Page 4
B − Compressor
The scroll compressor design is simple, efficient and requires
few moving parts. A cutaway diagram of the scroll compressor
is shown in figure 3. The scrolls are located in the top of the
compressor can and the motor is located just below. The oil lev-
el is immediately below the motor.
FIGURE 3
SCROLL COMPRESSOR
DISCHARGE
SUCTION
The scroll is a simple compression concept centered around
the unique spiral shape of the scroll and its inherent properties.
Figure 4 shows the basic scroll form. Two identical scrolls are
mated together forming concentric spiral shapes (figure 5). One
scroll remains stationary, while the other is allowed to "orbit" (fig-
ure 6). Note that the orbiting scroll does not rotate or turn but
merely orbits the stationary scroll.
The counterclockwise orbiting scroll draws gas into the outer
crescent shaped gas pocket created by the two scrolls (figure 6
− 1). The centrifugal action of the orbiting scroll seals off the
flanks of the scrolls (figure 6 − 2). As the orbiting motion contin-
ues, the gas is forced toward the center of the scroll and the gas
pocket becomes compressed (figure 6 − 3). When the com-
pressed gas reaches the center, it is discharged vertically into a
chamber and discharge port in the top of the compressor (figure
5). The discharge pressure forcing down on the top scroll helps
seal off the upper and lower edges (tips) of the scrolls (figure 5).
During a single orbit, several pockets of gas are compressed
simultaneously providing smooth continuous compression.
The scroll compressor is tolerant to the effects of liquid return. If
liquid enters the scrolls, the orbiting scroll is allowed to separate
from the stationary scroll. The liquid is worked toward the center
of the scroll and is discharged. If the compressor is replaced,
conventional Lennox cleanup practices must be used.
Due to its efficiency, the scroll compressor is capable of draw-
ing a much deeper vacuum than reciprocating compressors.
Deep vacuum operation can cause internal fusite arcing
resulting in damaged internal parts and will result in com-
pressor failure. Never use a scroll compressor for eva-
cuating or pumping−down" the system. This type of dam-
age can be detected and will result in denial of warranty
claims.
The scroll compressor is quieter than a reciprocating com-
pressor, however, the two compressors have much different
sound characteristics. The sounds made by a scroll compres-
sor do not affect system reliability, performance, or indicate
damage.
NOTE − During operation, the head of a scroll compressor may
be hot since it is in constant contact with discharge gas.
FIGURE 4
SCROLL FORM
FIGURE 5
STATIONARY SCROLL
ORBITING SCROLL
DISCHARGE
SUCTION
CROSS−SECTION OF SCROLLS
TIPS SEALED BY
DISCHARGE PRESSURE
DISCHARGE
PRESSURE