GSZH5 Service Manual
57
PRODUCT DESIGN
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
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%
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.
scroll) while the other form (orbiting scroll) is allowed to
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
compressor are:
• Compliant Scroll compressors are more tolerant of
liquid refrigerant.
compressor is more tolerant of liquid refrigerant,
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 lubricants 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.
This information can be found in the unit’s Technical
Information Manual.
Capacity Control - Legacy Models
During the compression process, there are several pockets
within the scroll that are compressing gas. Modulation is
pocket back to the low side of the compressor thereby
See Figure A. Full capacity is achieved by blocking these
vents, increasing the displacement to 100%. A solenoid in
the compressor, controlled by an external 24-volt ac signal,
moves the slider ring that covers and uncovers these vents.
The vent covers are arranged in such a manner that the
compressor operates somewhere around 67% capacity
when the solenoid is not energized and 100% capacity
when the solenoid is energized. The loading and unloading
unloaded mode default was chosen for two reasons: