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Scroll compressors, VCH115 | Application
CC-000201
2
4m (13ft)*
5
3
4m (13ft)*
2
5
Oil separator
Oil separator is manditory, it removes oil from the compressor's discharge gas, and return it to the
compressor's crankcase. Oil separators are located close to the compressor in the discharge line.
Floating valve oil separators are the easiest to implement in the system. Oil return connection must be done on the
suction line after suction pressure and temperature sensors have been used for superheat control.
The outlet of the oil separator must be equipped with a non-return valve in order to prevent liquid refrigerant from
migrating back from the condenser.
To avoid having the oil separator act as a condenser, do not place it in the air ow or oversize it. If air ow is
unavoidable, the oil separator must be insulated.
Some separators require an initial oil charge to oat the needle valve oat.
For installation and dimensioning, always follow manufacturer recommendations
Figure 18: Oil separator
4
3
2
1
Manage Superheat
During normal operation, refrigerant enters the compressor as a superheated vapor. Liquid ood back occurs
when some refrigerant returns to the compressor in a liquid state. Liquid ood back can cause oil dilution and, in
extreme situations, lead to liquid slugging that can damage the compressor.
In steady state conditions, suction superheat must be maintained within 5K to 30K (9 to 54°F) and oil superheat
must be higher than 12K (21.6°F). In transient conditions, oil superheat below 12K (21.6°F) must not last more than
60s per event. Note: oil superheat criterion is mainly used during quali cation to con rm liquid ood back is
acceptable. It is not mandatory to monitor it on production unit.
© Danfoss | Climate Solutions | 2023.08
4
HP
LP
1
CC-000105
5
6
1
Evaporator
2
0.5% slope, 4m/s or more (13ft/s or more)
3
8 to 12m/s (26 to 40ft/s)
4
To condenser
5
U-trap, as short as possible
*
max.
1
Compressor
2
Oil separator
3
Oil return
4
Non return valve
5
Pressure sensor
6
Temperature sensor
AB392939083370en-000202 | 39
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