1.11. Relay outputs CMC, LOW, MED and HIGH, SSR#2
Reserved.
1.12. On-status output AUX
Output AUX operates the unit status relay SRB. The SRB relay contacts provide an “On-status” signal.
The output is active when one or more of the following conditions apply:
• The compressor is on.
• The indoor fan is on.
• The compressor and indoor fan are currently off but the thermostat is on, e.g. the unit is off
in deadband, or the compressor may be held off by an internal safety timer, or by a
protection function.
1.13. Input IN#1
Reserved, leave open circuit.
1.14. Input IN#2
Input for an overload switch signal. If no overload signal is used the terminals must be shorted.
1.15. Modbus RTU serial communication port 1
Terminals A1 and B1 provide a serial communications port for a building management system (BMS)
or other type of monitoring and/or controlling device. The communications protocol is Modbus RTU
and the signals follow the RS485 standard. On this port the UC8 always acts as a Modbus slave device.
The RS485 signal reference is terminal 0V, which is directly connected to unit earth.
1.16. Modbus RTU serial communication port 2
Terminals A2 and B2 provide a serial communications port for a room thermostat and for the
compressor driver in a unit with inverter compressor. The communications protocol is Modbus RTU
and the signals follow the RS485 standard. On this port the UC8 always acts as a Modbus master
device. Refer to chapter 4.
The RS485 signal reference is terminal 0V, which is directly connected to unit earth.
Terminals “0V” (-) and “12” (+) provide 12V DC power that can be used to power the room
thermostat.
1.17. Electronic expansion valves
The UC8 controls an electronic expansion valve via output EXV1. Output EXV2 is normally not used
but can be used to control a second EEV. The signals on output EXV2 are a duplicate of the signals on
output EXV1.
1.18. Inputs D1, D2 and D3
Reserved, leave open circuit (not connected). Terminal SC is internally directly connected to terminals
labelled ‘0V’ and the EARTH terminal.
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