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Success cascades down

The first R407F-CO2 cascade in France has achieved significant energy savings compared with the R404A system it replaced, reports the refrigerant’s distributor Climalife

The Intermarché supermarket in Trégueux, France has pioneered the use of R407F in cascade with CO2, and the retailer is pleased with the energy reduction the system has wrought compared with its predecessor system.

Honeywell, the developer of R407f, branded Performax LT, believes it is the right refrigerant to meet the needs of large and medium-size stores whose managers are looking to save energy.

Intermarché decided to increase the sales floor of the 2,225 sq m store, located in the region of Côtes-d’Armor, by more than 30 per cent to 3,000 sq m. Contractor Central Froid was engaged to replace the old cooling equipment that ran variously on R22, R408A and R404A.

Work began in late 2011 on a solution centred on an R407F-CO2 cascade installation, exploiting the environmental and energy benefits of R407F. 

As the store needed to remain open during the expansion, technical solutions were needed to ensure constant refrigeration. The operation therefore proceeded in several phases over four months, with four to seven technicians at a time working. The refrigeration installer recommended that initially a CO2/R404A cascade was installed, in order to be able to continue working with the existing linear compressors that used R404A, and then to systematically add the new refrigeration equipment.

Following a detailed study of needs, the system was designed around two central HK refrigeration packs, each equipped with variable speed drives in order to limit energy consumption and short-cycle starts, and to manage the compressors’ operation in order to best meet the needs of the various cold units. The Danfoss electronic expansion system is equipped with AKCC 550 and AKCC 750 controllers.

The CO2 low-temperature central unit consists of three Bitzer semi-hermetic compressors, which supply four linear compressors and two -25 deg C frozen chambers. The medium-temperature central unit, charged with 500 kg of R407F, includes four further Bitzer compressors and a floating HP, and generates cooling for 14 work rooms, the air conditioned premises, and 18 linear compressors. In the condensing section, a plate heat exchanger with power of 150 kW is installed to recover heat for the supermarket air heaters.

Once construction of the extended site had been completed, the R404A/R407F retrofit was carried out overnight, and completed in eight hours. The installation was fully drained, the R404A was retrieved in accordance with regulatory requirements, and the R407F injected via the installation’s liquid line. In order to avoid emptying the display cases, the installer recommended using dry ice. This measure also made it possible to avoid temperature increases and a resultant risk of CO2 leaks, due to the very high pressure of the fluid. Overheating adjustments were performed.

Close cooperation between Central Froid and Danfoss, Honeywell and Climalife proved necessary in order to configure the electronic control system, initially designed for R404A, to work with R407F.

This experience subsequently enabled control system manufacturer Danfoss to integrate this new refrigerant into its equipment. The same was true for Siemens, which was contacted for its Polycool expansion valve, which is installed on the CO2 evaporative condenser.

On-site operating readings were taken three months after service began. With more cooling units (12m more MT display case linear compressors; 10m more freezer linear compressors; three new air conditioned rooms and  pastry, fish and cheese counters), and a 30 per cent expansion of the store, the use of R407F still enabled the electrical bill for cooling to be reduced, the store reports

Absorbed current as measured with R407F is 10 per cent less on average than with the R404A. In practical terms, these energy savings match the theoretical estimated values. 

Already convinced of the performance of Performax LT’s from previous installations, Central Froid’s Mickael Rouxel was pleased with the results achieved using this new system. “This refrigerant is a reliable product that shows promise for the future. Since April 2012, we have been using it regularly and have had no negative feedback for the systems in service. No leaks have been found and there is no need to change the seals on the solenoid valves.”

The contractor feels it is his duty to remind end users ‘every day’ of the benefit of lower-GWP fluids to preserve the environment and offer more energy-efficient solutions. “After my years working in Switzerland, I know that we need to take care of the environment and make it an important part of our lives.”

* R407F will be one of the subjects debated at RAC’s New Refrigerants Question Time on May 24.

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