A study showed that there was potential to reduce energy consumption by more than 30%. Installation of Liquid Pressure Amplification (LPA) and Inverter control of condenser fans was proposed to the direct expansion refrigeration systems.

The modifications allow the refrigeration system to be re-commissioned to operate at low discharge pressures, often referred to as floating head pressure, increasing refrigeration capacity while reducing absorbed power.

The LPA pump is installed into a manifold in the outlet from the liquid receiver; refrigerant is then pumped to the expansion valve, providing good quality liquid refrigerant to the expansion valve during low head pressure operation.

Inverter control of condenser fans allows the discharge pressure to be continually adjusted in relation to both external ambient temperature and cooling demand, to optimise energy efficiency for any given condition.

The design incorporates a number of safety features to ensure that no single point of failure could affect production.

Excalibur undertook an initial pilot installation to a Blast chill refrigeration pack fitted with 4 Copeland reciprocating compressors operating on R404a, with a capacity of 340kw, and a 10 fan air-cooled condenser. 

The refrigeration system was monitored prior to modification to establish a base line to compare performance. Installation was completed in July 2012 and again monitored to show the improvements in efficiency. An energy reduction of 36% was achieved, a cost reduction of over £25,000 / year and a return on capital of less than 18 months, with no detrimental effect on production.

The success of this project convinced the client that significant cost reductions could be achieved and Excalibur was instructed to modify a further five systems, which have demonstrated an annual cost reduction of over £79,000 and a return on investment  of less than 2 years.

Steven Pye, operations director at Wholesale Power UK, undertook energy surveys at the sites following installation and reported that the sites were delighted not only with the performance of the systems and with the associated reduction in consumptions, costs and emissions, but with the quality of the installations.