Specifications

RK0YG302 © Danfoss 04/2007 21
AK-PC 730
Example
The example below uses 2 no. AK-PC 730 to control a complete
cascade system with R404A for refrigeration and e.g. CO
2
for freezing.
High-pressure circuit
Consists of 3 compressors, of which the rst is speed-controlled
via a frequency converter type AKD.
The condenser consists of 4 fans which are all speed-controlled via
a frequency converter type AKD.
The compressor capacity is adjusted according to the pressure
measurement Pctrl which is located in the low-pressure circuit.
The suction pressure P0 is used for low-pressure monitoring.
Low-pressure circuit
Consists of 2 compressors, of which one is speed-controlled via a
frequency converter type AKD. Here the pressure measurement
Pctrl is used as high-pressure monitoring.
Coordination
Start-up coordination between high-pressure and low-pressure
circuits can be carried out in two ways:
1) The low-pressure circuit is only allowed to start compressors
when at least one high-pressure compressor is running.
2) The high-pressure circuit starts compressors, when the load on
the low-pressure circuit requires that compressors should be
started.
Cascade heat exchanger
The injection in the cascade heat exchanger takes place via a step
motor valve type ETS and control type EKC 316. The signal for
start/stop of injection comes from AK-PC 730 in the high-pressure
circuit, but it could also come from the other AK-PC 730 in the
low-pressure circuit.