Page 2
FIGURE 1
SCROLL COMPRESSOR
DISCHARGE
SUCTION
I−APPLICATION
All major components (indoor blower/coils) must be
matched according to Lennox recommendations for the
compressor to be covered under warranty. Refer to the
Engineering Handbook for approved system matchups. A
misapplied system will cause erratic operation and can re-
sult in early compressor failure.
II−SCROLL COMPRESSOR
The scroll compressor design is simple, efficient and re-
quires few moving parts. A cutaway diagram of the scroll
compressor is shown in figure 1. The scrolls are located in
the top of the compressor can and the motor is located in
the bottom of the compressor can. The oil level is immedi-
ately below the motor.
The scroll is a simple compression concept centered
around the unique spiral shape of the scroll and its inher-
ent properties. Figure 2 shows the basic scroll form. Two
identical scrolls are mated together forming concentric
spiral shapes (figure 3). One scroll remains stationary,
while the other is allowed to "orbit" (figure 4). Note that the
orbiting scroll does not rotate or turn but merely orbits the
stationary scroll.
NOTE − The head of a scroll compressor may be hot since
it is in constant contact with discharge gas.
FIGURE 2
SCROLL FORM
FIGURE 3
STATIONARY SCROLL
ORBITING SCROLL
DISCHARGE
SUCTION
CROSS−SECTION OF SCROLLS
TIPS SEALED BY
DISCHARGE PRESSURE
DISCHARGE
PRESSURE
The counterclockwise orbiting scroll draws gas into the out-
er crescent shaped gas pocket created by the two scrolls
(figure 4 − 1). The centrifugal action of the orbiting scroll
seals off the flanks of the scrolls (figure 4 − 2). As the orbit-
ing motion continues, the gas is forced toward the center of
the scroll and the gas pocket becomes compressed (figure
4 − 3). When the compressed gas reaches the center, it is
discharged vertically into a chamber and discharge port in
the top of the compressor (figure 1). The discharge pres-
sure forcing down on the top scroll helps seal off the upper
and lower edges (tips) of the scrolls (figure 3). During a
single orbit, several pockets of gas are compressed simul-
taneously providing smooth continuous compression.
The scroll compressor is tolerant to the effects of liquid re-
turn. If liquid enters the scrolls, the orbiting scroll is al-
lowed to separate from the stationary scroll. Continued
slugging of liquid will cause damage to the scroll and re-
placement will be necessary. The liquid is worked toward
the center of the scroll and is discharged. If the compres-
sor is replaced, conventional Lennox cleanup practices
must be used.
