Service Instructions

PRODUCT DESIGN
75
The ASX [16 & 18], ASZ [16 & 18], DSX[16 & 18] and DSZ [16 & 18]
series split system units use a two-stage scroll compressor. The
two-step modulator has an internal unloading mechanism that
opens a bypass port in the first compression pocket, effectively
reducing the displacement of the scroll. The opening and closing
of the bypass port is controlled by an internal electrically
operated solenoid.
The ZPS/ZRS two-step modulated scroll uses a single step of
unloading to go from full capacity to approximately 67% capac-
ity. A single speed, high efficiency motor continues to run while
the scroll modulates between the two capacity steps.
FIGURE A
A scroll is an involute spiral which, when matched with a mating
scroll form as shown, generates a series of crescent shaped gas
pockets between the two members.
During compression, one scroll remains stationary (fixed scroll)
while the other form (orbiting scroll) is allowed to orbit (but not
rotate) around the first form.
As this motion occurs, the pockets between the two forms are
slowly pushed to the center of the two scrolls while simulta-
neously being reduced in volume. When the pocket reaches the
center of the scroll form, the gas, which is now at a high pressure,
is discharged out of a port located at the center.
During compression, several pockets are being compressed
simultaneously, resulting in a very smooth process. Both the
suction process (outer portion of the scroll members) and the
discharge process (inner portion) are continuous.
Some design characteristics of the Compliant Scroll compressor
are:
Compliant Scroll compressors are more tolerant of liquid
refrigerant.
NOTE: Even though the compressor section of a Scroll com-
pressor is more tolerant of liquid refrigerant, continued
floodback or flooded start conditions may wash oil from the
bearing surfaces causing premature bearing failure.
"Ultratech" Series scroll compressors use "POE" or polyolester
oil which is NOT compatible with mineral oil based lubri-
cants like 3GS. "POE" oil must be used if additional oil is
required.
Compliant scroll compressors perform "quiet" shutdowns
that allow the compressor to restart immediately without the
need for a time delay. This compressor will restart even if the
system has not equalized.
NOTE: Operating pressures and amp draws may differ from
standard reciprocating compressors. This information can
be found in the unit's Technical Information Manual.