PHASE ROTATION
Scroll compressors designed to operate only in one direction. If opposite direction is required, swamp any two
phases at the main terminal block. Reciprocating compressors are able to run in either direction without any loss of
performance or reliability.
Special Note for units fitted with Scroll Compressors
Phase sequencing: the Scroll compressor is designed to operate with motor running in only direction. Mis-wiring of
phase power (phase reversal) will cause the compressor to operate in the wrong direction. The Scroll compressor
will run without damaging itself if phasing is improper, but it will not pump refrigerant and will draw minimal current.
In such a case, the internal winding line break will ultimately shut off the compressor. Depending upon the conditions
it could take up to 30 minutes to trip the internal winding protection. The compressor will be noisy, vibrate excessively
and the oil sump will become warm to hot when running backwards.
Because of the scroll compressor design and its capability to accommodate liquid slugging, both oil and refrigerant,
without causing compressor damage, there are some characteristic sounds that differentiate if from those normally
associated with reciprocating type compressors.
These sounds described below, are characteristics and do not affect reliability or indicate that the compressor is
defective.
Cautions
1. Three phase scrolls will only pump when running in right direction.
2. Verify rotation on initial start up by checking pressure.
3. To correct improper motor rotation, switch any two supply lines.
At Start-up:
Under conditions of low refrigerant flows (low suction pressures) such as start-up, a rating sound may emanate from
the compressor.
This is more like to be heard under conditions such as low ambient starts where it takes time to build sufficient head
pressure to allow the thermal expansion valve to flow sufficient refrigerant to increase the suction pressure. This
sound should diminish and disappear as the suction pressure increases.
At Shutdown:
The gas within the scroll expands and causes momentary reverse rotation until the discharge check valve seats.
This results in a flutter type noise.
Refrigerant Flooding:
If the compressor experience severe liquid slugging during the operation the compressor will make a loud rattling
sound.
This is normal because of the separation of the scrolls that allow the liquid refrigerant to pass through the compressor
without damaging it.
