Installation guide
INST ALLATION INSTRUCTIONS R- 410A Split System Air Conditioner
421 01 1702 05 7
Specifications subject to change without notice.
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.
See Table 6 for codes and 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 c ompression 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 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 the crankcase heater remains
de-energized after the compressor is turned off.
Outdoor Fan Motor Operation
The outdoor unit control energizes the outdoor fan any time the
compressor is operating. The outdoor fan remains energized if a
pressure switch or compressor overload should open. Outdoor
fan motor will continue to operate for one minute after the
compressor shuts off when the outdoor ambient is greater than or
equal to 100_F (37.8_C) to allow for easier starting during next
cooling cycle.
The outdoor fan motor is a PSC type. A fan relay on the control
board turns the fan off and on by opening and closing a high
voltage circuit to the motor. It does not change speeds between
low and high stage operation.
Time Delays
The unit time delays include:
S Five minute time delay to start cooling operation when
there is a call from the thermostat or user interface. To
bypass this feature hold the “Cool To” or “Heat To” button
on the Observer Wall Control for 10 seconds.
S Five minute compressor re- cycle delay on return from a
brown- out condition.
S Two minute time delay to return to standby operation from
last valid communication (Observer Communicating Wall
Control only).
S One minute time delay of outdoor fan at termination of
cooling mode when outdoor ambient is greater than or
equal to 100_F (37.8_C).
S There is no delay between staging from low to high and
from high to low capacity. The compressor will change from
low to high and from high to low capacity “on the fly” to meet
the demand.
TROUBLESHOOTING
If the compressor fails to operate with a cooling call, Table 4 can
be used to verify if there is any damage to the compressor
windings causing system malfunction.
Table 4 - Winding Resistance
Winding Resistance At 70F+/- 20F
(21.11C+/- 11.11C)
Winding 24 36 48 60
Start
(S- C)
1.64 1.52 1.86 1.63
Run
(R- C)
1.30 0.88 0.52 0.39
Systems Communication Failure
If communication with the Observer Communicating Wall Control
will flash the appropriate fault code. (See Table 6) Check the
wiring to the wall control, indoor and outdoor units.
Model Plug
Each control board contains a model plug. The correct model
plug must be installed for or the system to operate properly (see
Table 5).
Table 5 - Model Plug
Model
Number
Model Plug
Number
Pin Resistance
(kOhms)
Pin 1- 4 Pin 2- 3
*CA724 HK70EZ040 18 75
*CA736 HK70EZ042 18 120
*CA748 HK70EZ044 18 180
*CA760 HK70EZ046 18 270
The model plug is used to identify the type and size of unit to the
control.
On new units, the model and serial numbers are input into the
board’s memory at the factory. If a model plug is lost or missing at
initial installation, the unit will operate according to the information
input at the factory and the appropriate error code will flash
temporarily.
A FAST® Parts replacement board c ontains no model and serial
information. If the factory control board fails, the model plug must
be transferred from the original board to the replacement board
for the unit to operate.