157
FORM 160.54-M1
ISSUE DATE: 10/25/2019
JOHNSON CONTROLS
JCI COMPANY CONFIDENTIAL
15
SECTION 15 - PROXIMITY PROBE
The following applies to all applications except P com-
pressors and style F
(and later)
c
hillers with “G, Q” or
“H5-8” compressors. For chillers equipped with P com-
pressors, see
SECTION 16 - HIGH SPEED THRUST
The Proximity probe sens-
es the distance between the tip of the Proximity probe
and the surface of the High Speed Thrust Collar. An
earlier vintage Probe (025-30961-000) also sensed the
High Speed Drain Line Oil Temperature. However, re-
gardless of which Probe is installed, chillers equipped
with Flash memory card version C.MLM.01.03 or later
do not sense the High Speed Drain Line Oil Tempera-
ture. The different vintages of Proximity probes are
shown at the end of this section.
The output of the Proximity circuit is connected to the
microboard at J8-15 and is a 0 (0.089 VDC) to +4.4
VDC analog voltage corresponding to a measured dis-
tance of 10 to 99 mils. This is the PROXIMITY PO-
SITION and is displayed as HIGH SPEED THRUST
BEARING PROXIMITY POSITION = XX MILS on
the Proximity probe CALIBRATION Screen. The out-
put of the 025-30961-000 Probe Temperature Circuit is
connected to the microboard at J8-1 and is a 0 to +4.5
VDC analog voltage corresponding to a measured tem-
perature of 0°F (-177°C) to 300°F (148.9°C). This is the
OIL DRAIN LINE TEMPERATURE and is displayed
as HIGH SPEED THRUST BEARING OIL DRAIN
TEMPERATURE = XXX°F on the COMPRESSOR
Screen (not applicable to Flash memory card version
C.MLM.01.03 or later).
When the Probe is installed at the time of chiller manu-
facture, a reference position is established. It is the dis-
tance between the tip of the Probe and the surface of the
High Speed Thrust Collar with a minimum of 25 psid
oil pressure. Any distance between 37 and 79 mils is ac-
ceptable. It is established using a calibration procedure
in
SECTION 33 - SYSTEM CALIBRATION, SERVICE
SETPOINTS, AND RESET PROCEDURES
of this
manual. This value is entered at the keypad as the Refer-
ence Position setpoint using the Proximity probe CALI-
BRAITION Screen. Distances outside the range of 37 to
79 mils will be rejected. The value is logged on a label
adhered to the inside of the OptiView Control Center
door. This value remains the Reference Position until the
compressor is rebuilt, whereupon the calibration proce-
dure must be repeated to establish a new Reference Posi-
tion. Since this Reference Position value is stored in the
BRAM (U52) memory device on the microboard, field
replacement of either of these items requires the Refer-
ence Position setpoint to be programmed again.
The difference between the Reference Position and the
actual Position is the PROXIMITY DIFFERENTIAL
and is displayed as HIGH SPEED THRUST BEAR-
ING PROXIMITY DIFFERENTIAL = XX MILS on
the COMPRESSOR Screen. For example, if the Ref-
erence Position is 50 mils and the actual Position is
45 mils, then the Differential is -5 mils; with the same
Reference, if the actual Position is 55 mils, the Differ-
ential is +5 mils.
If the Differential increases to greater than or equal to
10 mils (+10, +11, etc.) or decreases to greater than or
equal to 25 mils (-25, -26, etc.), a safety shutdown is
performed and THRUST BEARING - Proximity probe
CLEARANCE is displayed. With software version
C.MLM.01.10.xxx (and later) or C.OPT.01.10.302
(and later), the clearance is only checked during the
last 20 seconds of “System Pre-lube”, during “System
run” and during “Coastdown”. Therefore, the fault
is only detected during those periods. With all previ-
ous software versions, the clearance is continually
checked. The –25 threshold must be exceeded for 2
continuous seconds to initiate a shutdown. The amount
of time the +10 threshold has to be exceeded is depen-
dent upon the software version. With software version
C.MLM.01.10.xxx (and later) or C.OPT.01.10.302
(and later), the +10 threshold must be exceeded for
2 continuous seconds to initiate a shutdown. With all
previous software, the +10 threshold only has to be ex-
ceeded for an instant to initiate a shutdown.
If the Reference Position is between 37 and 46 mils,
the full -25 mil differential is not allowed; the maxi-
mum allowed distance between the tip of the Probe and
the surface of the Thrust Collar is 23 mils. Therefore,
when the distance decreases to less than or equal to 22
mils, the safety shutdown is performed, regardless of
the Differential to the Reference Position.
If the distance decreases to less than or equal to -17
mils, a safety shutdown is performed and “THRUST
BEARING - Proximity probe OUT OF RANGE” is
displayed.