Goodman ASX Service Instructions Manual page 26

PRODUCT DESIGN
The ASX [16 & 18], ASZ [16 & 18], DSX16 and DSZ16 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%
capacity. 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.
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As this motion occurs, the pockets between the two forms
are slowly pushed to the center of the two scrolls while
simultaneously 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 com-
pressor are:
• Compliant Scroll compressors are more tolerant of liquid
refrigerant.
NOTE: Even though the compressor section of a Scroll
compressor is more tolerant of liquid refrigerant, contin-
ued floodback or flooded start conditions may wash oil
from the bearing surfaces causing premature bearing
failure.
• Compliant Scroll compressors use white oil which is
compatible with 3GS. 3GS oil may 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 informa-
tion can be found in the unit's Technical Information
Manual.