Danfoss AK-CC55 Water Loop User Manual page 15

AK-CC55 Water Loop
in the system and will not return to the compressor. The oil return management feature will prevent this from
happening. If the variable speed compressor has been running below a set oil return speed for a set period of time,
the compressor will increase the speed for a defined period of time and thereby ensure that oil is returned to the
compressor due to the higher refrigerant velocity in the pipes.
Figure 20: Oil return speed
Y
A
B
C
Resonance elimination
Speed control can cause mechanical resonance vibrations to occur in the system and thereby create irritating noise.
To prevent this, AK-CC55 Water Loop features an option of eliminating the speed range where the mechanical
vibrations are present.
The speed resonance range is defined as a minimum resonance limit and a resonance zone. Within the defined
resonance range, the speed will be kept constant - please refer to the curve below.
Figure 21: Resonance curve
Y
Compressor safety monitoring
The safety chain of the compressor or alternatively a speed drive can be monitored via a digital input signal. If the
safety chain is broken e.g. HP switch open, a compressor safety alarm will be generated, and the compressor will be
stopped. Once the problem has been remedied, the compressor will be started, provided that the min. OFF timer for
the compressor has expired.
For the dual compressor application, only an alarm will be generated as it is not possible to identify which
compressor that has been cut-out on safety.
© Danfoss | Climate Solutions | 2022.04
X
D
A
B
X Time
Y Compressor speed %
A P79 Oil return speed
B P77 Oil return speed limit
C P78 Oil return interval runs out
D P80 Oil return time period
X Requested capacity
Y AO1 voltage
A P40 Resonance band
B P39 Resonance band start
X
BC378540472015en-000101 | 15