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Autonomous pressure (evaporation temperature) control for cooling – Reg. P
In this mode, the outdoor unit compressor performance is controlled to keep the desired
pressure behind the indoor unit evaporator and thereby also the evaporating temperature of
the refrigerant R410A. The pressure is measured by the pressure sensor with the output of
4-20mA in the range of 0-18bar (relative). The resistance thermometer T1 measures the
temperature of the indoor unit evaporator and the SCMI-01.4 control module uses this
temperature to control the evaporator defrosting. The thermometer T2 measures the
temperature in the room. Placing of temperature sensor T2 depends on
installation‘s demands
.
The control module can be activated remotely using the digital input On/Off. If the input
On/Off is not connected, the module is switched off; if this input is connected to the
common terminal, the module is switched on. The outdoor unit is controlled via a serial
line, which also supplies its communication circuits. For 1-phase outdoor units, the terminals
SC-1 and SC-2 of the module must be connected to the terminals 1 and 2 of the outdoor unit,
respectively. For 3-phase outdoor units, the terminals are interchanged, so to work properly,
the terminals SC-1 and SC-2 of the module must be connected to the terminals 2 and 1 of
the outdoor unit, respectively.
Fig. 3. SCMI-01.4 control module in the autonomous pressure control mode
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