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Variable speed shows 29% saving in freezer tests

USA: Variable speed Embraco compressors are said to have shown a 29% energy saving in comparative trials with fixed speed units in Hussmann retail freezers.

In addition to the energy savings, the study on Hussmann two-door and three-door grab and go freezers running on R290, also exhibited less variation in product temperatures.

On the three-door freezer, two Embraco NT fixed speed compressors were replaced by two FMFT variable speed units, resulting in 29% energy savings and 13.5% less variation in product temperatures. 

“The two variable speed compressors were able to provide the same cooling capacity of the previous two fixed speed models running on lower speeds most of the time, thus delivering such high energy savings,” explained John Prall of Embraco North America, during his presentation of the results at at this week’s Atmosphere America Summit.

The other application was a two-door grab and go freezer in which an Embraco NT compressor was also replaced by an FMFT, showing a reduction of 19% in energy consumption and 35% less variation in product temperatures. “The variable speed FMFT, with 12.7cc of equivalent displacement, replaced a fixed speed of 22.4cc. Even with such a difference, the FMFT was able to deliver the same cooling capacity and promote significantly higher energy efficiency,” said Prall. 

The Embraco FMFT has a maximum displacement of 14.7cc, which is equivalent to a 20.5cc (60Hz) fixed speed compressor, due to its overdrive feature. It is also capable of operating in 110V and 220V. 

In both applications of the case study, the estimate of payback for end-users was put at two years. 

“Another gain comes from the temperature stability, avoiding the product shrinkage caused by ill-preserved food,” added Prall. “The variable speed compressor can overcome temperature variations caused by door-openings much faster than the standard on-off compressor models.”

In the case study, the devices were controlled by Embraco Smart Drop-In, a control logic software that simplifies the use of variable speed compressors and eliminates the need for a control unit in the cabinet, making the migration from fixed to variable speed more cost-efficient.

Hussmann has chosen the Embraco FMFT variable speed compressor for its new portfolio of variable speed applications, the MicroSC, which includes grab and go freezers, horizontal islands and bunkers.

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