A key advantage of the modern screw compressor is its ability to have a variable load control across a wide band of operation, as opposed to piston compressors, which are limited to distinct step stages. Also, because pistons are still operating, even when unloaded, they waste a significant amount of the motor energy when partially loaded, even beyond that lost by the reciprocating motion.
With a stable discharge the primary refrigerant flow control device – Thermostatic Expansion Valve or Electronic Expansion Valve, can hold the refrigerant flow to a critical level whereby the superheat back at the compressor is closely controlled. This optimises compressor efficiency and minimises risk of liquid refrigerant entering the compressor.
Two of the most popular brands of screw compressor we use, Bitzer CS series and Hanbell RC2 series, both support variable load mode control, although these can also be applied for use on step control chillers and other systems.
Stable systems greatly extended compressor life For our own Re-Chill® projects we always prefer to apply the variable mode, in conjunction with Fan speed control, using either highly efficient and quiet EC Fans (electronically commutated) or Inverter
variable speed / frequency drives.
By applying the control strategy from a central controller, the entire chiller operation is orchestrated by one device enabling both efficient control and essential system safety features to work in
harmony. Not only does this reduce power consumption, optimised compressor control also means fewer stop start cycles, further reducing power spikes and reducing
Two – five year warranty packages are offered for our Re-Chill® Projects because of the confidence we have in the mode of control we routinely apply – Electronics with Variable compressor load control.
The Future Direct speed control of the compressor is the next development for Re-Chill® and we await with interest the level of further benefi ts such technology will provide our clients.
Modern modes of control can be applied to virtually any chiller and, when linked with other agesystem upgrades, can emulate the efficiency of much current, new equipment but at a fraction of the price.
For further information contact Thermagroup
Tel: +44 (0) 1623 758777
Fax: +44 (0) 118 956 0039
or visit their website http://thermagroup.com