Variable speed drives from Control Techniques have helped slash energy bills by over $2,000 a month, reduce downtime and extend equipment life at a US food distribution centre. The savings have been achieved due to lower fan motor and compressor energy usage and better control of the site’s freezer/cooler systems
The food distribution centre facility is owned by one of the largest suppliers to the food service industry, and stores large quantities of foodstuffs in freezer and cooler boxes ready for regional distribution. Prior to Emerson’s upgrade work, each freezer and cooler box was controlled by a circuit with its own compressor, condenser and evaporator(s). These were in turn controlled by individual mechanical thermostats and defrost time clocks.
The customer was having an issue with the defrost performance of the evaporators on the freezers: all of the evaporators needed to be defrosted at the same time, but the freezer condensing units had individual mechanical defrost clocks that would not remain synchronised once set.
Key Mechanical, the customer’s refrigeration contractor, approached Emerson for help with finding a solution. Working alongside Emerson Retail Solutions, an Emerson Climate Technologies company, Control Techniques and Key Mechanical proposed new control systems for the circuits on the freezer and cooler boxes. The solution involved the installation of 21 Commander HSK variable frequency drives from Control Techniques and two Einstein E2 RX400 refrigeration controllers from Emerson Retail Solutions which control existing Copeland semi hermetic compressors from Emerson Climate Technologies.
The new system enabled the customer to control the speed of each Copeland compressor, and the condenser and evaporator fan motors. The RX400 controllers are programmed to control temperature, defrost cycles and frequency drive output for floating head pressure, floating suction pressure and evaporator fan motor speed during the normal refrigeration cycle. Of the 21 HSK drives, seven control the Copeland compressors, seven control the condensers and seven control the evaporators.
When the new system was installed, the result was a reduction in electricity consumption of 250,676 kWhr per year, providing a saving of over $2,000 a month on the customer’s energy bill. Energy savings were possible due to reduced fan motor energy consumption as a result of improved fan management, and a reduction in compressor energy consumption due to reduced compression ratios. Additionally, downtime has been slashed and overall equipment life has been extended due to better temperature control and defrost management as well as reduced compressor cycling.
Ron Kvinge, branch manager for Key Mechanical Portland said: “The only option for the customer, other than a drive retrofit was replacing all the rooftop equipment for the plant – which would obviously have been a much larger capital expense. The solution suggested by Key Mechanical resulted in better control of the freezer/cooler systems, major energy savings and less wear and tear on equipment.”
David Yankaskas, regional sales manager at Control Techniques, said “Without Emerson’s proprietary suction and head pressure controller technology, the energy and cost savings for our customer could not have been achieved.
“From the perspective of day to day operations, controlling the HSK drives through the two Einstein RX400 controllers is obviously much simpler than having to programme and monitor all 21 of them individually. Overall, the Emerson/Key Mechanical solution is functioning extremely well and is saving the customer over $2,000 dollars a month!”
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