Compressor Shutdown - York OPTIVIEW YD Series Manual

FORM 160.79-O3
ISSUE DATE: 11/09/2018
After the Lead Compressor Pulldown Time Setpoint
has elapsed, the chiller current limit will be limited to
the value programmed for the Chiller Current Limit
Setpoint. As in previous software versions, this setpoint
is applied to the total chiller current (30% to 100% of
the Chiller Full Load Amps). For example, if the Chill-
er FLA is 1600 Amps, the FLA of each motor is 800
Amps. If this setpoint is set to 70%, the Chiller Cur-
rent would be limited to 1120 Amps. If both compres-
sors are running, each would be limited to 560 amps. If
only one motor is running, the motor would be allowed
to operate all the way up to its full load amps of 800
Amps, because the total chiller current is being limited
to 1120 Amps.
Compressor Lockout
The COMPRESSOR LOCKOUT Setpoint, available
on the Capacity Compressor Cycling Screen, can be
used to lockout either compressor. The designated
compressor will not be permitted to run. This feature is
useful when it is desired to perform service on a com-
pressor.
A single compressor can be locked out while both com-
pressors are running, without shutting down the entire
chiller. A soft shutdown will be performed on the run-
ning compressor selected for lockout and its status is
changed to "Lag" (if it is not the lag compressor al-
ready). Upon completion of Coastdown, the compres-
sor will remained locked out until the lockout is re-
leased. If there is only one compressor running and it is
the one targeted for lockout, the user will have to either
shutdown the entire chiller and then lockout the desired
compressor or bring the other compressor on line and
then lockout the desired one. In previous software ver-
sions, a compressor can only be locked out only while
it is shutdown.
The following Safety or Cycling Conditions on a
Locked-out compressor will not cause the other com-
pressor to shutdown. In previous software versions,
these cycling and safety conditions that occur on a
Locked Out compressor cause the other compressor to
shutdown or prevent it from starting.
"Motor Controller [#1/#2] – Contacts Open"
"Oil Pump [#1/#2] – Drive Contacts Open"
"Proximity Probe – Low Supply Voltage"
"Discharge [#1/#2] – Low Temperature"
"Discharge [#1/#2] – High Temperature"
JOHNSON CONTROLS
SECTION 1 – DESCRIPTION OF SYSTEM AND FUNDAMENTALS OF OPERATION
"Oil Pump [#1/#2] - Differential Pressure Calibration"
"Oil Pump [#1/#2] – Pressure Transducer Out of
Range"
"Thrust Bearing [#1/#2] – Proximity Probe Clearance"
"Thrust Bearing [#1/#2] - Proximity Probe Out of
Range"
When any of these conditions occur on a locked out
compressor, they are displayed as Warnings. This al-
lows the user to know that a condition exists on the
locked compressor. The condition must be corrected
prior to the lock-out being removed from the compres-
sor. If it is not, the warning condition will revert back
to a safety as soon as the lockout is removed and will
cause the chiller to trip.
Normal Or Single Compressor Mode
The COMPRESSOR MODE Setpoint, available on the
Capacity Compressor Cycling Screen, is used to se-
lect either NORMAL Mode or SINGLE COMPRES-
SOR Mode. In Normal Mode, the second compressor
is brought on line to meet the load requirement as de-
scribed previously. In Single Compressor Mode, op-
eration is restricted to one compressor. The Lag com-
pressor will not be brought on line, regardless of the
load requirement.
When starting the chiller in Single Compressor mode,
the operator does not designate which compressor will
run. Rather, the "Lead" compressor is automatically
selected by the software per the present software op-
eration. The software to select the "Lead" compressor
has not changed.
If Single Compressor Mode is selected while both
compressors are running, a soft shutdown is performed
on the "Lag" compressor. All faults for this inhibited
compressor are continued to be handled.
If the chiller is shutdown while running in Single Com-
pressor mode, the software selects the "Lead" com-
pressor as it normally does on a subsequent restart.

COMPRESSOR SHUTDOWN

There are two types of shutdowns performed on one
or both compressors; Soft Shutdowns and Fault shut-
downs.
During a Soft Shutdown, first the Pre-rotation Vanes
are driven closed. When the Vanes have fully closed
(or 210 seconds have elapsed, whichever occurs first),
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