Carrier 30XW Installation, Operation And Maintenance Instructions page 33

13.7.2 - 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 and can even
destroy it.
The reverse rotation protection scheme must be capable of
determining the direction of rotation and stopping the
com-pressor within one second. Reverse rotation is most
likely to occur whenever the wiring at the compressor
terminals has been modified.
To minimise the opportunity for reverse rotation, the follow-
ing procedure must be applied. Rewire the power cables to
the compressor terminal pin as originally wired. Apply a
counter-torque at the lower nut at the supply cable terminal
during installation.
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.
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