System design recommendations
Active system
Oil separator and
reservior for active
system
When an active system is adopted by the
customer, the oil separator is always considered
together with oil reservoir.
Due to system design, loads and defrost
cycles, etc., there will be varying amounts of oil
returning to the oil separator. Because of this,
a safety reserve of oil is required for successful
operation of the active system.
High pressure
Low pressure
Non-return
valve
Suction
header
Non-return
valve
Non-return
valve
Non-return
valve
Combined oil
separator/reservoir
Oil filter
Non-return
valve
Compressor 1
Oil level regulator
Oil level regulator
Oil level regulator
Oil level regulator
Compressor 2
Compressor 3
Compressor 4
Danfoss recommends that high-pressure
systems (oil separator installed in high pressure
side) are configured in active solutions. These
systems store the oil in a common oil separator/
reservoir at compressor discharge pressure (see
the figure below). The advantage is that these
systems do not need a separated oil reservoir but
make use of a combined oil separator/reservoir
arrangement ,which normally results in a cost
saving over traditional low-pressure systems
(additional oil separator and oil reservoir installed
in low pressure side). From an application point
of view, high-pressure systems are more critical
than traditional low pressure systems and care
must be taken to make sure that the separator/
reservoir installed is of sufficient size and oil
content (as per manufacturer’s recommendation)
so that there is always oil stored. And pay special
attention to avoid discharge gas entering the
compressor oil sump, which could lead to some
negative effects such as higher discharge and oil
temperatures, less lubrication capability and the
loss of efficiency due to hot gas bypass.
49
FRCC.PC.035.A4.02
Application Guidelines
Manifold compressors
