10
MAJOR COMPONENTS
2--Stage Control Board
The HP control board controls the following functions:
S
High and low stage compressor contactor operation
S
Outdoor fan motor operation
S
Reversing valve operation
S
Defrost operation
S
Low ambient cooling
S
Crankcase heater operation
S
Compressor external protection
S
Pressure switch monitoring
S
Time Delays
Field Connections
On non--communicating (non--Infinity) system, the two--stage
control receives 24vac low--voltage control system inputs through
the Y1, Y2, and O connections located at the bottom of the control
board (see Fig. 7.) On a non--communicating system, output W1 is
connected to the control board for auxiliary heat.
For a communicating system, use the AB Infinity connections.
Two Stage Compressor
The two stage compressor contains motor windings that provide
2--pole (3500 RPM) operation.
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.
Compressor Control Contactor
The contactor has a 24volt coil. The electronic control board
controls the operation of the contactor.
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
Winding resistance at 70
_
F +/--- 20
_
F
(21.11
_
C +/--- 11.11
_
C)
024
036
048
060
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 Infinity control is lost with the User
Interface, the control will flash the appropriate fault code. (See
Table 6.) Check the wiring to the User Interface and the 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 Information
MODEL
NUMBER
MODEL PLUG
NUMBER
PIN RESISTANCE
(K---ohms)
Pins 1---4
Pins 2---3
25HNB624
HK70EZ041
18
91
25HNB636
HK70EZ043
18
150
25HNB648
HK70EZ045
18
220
25HNB660
HK70EZ047
18
360
25HNB924
HK70EZ010
5.1
120
25HNB936
HK70EZ012
5.1
180
25HNB948
HK70EZ014
5.1
270
25HNB960
HK70EZ016
11
5.1
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. An RCD replacement board contains 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.
NOTE
:
The model plug takes priority over factory model
information input at the factory. If the model plug is removed after
initial power up, the unit will operate according to the last valid
model plug installed, and flash the appropriate fault code
temporarily.
Pressure Switch Protection
The outdoor unit is equipped with high-- and low--pressure
switches. If the control senses the opening of a high-- or
low--pressure switch, it will respond as follows:
1. De--energize the compressor contactor.
2. Keep the outdoor fan operating for 15 minutes.
3. Display the appropriate fault code (see Table 6).
4. After a 15 minute delay, if there is a call for cooling or heat-
ing and LPS or HPS is reset, the compressor contactor is
energized.
5. If LPS or HPS has not closed after a 15 minute delay, the
outdoor fan is turned off. If the open switch closes anytime
after the 15 minute delay, then resume operation with a call
for cooling or heating.
6. If LPS or HPS trips 3 consecutive cycles, the unit operation
is locked out for 4 hours.
7. In the event of a high--pressure switch trip or high--pressure
lockout, check the refrigerant charge, outdoor fan operation,
and outdoor coil (in cooling) for airflow restrictions, or in-
door airflow in heating.
8. In the event of a low--pressure switch trip or low--pressure
lockout, check the refrigerant charge and indoor airflow
(cooling) and outdoor fan operation and outdoor coil in
heating.
Control Fault
If the outdoor unit control board has failed, the control will flash
the appropriate fault code (see Table 6). The control board should
be replaced.
Brown--Out Protection
If the line voltage is less than 187v for at least 4 seconds, the
appropriate compressor contactor and fan relay are de--energized.
Compressor and fan operation are not allowed until voltage is a
minimum of 190v. The control will flash the appropriate fault code
(see Table 6).
230V Brown--Out Protection Defeated
The brownout feature can be defeated if needed for severe noisy
power conditions. This defeat should always be a last resort to
solving the problem. Defeat is available on the User Interface
setup screen (available with SYSTXBBUID01--C), or can be
initiated through the forced defrost pins for non--communicating
systems as follows:
The brownout toggle is accomplished by sorting the defrost pins
from power up with the OAT and OCT sensor connector removed.
After 3 seconds, the status of the force defrost short and the
OAT/OCT as open will be checked. If correct, then the brownout
will be toggled.
Status code 6 shows the brownout is disabled.
Status code 5 shows the brownout is active.
25H
N
B
6
/25H
N
B
9
