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12.8 - Compressor maintenance
12.8.1 - Oil separator
Check the correct operation of the heaters and check that
they are well attached to the oil separator ring.
12.8.2 - Integral oil filter change
As system cleanliness is critical to reliable system operation,
there is a filter in the oil line at the oil separator outlet. The
oil filter is specified to provide a high level of filtration (5 µm)
required for long bearing life.
The filter should be checked after the first 500 hours of
operation, and every subsequent 2000 hours. The filter should
be replaced at any time when the pressure differential
across the filter exceeds 2 bar.
The pressure drop across the filter can be determined by
measuring the pressure at the filter service port and the oil
pressure port. The difference in these two pressures will be
the pressure drop across the filter, check valve, and solenoid
valve. The pressure drop across the check valve and solenoid
valve is approximately 0.4 bar, which should be subtracted
from the two oil pressure measurements to give the oil
filter pressure drop.
12.8.3 - Compressor rotation control
Correct compressor rotation is one of the most critical appli-
cation considerations. Reverse rotation, even for a very
short duration, damages the compressor.
The reverse rotation protection scheme must be capable of
determining the direction of rotation and stopping the com-
pressor within 300 milliseconds. Reverse rotation is most
likely to occur whenever the wiring to the compressor
terminals is disturbed.
To minimize the opportunity for reverse rotation, the follow-
ing procedure must be applied. Rewire the power cables to
the compressor terminal pin as originally wired.
For replacement of the compressor, a low pressure switch
is included with the compressor. This low pressure switch
should be temporarily installed as a hard safety on the high
pressure part of the compressor. The purpose of this switch
is to protect the compressor against any wiring errors at
the compressor terminal pin. The electrical contact of the
switch would be wired in series with the high pressure switch.
The switch will remain in place until the compressor has
been started and direction of rotation has been verified; at
this point, the switch will be removed.
The switch that has been selected for detecting reverse
rotation is Carrier part number HK01CB001. This switch
opens the contacts when the pressure falls below 7 kPa. The
switch is a manual reset type that can be reset after the
pressure has once again risen above 70 kPa. It is critical
that the switch be a manual reset type to preclude the
compressor from short cycling in the reverse direction.
44
12.9 - Precaution for compresssor power supply bus
bar connection
This note applies to units using power supply bus bars with
riveted contact block at the level of the connection cages in
the control box. During re-connection it is imperative to:
•
engage each bus bar in the cage up to the stop
•
ensure visually that the bus bars have good contact at
the connection areas: there must not be any free move-
ment between the bus bar and the connection area
created by the fixing rivet of the contact block.
Connection of the contactor or current transformer
1
Power supply bus bar with riveted contact block
1
Contactor or current transformer connection zone
2
2
2
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