INSTALLATION INSTRUCTIONS
R
−
410A Split System Air Conditioner
8
421 01 5104 02
Specifications subject to change without notice.
Disconnect factory provided wires from DX+, DX
−
, C and R
terminals. Using factory provided wires, connect to C and Y
on the control board for 2 wire thermostat control. A field
installed jumper wire is also required between R and Y (See
Fig. 12). Connect field 24V wires to factory provided wires
now connected to C and Y and cap both sides or remove
unused factory provided wires.
Compressor Internal Relief
The compressor is protected by an Internal Pressure Relief
(IPR) which relieves discharge gas into the compressor shell
when differential between suction and discharge pressure
exceeds 550
−
625 psi. The compressor is also protected by
an internal overload attached to motor windings.
GENERAL SEQUENCE OF OPERATION
STANDARD THERMOSTAT
Turn on power to indoor and outdoor units. Transformer is
energized.
On a call for cooling, thermostat makes circuits R
−
Y and
R
−
G. Circuit R
−
Y energizes contactor, starting outdoor fan
motor and compressor circuit. R
−
G energizes indoor unit
blower relay, starting indoor blower motor on high speed.
NOTE
: To achieve the rated system performance, the indoor
unit or the thermostat must be equipped with a time delay
relay circuit.
W h e n t h e rm o s t a t i s s a t i s f i e d , i t s c o n t a c t s o p e n ,
de
−
energizing contactor and blower relay. Compressor and
motors stop. If indoor unit is equipped with a time
−
delay relay
circuit, the indoor blower will run an additional 90 sec to
increase system efficiency.
CONTROL FUNCTIONS
AND SEQUENCE OF OPERATION
The outdoor unit control system has special functions. The
following is an overview of the control functions.
SEQUENCE OF OPERATION
Cooling Operation
This product utilizes either a standard indoor thermostat or
Observer
t
Communicating Wall Control. With a call for
cooling, the outdoor fan and compressor are energized.
When the cooling demand is satisfied, the compressor and
fan will shut off.
NOTE
: The outdoor fan motor will continue to operate for one
minute after compressor shuts off, when the outdoor ambient
is greater than or equal to 100
_
F (37.78
_
C).
Communication and Status Function Lights
Green Communications (COMM) Light (Communicating
Control only):
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
An amber colored STATUS light is used to display the
operation mode and fault codes as specified in the
troubleshooting section. See Table 3 for codes and
definitions.
NOTE
: Only one fault code will be displayed on the outdoor
unit control board (the most recent, with the highest priority).
Crankcase Heater Operation
The crankcase heater (when applicable) is energized during
the off cycle below 65
_
F (37.78
_
C)
Outdoor Fan motor Operation
The outdoor unit control energizes outdoor fan any time the
compressor is operating. The outdoor fan remains energized
for 15 minutes if a pressure switch or compressor thermal
protector 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
(37.78
_
C).
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 communicating wall
control.
S
When operating the unit with 2 wires, this delay is
shortened to 10 seconds.
S
Five minute compressor recycle delay on return from a
brown out condition
S
Two minute time delay to return to standby operation from
last valid communications (with communicating 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 (37.78
_
C).
Utility Interface
With Non
−
Communicating Thermostats
Utility curtailment will only work when the unit is operating
with a non
−
communicating thermostat.
When the utility curtailment interface is applied with a
non
−
communicating thermostat, the utility relay should be
wired in series with the Y input.
Low Ambient Cooling
When this unit is required to operate below 55
_
F (12.78
_
C) to
a minimum of 0
_
F (
−
17.78
_
C) outdoor temperature,
provisions must be made for low ambient operation.
Low ambient applications
require
the installation of
accessory kits:
S
Low Ambient Pressure Switch Kit
S
Evaporator Freeze Thermostat
S
Hard Start kit
S
Crankcase Heater
Support feet are recommended for low ambient cooling. See
Product Specification sheet for kit part numbers on
appropriate unit size and series unit.
F o r l o w a m b i e n t c o o l i n g w i t h t h e O b s e r v e r
Communicating Wall Control the cooling lockout must be
set to “Off” in the Wall Control setup.
Liquid Line Solenoid
When operating in communicating mode the standard
thermostat terminals will not function. A terminal on the
non
−
communicating thermostat bus labeled “LS” on the AC
control board is provided for wiring liquid line solenoids when
in communicating mode. For operation in communicating
mode wire solenoid valve kit NASA401LS across LS and C
