J & E Hall has launched a new range of HallScrew compressors with built-in variable frequency drive (VFD) and a variable volume ratio (VVR). For medium to high-temperature cooling applications, the compressors are designed, for use with R134a, R513A or R1234ze.

The new HallScrew compressor with VFD inverter technology proves to be significantly more efficient than operating the compressor at a fixed speed with slide control and can save up to 23% in energy consumption.  

The VVR allows the volume ratio to be adapted by moving the loading valves. It adapts the point at which the refrigerant leaves the compressor which changes the pressures at discharge. By doing this the volume ratio of the compressor is optimised for any running condition. 

Two versions of the compressors are available, with and without an integral oil separator. Models with integrated oil separator are said to be suitable for factory-built chillers with direct expansion evaporators. For flooded or spray type evaporator, HSV models should be used with an external oil separator.