163
FORM 160.54-M1
ISSUE DATE: 10/25/2019
JOHNSON CONTROLS JCI COMPANY CONFIDENTIAL
16
SECTION 16 - HIGH SPEED THRUST BEARING LIMIT SWITCH
Chillers that are equipped with P compressors and style
"F" and later chillers with G or “H5-8” compressors
have a High Speed Thrust Bearing Limit Switch (025-
34535-000) instead of the Proximity probe described
in SECTION 15 - PROXIMITY PROBE. This device
detects abnormal bearing position through probe con-
tact instead of distance measurement as performed
with the Proximity probe.
The High Speed Thrust Bearing Limit Switch is an
assembly consisting of a pressure switch attached to
a probe that protrudes into the compressor housing.
When the bearing position decreases to greater than
the allowed position, it comes into contact with the
probe, causing the break-away probe to detach, expos-
ing the pressure switch to the pressure inside the com-
pressor. A set of normally closed contacts inside the
switch open when the switch is exposed to a pressure
of greater than 15 to 25 psig. One side of these contacts
is connected to 115 VAC. The other side connects to
I/O Board TB3-81. The microboard reads the state of
these contacts through the I/O Board and when they
open, a safety shutdown is performed and THRUST
BEARING – LIMIT SWITCH OPEN is displayed on
the System Details line of the Display. On the COM-
PRESSOR Screen, a red LED illuminates when the
switch is closed; extinguishes when it is open.
After the HIGH SPEED THRUST BEAR-
ING safety shutdown has occurred, the
chiller cannot be restarted until a Thrust
Bearing inspection, followed by a special
reset procedure which has been performed
by a qualied Service technician. The
reset procedure and Bearing inspection
criteria are listed on page 271 of this
manual.
1
TB6
115VAC
I/O
BOARD
CONTROL CENTER
COMPRESSOR
TB3
81 1
2
FIGURE 70 - HIGH SPEED THRUST BEARING LIMIT SWITCH – INTERFACE
LD06866
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