Introduction; Application - Danfoss ADAP-KOOL AK-PC 783 Design Manual

Application

AK-PC 783 is complete regulating units for capacity control of
compressors and condensers in refrigeration plants with cascade
function.
The controller controls the high-pressure circuit, low-pressure
circuit and cascade circuit.
The controller is with oil management, simple heat recovery func-
tion and coordination between the high-pressure control and
low-pressure control.
In addition to capacity control the controllers can give signals to
other controllers about the operating condition, e.g. forced clos-
ing of expansion valves, alarm signals and alarm messages.
The controller's main function is to control compressors and
condensers so that operation all the time takes place at the
energy-optimum pressure conditions. Both suction pressure
and condensing pressure are controlled by signals from pressure
transmitters.
Capacity control is carried out by suction pressure P0 on the two
circuits.
Cascade control is performed in accordance with the two tem-
perature sensors, Scasc2 and Scasc3.
Among the different functions are:
- Capacity control of up to 8 compressors
(Max. 4 on each circuits or 5 on MT + 3 on LT)
- Up to 3 unloaders for each compressor
- Up to 3 screw compressors
- Digital scroll compressor
- Oil equalisation function on MT circuit
- Oil management. Either shared or individual for all of the com-
pressor's oil valves in the LT circuit. Receiver pressure control.
- Speed control of one or two compressors
- Up to 6 safety inputs for each compressor
- Option for capacity limitation to minimize consumption peaks
- When the compressor does not start, signals can be transmitted
to other controllers so that the electronic expansion valves will
be closed
- Control of liquid injection into suction line
- Control of liquid injection into screw compressor
- Control of liquid injection in heat exchanger (cascade)
- MT/LT - coordination between controllers in cascade control
- Safety monitoring of high pressure / low pressure / discharge
temperature
- Capacity control of up to 8 fans on the condenser
- Floating reference with regard to outside temperature
- Heat recovery function
- Step coupling, speed regulation or a combination
- Control of CO2 pump system
- Safety monitoring of fans
- Control of fans with EC motors
- The status of the outputs and inputs is shown by means of light-
emitting diodes on the front panel
- Alarm signals can be generated via data communication
- Alarms are shown with texts so that the cause of the alarm is
easy to see.
- Plus some completely separate functions that are totally inde-
pendent of the regulation – such as alarm, thermostat ,pressure
and PI-regulating functions.
AK-PC 783

1. Introduction

Capacity controller RS8GN202 © Danfoss 11-2013 3