Rhoss chiller unit utilises ABB AC drive
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A chiller unit utilising a scroll compressor and ABB standard drive is set to generate 15 per cent lower energy consumption than models with a traditional compressor design.
The unit has been produced by air-conditioning manufacturer, Rhoss.
Scroll compressors pressurise the refrigerant between two interleaved spirals or scrolls, resulting in a design with fewer moving parts, less noise and reduced vibrations compared with other compressor types.
Variation of output is traditionally provided by mechanical means, for instance by splitting the cooling capacity of the chiller into several circuits.
However, by using the ABB standard drive, Rhoss has achieved better performance while using a simple design with a single circuit.
The chiller unit has been designed to provide the best energy performance across the seasons.
Chillers only need to run at full capacity for short periods during the summer, yet most equipment of this type is designed for operation at full load only, resulting in oversupply for most parts of the year.
Rhoss used the ABB standard drive to raise the unit’s efficiency at part load, improving the seasonally adjusted energy efficiency.
Scroll compressors are favoured in heating, ventilation and air-conditioning (HVAC) applications as they are compact, smooth running, quiet and reliable.
The ABB standard drive matches the compressor speed to the cooling load, reducing input power.
In addition, the reduced speed results in lower flow through the condensers, giving the same effect as if the condensers were oversized, and further improves the efficiency.
This leads to up to 15 per cent lower energy consumption overall, compared with standard scroll-compressor systems with on/off control.
Variable speed control of the compressor also enables more accurate control of the discharge water temperature, to +/- 0.5C.
Stepless capacity control of the compressor gives a wide operating range and reduces the number of on/off switching cycles, limiting compressor wear.
The unit draws low starting current, as the ABB standard drive also acts as a soft-starting device.
The new chiller unit has a nominal cooling capacity of 48kW.
It uses a scroll compressor especially designed for variable-speed operation, an 18.5kW ABB standard drive and a motor dimensioned to work above 50Hz.
The output frequency of the drive varies between 35Hz and 90Hz.
The compressor uses R407, a modern refrigerant with low global-warming potential.
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