Foodworks Australia Management


Case Study Super market refrigeration

  • Installed 22kw VSD on 18.5Kw motor after 2 months baseline recording of power consumption of the total total refrigeration switchboard (mid and low temp rack + all cases and condensers).
  • We programmed the drive to work with a Programmable Logic Controller linked to the refrigeration management system based on the system pressure required.
  • The Drive was programmed to run above normal speed of 50Hz up to 60Hz to accommodate peak demand and prevent compressor 2 and 3 cycling on as often.
  • We also programmed the drive to idle down to around 30Hz to maintain constant pressure and prevent Compressor 1 from cycling off.
  • Preventing compressors cycling on and off is one key energy saving measures. Start up load can be 5-7 times normal operating load.
  • The VSD controlled the motor perfectly supplying constant pressure.
  • Readings showed the pressure ranges in the system were much narrower.
  • Harmonics at certain frequencies caused some excessive vibration –those frequencies were identified and removed in the ramping process. •
  • Plumbing needed to be reinforced after it was identified that a weak point could be a problem

• 1200Kw per day = $166 • 35,500Kw per month = $4,970


• 960Kw per day = $134 • 29,500Kw per month = $4,130

Based on average charge of 14 cents per Kwh from July electricity bill.

Savings 9 months of the year of around $850 per month •

Summer months will be less but still measurable •

Annual saving in excess of $9,000 per year per rack. • Return on investment just over 12 months.