Condensing Unit & Heat Pump R410A Service Manual

78
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 unloading mechanism
that opens a bypass port in the rst compression pocket,
eecvely 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 eciency motor connues to run
while the scroll modulates between the two capacity steps.
FIGURE A
A scroll is an involute spiral which, when matched with a mang
scroll form as shown, generates a series of crescent shaped gas
pockets between the two members.
During compression, one scroll remains staonary (xed scroll)
while the other form (orbing scroll) is allowed to orbit (but not
rotate) around the rst form.
As this moon 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, resulng in a very smooth process. Both the
sucon process (outer poron of the scroll members) and the
discharge process (inner poron) are connuous.
Some design characteriscs of the Compliant Scroll compressor
are:
• Compliant Scroll compressors are more tolerant of
liquid refrigerant.
NOTE: Even though the compressor secon of a Scroll
compressor is more tolerant of liquid refrigerant, connued
oodback or ooded start condions may wash oil from the
bearing surfaces causing premature bearing failure.
• “Ultratech” Series scroll compressors use “POE” or polyo-
lester oil which is NOT compable with mineral oil based
lubricants like 3GS. “POE” oil must be used if addional oil is
required.
• Compliant scroll compressors perform “quiet” shutdowns
that allow the compressor to restart immediately without
the need for a me delay. This compressor will restart even
if the system has not equalized.
NOTE: Operang pressures and amp draws may dier from
standard reciprocang compressors. This informaon can be
found in the unit’s Technical Informaon Manual.
CAPACITY CONTROL - LEGACY MODELS