CC-000201
HP
2
4
2
5
5
1
LP
3
4m (13ft)*
4m (13ft)*
1
2
3
4
5
*
Evaporator
0.5% slope, 4m/s or more (13ft/s or more)
8 to 12m/s (26 to 40ft/s)
To condenser
U-trap, as short as possible
max.
6
2
1
3
4
5
CC-000105
1
2
3
4
5
6
Compressor
Oil separator
Oil return
Non return valve
Pressure sensor
Temperature sensor
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
airflow
or oversize it. If
airflow
is
unavoidable, the oil separator must be insulated.
Some separators require an initial oil charge to
float
the needle valve
float.
For installation and dimensioning, always follow manufacturer recommendations
Figure 18: Oil separator
Manage Superheat
During normal operation, refrigerant enters the compressor as a superheated vapor. Liquid
flood
back occurs
when some refrigerant returns to the compressor in a liquid state. Liquid
flood
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
qualification
to
confirm
liquid
flood
back is
acceptable. It is not mandatory to monitor it on production unit.
© Danfoss | Climate Solutions | 2023.08
AB392939083370en-000202 | 39
Scroll compressors, VCH115 | Application