System design recommendations
Oil level regulator
Oil level regulator monitors the oil level and
controls oil injection by switching the solenoid
valve on and off to maintain an acceptable
oil level in the compressor crankcase. When
crankcase oil level cannot be restored within a
period of time (setting value), the alarm contactor
will be activated and stop the compressor to
protect it from damage (some oil level regulator
do not have an alarm function).
According to the function, there are three
types of oil level regulator: electronic,
electromechanical and mechanical. For a
high-pressure oil reservoir system, Danfoss
recommends individual electronic oil control
regulators rather than the mechanical float ball
oil regulator system for effective oil regulation.
To ensure ideal pressure equalization, the suction
header must be symmetrical and the lines from
the suction header to each compressor must be
short and identical. These recommendations are
not so critical when using an active system.
Danfoss recommends the following as necessary
for secure a suction header installation:
• The suction header should be adequately sized
for equal distribution of returning refrigerant gas
and oil to each individual compressor; also the
suction header should be installed horizontally.
• The gas velocity in the suction header must be a
maximum of 4 m/s.
• The suction line and the suction header must be
insulated to limit suction gas superheat.
Passive system
Oil separator / oil
reservoir
Oil separator for passive
system
The role of the oil separator is to intercept the
mixed oil from the compressed refrigerant gas
and returns it back to the compressor to assure
efficient lubrication of its moving parts, and
also to improve the system’s heat exchangers’
efficiency. In our manifolding system, the oil
separator is necessary and is recommend to be
installed in the compressor discharge line as
shown below.
No oil separator category is included in this
guidelines. For more details, please refer to the
manufacture’s guidelines.
Regarding passive solutions, it is recommended
to use an oil separator with a floating-ball
valve. The floating-ball valve can control the
oil flow and act as a capillary in the oil return
line; therefore, there is no need to install an oil
capillary in the system.
Compressor 1
Compressor 2
Suction header
From evaporator
To condenser
Oil equalization
line
Non-return valve
Non-return valve
Oil separator with
floating-ball valve
Oil filter
48
FRCC.PC.035.A4.02
Application Guidelines
Manifold compressors
