Service Manual

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 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.