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INSTALLATION INSTRUCTIONS
5. Set room thermostat to COOL and fan control to ON or
AUTO mode, as desired. Operate unit for 15 minutes.
Check system refrigerant charge.
Check Charge
Two−stage equipment should be charged in high stage
compressor operation only.
Factory charge amount and desired subcooling are shown
on unit rating plate. Charging method is shown on information
plate inside unit. To properly check or adjust charge,
conditions must be favorable for subcooling charging.
Favorable conditions exist when the outdoor temperature is
between 70_F and 100_F (21.11_C and 37.78_C), and the
indoor temperature is between 70_F and 80_F (21.11_C and
26.67_C). Follow the procedure below:
Unit is factory charged for 15ft (4.57 m) of lineset. Adjust
charge by adding or removing 0.6 oz/ft of 3/8 liquid line
above or below 15ft (4.57 m) respectively.
For standard refrigerant line lengths (80 ft/24.38 m or less),
allow system to operate in cooling mode at least 15 minutes.
When operating with the Observer Wall Control in
communicating mode, make sure that indoor airflow is set to
the final operating selection (Eff 325, Eff 350, Comfort,
Maximum) during charging. If conditions are favorable, check
system charge by subcooling method. If any adjustment is
necessary, adjust charge slowly and allow system to operate
for 15 minutes to stabilize before declaring a properly
charged system.
If the indoor temperature is above 80_F (26.67_C), and the
outdoor temperature is in the favorable range, adjust system
charge by weight based on line length and allow the indoor
temperature to drop to 80_F (26.67_C) before attempting to
check system charge by subcooling method as described
above.
If the indoor temperature is below 70_F (21.11_C), or the
outdoor temperature is not in the favorable range, adjust
charge for line set length above or below 15ft (4.57 m) only.
Charge level should then be appropriate for the system to
achieve rated capacity. The charge level could then be
checked at another time when the both indoor and outdoor
temperatures are in a more favorable range.
NOTE: The Observer Wall Control has a staging timer, to
override the staging timer for charging in high−stage create
at least a 5 degree difference between room and set point
temperatures and hold the "Cool To" button for 10 seconds
on the thermostat home screen.
NOTE: If line length is beyond 80 ft (24.38 m) or greater than
20 ft (6.10 m) vertical separation, See Long Line Applications
Guideline for special charging requirements.
SYSTEM FUNCTIONS AND SEQUENCE OF
OPERATION
The *CA9 and *CA7 models utilize either an Observer
Communicating Wall Control or a 2-stage cooling thermostat.
With a call for first stage cooling, the outdoor fan and
low-stage compressor are energized. If low-stage cannot
satisfy cooling demand, high-stage is energized by the
second stage of the indoor thermostat. After second stage is
satisfied, the unit returns to low-stage operation until first
stage is satisfied or until second stage is required again.
When both first stage and second stage cooling are satisfied,
the compressor will shut off. When a 2-stage unit is operating
at low-stage, system vapor (suction) pressure will be higher
than a standard single-stage system or high-stage operation.
When the outdoor ambient is more than 100°F (37.8°C), the
outdoor fan will continue to run for one minute after
compressor shuts off, this reduces pressure differential for
easier starting in the next cycle.
8
R−410A Split System Air Conditioner
Communication and Status Function Lights
Green communications (COMM) Light (Only
with Observer Communicating Wall Control)
A green LED (COMM light) on the outdoor board indicates
successful communication with the other system products.
The green LED will remain OFF until communications is
established. Once a valid command is received, the green
LED will turn ON continuously. If no communication is
received within 2 minutes, the LED will be turned OFF until
the next valid communication.
Amber Status Light (STATUS)
An amber colored STATUS light is used to display the
operation mode and fault codes as specified in the
troubleshooting section.
definitions.
NOTE: Only one code will be displayed on the outdoor unit
control board (the most recent, with the highest priority).
Utility Interface with Non-Communicating
Thermostat
The utility curtailment relay should be wired in the Y2
thermostat lead. This allows a power utility device to interrupt
high stage compressor operation during peak load periods. If
the utility requires control of low stage compressor operation
a second utility curtailment relay should be wired in the Y1
lead.
NOTE: Utility curtailment is not available when operating in
communicating mode. To apply utility curtailment with the
Observer Wall Control you must use a daughter board kit to
convert the control signals to standard thermostat signals.
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%.
solenoid in the compressor controlled by a rectified 24 volt
AC signal in the external solenoid plug 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
75% cooling capacity at the indoor coil. The compressor will
always start unloaded and stay unloaded for five seconds even
when the thermostat is calling for high−stage capacity.
Crankcase Heater Operation
The crankcase heater is de-energized when the compressor
is running. The crankcase heater is energized when the
compressor is off and the ambient is less than 42_ F. When
the ambient temperature is between 65_ F and 42_ F the
crankcase heater is energized 30 minutes after the
compressor is turned off. When the ambient is above 65_ F
See Table 6 for codes and
A DC
421 01 1701 00
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