Control logic
Safety control logic
requirements
Tripping conditions
Re-start conditions
Value
Time
Value
Time
HP switch
See Pressure settings table
from section “Manage
operating envelope”
Immediate, no delay.
No by- pass
Conditions back to normal.
Switch closed again
Manual reset
LP safety switch
Maximum 5 auto reset during
a period of 12 hours, then
manual reset.
Electronic module
(Motor protection, DGT)
Contact M1-M2 opened
Cycle rate limit
requirements
Oil management logic
recommendations
Danfoss requires a minimum compressor running
time of 2 minutes to ensure proper oil return and
sufficient motor cooling.
Additionally, compressor service life is based on a
maximum of 12 starts per hour.
Therefore, to guarantee these 2 requirements,
a three-minute (180- sec) time out is
recommended.
In some cases, oil management can be enhanced
by control logic:
If oil return test failed, a function can be
integrated in control to run all compressors
simultaneously during one minute every hour in
order to boost oil return. Time and delay can be
fine-tuned by oil return test N°1 §Manage oil in
the circuit. During oil boost, pay special attention
to superheat management to avoid liquid flood
back and foaming.
If after running long time in full load, oil
unbalance appears, then a function can be in
control to stop all compressors in manifold
during one minute every two hours in order to
balance oil between compressors. Time and delay
can be fine-tuned by Oil balancing test N°2 §
Manage oil in the circuit.
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FRCC.PC.012.A7.02
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