoint) does not take place.
When the run command is sent to the VSD, the chiller
enters System run and the Quick Pulldown begins. The
QUICK PULLDOWN IN EFFECT LED on the QUICK
START Screen illuminates while the Quick Pulldown is
in effect. The Level Control begins ramping immediate-
ly, rather than waiting for 3 minutes after entering Sys-
tem run, as it does in normal operation. The Oil Pump
continues to use the Target Oil Pressure of 45 psid for the
first 15 seconds into run, then reverts to the programmed
setpoint value. The speed command programmed as the
VSD Start Frequency setpoint is sent to the VSD. The
speed will ramp up to maximum frequency from this
point at 4X the standard control until it reaches the cur-
rent set as the Quick Ramp Current Threshold setpoint
(20-80% FLA), whereupon it ramps at 2X standard con-
trol until it reaches the standard current limiting over
80% FLA, whereupon it ramps at standard rate. A con-
tinuous open signal is applied to the PRV.
The continuous open signal to the PRV and the quick
VSD speed ramping will continue until either the
Leaving Chilled Liquid Temperature decreases to the
temperature set by the Quick Pulldown Setpoint Offset
(0 to10°F) setpoint or the Pulldown Override Time (0
to 15 min) setpoint has elapsed, whereupon all VSD
speed control and PRV control returns to standard.
In order for a Quick Restart to be performed after a
power failure, the power failure duration must be no
longer than about 60 seconds. Data centers can gener-
ally guarantee stable generator power to be available
15 seconds or less following a power failure. Longer
power failures will result in a Quick Start (see below)
rather than a Quick Restart.
If the criteria for a Quick Restart above is not met with-
in 30 seconds after coastdown has completed, the fol-
lowing control returns to standard control:
• Chilled Liquid Pump control returns to standard
• PRV control returns to standard