Paul Hampton, engineering manager for the plant, says: “An energy appraisal by IDS produced a detailed list of all the motors on site and flagged up two glycol pumps that could save particularly high amounts of energy. We look for a payback of under a year and these applications met that criterion.”

An ABB drive was selected on one glycol pump in each refrigeration circuit, one of 55kW, the other of 11kW. The circuits are in constant operation, with the VSD controlled pump motor running 98% of the time. The direct-on-line pump is run for the other 2% of the time to ensure it remains in running order ready to take over the load if the main pump suffers a breakdown.

The VSD controlled pump motor is operated at 40Hz, producing a saving of 25% of the original energy usage. This equates to a payback time of less than a year, meeting Saladworks’ target.