INSTALLATION INSTRUCTIONS
R-410A, Two-Stage Split System Air Conditioner
10
421 01 6001 00
SEQUENCE OF OPERATION
With power supplied to indoor and outdoor units,
transformer is energized.
NOTE
: For low-stage operation, the outdoor unit Comfort
Alert
UltraTech
is labeled Y and the indoor
unit/thermostat is labeled Y1.
On a call for low-stage cooling, the thermostat energizes Y1
(low-stage compressor) and G. The call for Y1 energizes
the contactor, starting the outdoor fan motor and low-stage
compressor. The compressor operates at part load. The
call for G energizes the indoor blower motor.
On a call for high-stage cooling, the thermostat energizes
Y1, Y2 and G. The call for Y1 energizes the contactor,
starting the outdoor fan motor and compressor. Five
seconds after the compressor starts, Y2 energizes the
compressor solenoid to load up the compressor to full
capacity. The call for G energizes the indoor blower
motor.
When the thermostat is satisfied, its contacts open,
de-energizing contactor and blower. Compressor and
motor stop.
NOTE:
If indoor unit is equipped with a time-delay relay
circuit, the blower runs an additional length of time to
increase system efficiency.
COMPRESSOR OPERATION
The basic scroll design has been modified with the
addition of an internal unloading mechanism that opens
a by-pass port in the first compression pocket, effectively
reducing the displacement of the scroll. The opening and
closing of the by-pass port is controlled by an internal
electrically operated solenoid. The modulated scroll uses
a single step of unloading to go from full capacity to
approximately 67% capacity.
A single speed, high efficiency motor continues to run
while the scroll modulates between the two capacity
steps. 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.
Full capacity is achieved by blocking these vents, thus
increasing the displacement to 100%. A DC solenoid in
the compressor, controlled by a rectified 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 at approximately 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.
NOTE:
67% compressor capacity translates to
approximately 80% cooling or heating capacity at the
indoor coil.
The compressor will always start unloaded and stay
unloaded for five seconds even when the second stage
of the thermostat is calling for more capacity (a starting
advantage under low voltage conditions).
