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Pressure transmitters
• P0 Suction Pressure
Must always be used in connection with compressor regulation
(frost protection).
• Pc Condensing Pressure
Must always be used in connection with compressor or condenser
regulation
• Prec. Oil receiver pressure. Must be used for receiver pressure regulation.
• Paux (1-3)
Up to 3 extra pressure transmitters can be connected for monitoring and
data collection.
These sensors can be used for general pressure switch functions.
Note. A pressure transmitter type AKS 32 or AKS 32R can supply signals to
a maximum of five controllers.
Voltage signal
• Ext. Ref
Used if a reference override signal is received from another control.
• Voltage inputs (1-3)
Up to 3 extra voltage signals can be connected for monitoring and data
collection. These signals are used for general voltage input functions.
On/Off-inputs
Contact function (on an analog input) or
voltage signal (on an extension module)
• Common safety input for all compressors (e.g. common high-pressure/
low-pressure pressure switch)
• Up to 6 signals from the safety circuit of each compressor
• Signal from the condenser fans safety circuit
• Any signal from the frequency converter's safety circuit
• External start/stop of regulation
Example
Compressor group:
• MT circuits and LT circuits
• Refrigerant MT=134a LT=CO 2 (R744)
• 4 and 2 compressors with "cyclic" operation.
• Speed control of first compressor
• Safety monitoring of each compressor
• Common high-pressure monitoring in each circuit
• ToMT Setpoint =-10°C, ToLT = -30°C
• P0 optimisation
• Oil management of each LT compressor
• Pulse reset for stopped compressor (lack of oil)
Condenser:
• Fans with EC motors, speed controlled
• Pc-MT regulates flooating based on temperature sensor
Sc3
Cascade exchanger
• Control sensor =Scasc3
• Valves = Stepper valve ETS and Solenoid valve EVR
Receivers:
• Control of pressure in oil receiver
Safety functions:
• Monitoring of Po, Pc, Sd and superheat in suction line
• Monitoring of low and high level in oil receiver
Data from this example is used on the next page.
The result is that the following modules should be used:
• AK-PC 783 controller
• AK-XM 204A input and output module
• AK-XM 208C stepper output module
• AK-XM 102B digital input module
• AK-XM 103A analog input and output module
36
Capacity controller RS8GN202 © Danfoss 11-2013
• External day/night signal (raise/lower the suction pressure reference). The
function is not used if the "P0 optimization" function is used.
• DI alarm (1-10) inputs
Up to 10 no. extra on/off signals for general alarm for monitoring and
data collection can be connected.
• Level contacts
On/off-outputs
Relay outputs
• Compressors
• Unloaders
• Fan motor
• Injection On function (signal for evaporator controls. One per suction
group).
• Start/stop of liquid injection in heat exchanger
• Start/stop of liquid injection in suction line
• Start/stop of 3-way valves at heat recovery
• ON/OFF signal for start/stop of speed regulation
• Alarm relay. I'm alive relay.
• On/off signals from general thermostats (1-3), pressure switches (1-3) or
voltage input functions (1-3).
• Oil valves
• Safety relays for cutouts of compressors at oil failure
Solid state outputs
The solid state outputs on the controller module may be used for the
same functions as those mentioned under "relay outputs". (The output will
always be "OFF" when the controller has a power failure).
Analog output
• Speed regulation of the condenser's fans.
• Speed regulation of the compressor
• Stepper signal for expansion valve on cascade heat exchanger
AK-PC 783
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