Manual code 75803707A.0708
Page 23 of 64
4.7.5 VERY LOW EXTERNAL TEMPERATURE KIT
CEA air-cooled condensers, combined with Tecnair LV direct expansion air conditioners, are equipped as
standard with air condensation pressure control via reduction of the air flow rate in accordance with the reduction in the
condensation pressure. This system is very effective at external temperatures down to about - 20°C, thanks also to a 180
second delay on intevention of the low pressure switch on compressor startup. At external temperatures below this level
and above all in the case of lengthy periods of non-use of the refrigeration circuit, the temperature of the liquid refrigerant
can become so low that, in spite of the above-mentioned delay, the low pressure switch trips on compressor startup, thus
making starting impossible.
This problem can be avoided by installing the “very low temperature kit” accessory, which consists of a
condenser flooding valve installed on the refrigerant connections of the air condenser.
When the condensation temperature falls below -20°C, the valve progressively closes the condenser outlet,
thereby flooding it and reducing proportionally the heat exchange. The refrigerant that bypasses the condenser is
gaseous and at high temperature; it mixes with the liquid refrigerant at very low temperature at the condenser outlet, so
that the resulting temperature is high enough to permit successful system startup. The volume of refrigerant present in
the circuit must therefore be sufficient to be able to almost completely flood the condenser coil. During summer
operation, however, the condenser coil must be almost completely free of liquid refrigerant in order to perform correctly.
An oversize receiver is therefore installed in order to accommodate in summer the extra quantity of refrigerant that is
required in winter to flood the condenser.
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