Daikin DAR09 - Page 44

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PRODUCT DESIGN
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 simultane-
ously being reduced in volume. When the pocket reaches the
center of the scroll form, the gas, which is now at a high pres-
sure, 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
During the compression process, there are several pockets with-
in the scroll that are compressing gas. Modulaon is achieved
by venng a poron of the gas in the rst sucon pocket back to
the low side of the compressor thereby reducing the eecve
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 uncov-
ers 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 y” without shung o the motor
between steps. See Figure B below. The unloaded mode default
was chosen for two reasons:
FIGURE B
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 heat-
ing if desired.
Unloader solenoid
A nominal 24-volt direct current coil acvates 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 connecon is made with a molded plug assembly. This
plug is connected to the Comfort Alert™ or CoreSense™ Module
(dependent upon which module you are using) which contains a
full wave recer to supply direct current to the unloader coil.