Panasonic OCU-R200SF Service Manual page 37

Check Points and Settings for Operation
Superheat = suction temperature of compressor - evaporation temperature of refrigerant in evaporator.
With superheat, non refrigerant that enters into the compressor is in liquid state, which prevents the wet stroke.
In order to avoid wet stroke, a certain degree of suction superheat is required to ensure that only dry steam enters the compressor (the presence of
superheat indicates the complete evaporation of the liquid refrigerant due to the nature of the refrigerant). However, a higher superheat will increase the
discharge temperature（discharge superheat）of compressor, worsen compressor operating conditions and reduce the life. Therefore, the suction
superheat should be controlled within a certain range. Expansion valve senses temperature difference (suction superheat) between the back temperature
and the actual evaporation pressure(corresponding to the saturation temperature) through the temperature sensor placed at the compressor return-air duct
or the evaporator outlet. The opening of expansion valve is adjusted based on the set superheat, which is equivalent to adjusting the liquid supply of the
evaporator, and finally controlling the superheat of the suction superheat.
The recommended superheat of the unit should be controlled within 8~15K
Short cycle operation (frequent start/stop operation)causes excessive oil overfilling during starting and caused insufficient lubrication.
Adjust operation cycle to avoid short cycke operation. (ON-OFF cycle to be at least 10mins)
The main reason of short cycle operation is inappropriate setting of low pressure,suction filter clogging, and unbalance between cooling
capacity and load.
When a unit is used, incorrect fixed position of temperature sensor (cold air-blow should directly hit the sensor)would become a potential risk.
Check the operation condition of condensing unit
⑴ Checck if there is any vibration in the condensing unit or pipes.
⑵ Check if there is a shortage or overcharge of refrigerant (check the sight glass and high pressure)
⑶ Check the remaining water level (through sight glass, the green color is up to standard)
⑷ Check the oil amount in the compressor (through the sight glass of compressor or oil tank)
Note: sometimes it takes a few hours or days to stablize the oil level. So please monitor it and if the
oil is excessive or insuffient, adjust it accordingly.
⑸ Check if the rotation direction of condenser fan is the same with the direction of the arrow.
Suction Superheat of Compressor
Prevention of short cycle operation
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