Circuits For Control Of Co2 Gas Pressure - Danfoss AK-PC 772A User Manual

Circuits for control of CO2 gas pressure

Application
The controller regulates the pressure in the gas cooler (condenser)
so that the system achieves the optimal COP.
The controller will always optimise to a subcritical state.
The pressure in the gas cooler is controlled by the valve CCMT
valve with stepper motor can be used.
Regulation must have inputs from both a pressure transmitter Pgc
and a temperature sensor Sgc. Both must be fitted in the outlet
immediately after the gas cooler. The valve is an CCMT valve,
which has been specially developed for the pressure conditions
that exist in a transcritical CO 2 system. The valve's degree of open-
ing can be restricted both at the closing point and in the entire
open point.
The settings OD Min. and OD max. are adjusted as % of the degree
of opening.
Maximum COP control
During normal operation without override, the controller will
maintain the optimum pressure in the transcritical area.
Warning
Remember that the controller controls the gas pressure. If the
regulation is stopped by the internal or external main switch, this
control will stop as well.
Risk of loss of charge.
If the compressors are stopped via the function "External com-
pressor stop", control of the gas pressure will continue.
106
Important
This sensor must be placed
immediately at the gas
cooler outlet.
Capacity controller RS8HF102 © Danfoss 2017-07
Overview
Reference curve
The controller is pre-programmed to follow the optimal COP
from the pressure/enthalpy chart. The top point is defined at 100
bar, 39°C. (Optimal theoretical COP is achieved at the curve that
passes through 100 bar and 39°C. The point of intersection can be
changed by setting a value other than the default).
Regulation will now follow the set reference curve, but will never
go above the set permitted max. pressure for the gas cooler.
The current reference can be read from the controller's overview
screen.
Subcooling
It is also possible to configure the subcooling in the sub-critical
area..
AK-PC 772A