(d) Control at start
Following control takes place when starting the condensing unit.
1. Turn ON the operation switch of Module controller.
2. As the low pressure (LP) picks up to the start condition (LP > Evaporation temperature setting value), the condensing unit starts 60
seconds later.
3. Opens the liquid injection solenoid valve synchronized with the start of compressor, and starts the discharge gas overheat degree
control.
4. At the compressor start, it raises the frequency to 40 Hz once. After operating for 105 seconds, it changes to the calculation frequency
control.
(e) Calculation frequency control
1. Suction gas pressure control
The cooling capacity by load is controlled with the low pressure (LP). The low pressure (LP) varies depending on the compressor speed
which changes depending on the operation frequency. In order to maintain a necessary cooling capacity, the low pressure (LP) value that
corresponds to the cooling capacity is set so as to control the inverter output frequency such that the low pressure (LP) being detected
by the low pressure sensor will become the set low pressure.
2. Operation stop by decreased low pressure (LP)
When the low pressure (LP) is lower than the preset stop pressure value (Low pressure cut value) (LP ≤ Low pressure cut value) and the
compressor frequency is 50 Hz or more, the hot gas bypass solenoid opens and, if it is lower than 50 Hz, the compressor stops after the
state of LP ≤ Low pressure cut value has continued for 2 minutes or more.
After that, if the low pressure (LP) picks up to the operation restart pressure value, it restarts automatically.
3. Setting of pressure setting value
Pressure setting value is set to the central value between the lower value of pressure setting (PsD) and the upper value of pressure
setting (PsU) . When Module controller code “r28” is set to 1, PsD is the value set in module controller code r01 and PsU is the value set in
module controller code r02. When Module controller code “r28” is set to 0, PsD is the value +1.0bar from value set with rotary SW of the
condensing unit and PsU is the value -1.0bar from value set with rotary SW of the condensing unit.
User Guide | Optyma™ iCO2
© Danfoss | Climate Solutions | 2023.01 | LCA012A030
BC408445719305en-000101 | 9
