Systems with reverse cycling and hot gas defrosting
Here, individual measures are necessary to protect the compressor from strong liquid slugging, increased oil carry over (e.g. due to rapid pressure reduction in the oil separator) and lack of oil. To do this, it must be ensured that the oil temperature when switching – depending on the refrigerant – is at least 20 to 30 K above the condensing temperature. In addition, the entire system must be carefully tested. A suction accumulator on the suction side is recommended to protect against liquid slugging. In addition, a pressure regulator immediately downstream of the oil separator (downstream of the compressor in the case of CS.) is recommended to limit the pressure drop.
The compressor should be stopped shortly before the changeover and restarted after pressure equalisation. Observe start and stop sequences, pause times and, if necessary, start unloading in accordance with the operating instructions. It must be ensured that no liquid is sucked into the compressor after switching and that it is operated again within the application limits as quickly as possible (see BITZER SOFTWARE).