York YK Style H Operation Manual page 188

Motor Or Starter – Current Imbalance
The three phase compressor motor current imbalance was greater than 30% continuously for 45
seconds. The imbalance is not checked until the chiller has been running for at least 45 seconds
and the average of the three phases of motor current is greater than 80% of the programmed 100%
chiller Full Load Amps. The average is calculated as:
The imbalance is calculated as:
The Style B Solid State Starter and Variable Speed Drive detects the unbalance condition and advise
the OptiView Control Center Microboard via serial communications. This safety shutdown is not
performed on Electromechanical Starter applications.
Thrust Bearing – Proximity Probe Clearance
(Chillers with J or H3 compressors)
The clearance between the compressor high speed thrust collar and the tip of the Proximity Probe
has increased more than +10 mils or decreased to less than -25 mils (for 2 continuous seconds)
from the Reference Position. The minimum allowed clearance is 23 mils. Therefore, if the Reference
position is less than 47 mils, the shutdown will occur when the actual clearance is less than 22 mils.
The clearance is only checked during the last 20 seconds of System Prelube, during System Run
and during coastdown. Therefore, the fault is only detected during those periods. Also, the +10 mil
threshold must be exceeded for 2 continuous seconds.
This shutdown must be evaluated by a qualified Service Technician prior to starting the chiller. Starting
the chiller without this evaluation could result in severe compressor damage. To prevent the chiller
from starting without the proper evaluation, restart is inhibited until the clearance is within acceptable
limits and a special reset procedure is performed by the Service Technician. The evaluation and reset
procedure are contained in OptiView Control Center - Service Instructions (Form 160.76-M1).
Thrust Bearing – Proximity Probe Out Of Range
(Chillers with J or H3 compressors)
The clearance between the compressor high speed thrust collar and the tip of the Proximity Probe
has decreased to less than 17 mils.
The clearance is only checked during the last 20 seconds of System Prelube, during System Run and
during coastdown. Therefore, the fault is only detected during those periods.
188
CAUTION
Model YK Style H Centrifugal Liquid Chillers with OptiView Control Center