Eubank EAA/EGA Wall Mount AC Installation & Operation Manual
03/2021 Rev.5
29
5.0 – Refrigeration Protection
5.1– High Pressure Lockout
This condition describes the abnormal rise in Head Pressure pass the system acceptable limit of 660
PSI (+/-20PSI). The fault will only be active when the High-Pressure Switch (Normally Closed)
opens during a request for Cooling. The rst time this fault condition occurs, the system cuts the
compressor off WITHOUT locking out. Once the pressure normalizes (drops below 450 PSI), the
system will resume operation if the cooling call still exist. If this fault occurs a second time on the
same Cooling request, the system locks out. Lockouts can be monitored using the Status 1 and Status
2 LEDs. These LEDs correspond to a particular circuit and has a ash sequence associated to the
various faults. The faults can also be monitored via MODBUS by reading the respective value based
on the MODBUS map that is provided. After this lockout condition is reached, the cooling call must
be cycled (on/off of respective cooling request) or the system must be power cycled to clear the fault.
For a 2-compressor system, each lockout is isolated to the respective circuit and will not interfere
with the operation of the other circuit providing that the circuits operate independently. The system
will continue to lockout until the problem is rectied.
5.2– Low Pressure Lockout
This condition describes the abnormal fall in Suction Pressure below 40PSIG (+/- 5PSIG). This fault
will only be active when the Low-Pressure Switch (Normally Closed) opens up during a request for
Cooling. The Low-Pressure Switch is bypassed on the initial call for cooling for 3 minutes to allow
low ambient start-up of the system. Once these 3 minutes have elapsed, if the switch is still open,
the system cuts the compressor off. Once the pressure normalizes, the system will restart the cooling
operation. In the event that the fault occurs a second time on the same call for cooling, the system
locks out. To clear the fault, the Cooling request must be cycled or the system must be power cycled.
Status LEDs with associated ash codes or designated MODBUS values can be monitored to verify
this fault. The system will continue to lockout unit the problem is rectied.
5.3– Low Voltage
In the event that the board is experiencing low voltage (less than 20 Volts), both Status 1 and Status 2
LEDs ashes continuously (see LED Status Indicators). The board will not energize any outputs until
this problem is rectied. This fault can be monitored at the board level via LEDs or via MODBUS.
5.4– Anti-Short Cycle
This is a built-in protection mechanism that increases the reliability of the compressor by protecting
it from excessive short cycling. When the compressor goes off, due to any fault, emergency or if the
cooling setpoint is satised, a built-in 3-minute timer locks the compressor for that respective circuit
out. This can be monitored via MODBUS by referencing the appropriate register. However, it can
only be monitored at the board level by waiting for the 3 minutes to elapse.
6.0 – Additional Features
5.1 – MODBUS Communication
To control the board via MODBUS, the board ID must be non-zero. “Zero” a MODBUS ID represents
local control which allows the board to be controlled at the board level by Digital thermostatic inputs.
If the MODBUS ID is non-zero, the board ignores all inputs from the board and inputs used are based
on the MODBUS registers associated to the various Digital Inputs and Registers. Read Only registers
and Coils can still be monitored but all read/write values MUST be congured at the MODBUS
register/coil level and NOT at the board level.
The sequence of operation is the same as described above for the various operation, but Indoor
Motor speeds for various operation, Outdoor Motor Speed, Heating Setpoint and Cooling Setpoint (if
applicable) has to be congured via MODBUS. See MODBUS register tables at the end of this section.
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