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PRODUCT DESIGN
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.
NOTE: Even though the compressor section of a Scroll
compressor is more tolerant of liquid refrigerant, continued
floodback or flooded start conditions may wash oil from the
bearing surfaces causing premature bearing failure.
•
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.
CAPACITY CONTROL - COMFORTNET™ MODELS
During the compression process, there are several pockets within
the scroll that are compressing gas. Modulation is achieved by
venting a portion of the gas in the first suction pocket back to
the low side of the compressor thereby reducing the effective
displacement of the compressor. 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 of the two
step scroll is done “on the fly” without shutting off the motor
between steps. See Figure C below. The unloaded mode default
was chosen for two reasons:
Molded Plug*
Line
Line
Run Capacitor
Internal Unloader
Coil
24 vdc
*Rectifier is integrated on the UC PCB
FIGURE C
1. It is expected that the majority of run hours will be in the
low capacity, unloaded mode.
2. It allows a simple two-stage thermostat to control capacity
through the second stage in both cooling and possibly
heating if desired.
UNLOADER SOLENOID
A nominal 24-volt direct current coil activates the internal
unloader solenoid. The input control circuit voltage must be 18
to 28 volt AC. The coil power requirement is 20 VA. The external
electrical connection is made with a molded plug assembly. This
plug is connected to the Communicating Unitary Control PCB (UC
PCB) which contains a full wave rectifier to supply direct current
to the unloader coil.
COILS AND BLOWER COILS
MBVC blower cabinets are designed to be used as a two-piece
blower and coil combination and can be utilized with the
CAUF, CAPF, CAPFA and CAPT coils for upflow and downflow
applications. The CACF and CHPF coils are designed for horizontal
applications. This two-piece arrangement allows for a variety of
mix-matching possibilities providing greater flexibility.
