Visair Upright Refrigerated testing of Variable-Speed Driver
Marty Dunningham (FPG Refrigeration Design Engineer) testing the Visair Upright Refrigerated

November 2023

Recently eNews caught up with FPG refrigeration design engineer Marty Dunningham, to talk about Variable Speed Drives.

FPG eNews: FPG is re-engineering refrigerated cabinets with Variable Speed Drives (VSDs). What are they and what do they do?

Marty: A VSD also known as an inverter, is a device used to control the frequency of the electrical power supplied to a VSD-compatible motor depending on the demands of the system.

In a refrigerated cabinet, the compressor is powered by a motor to move the refrigerant through the refrigeration system. When engineering a refrigerated display cabinet to be VSD-enabled, the compressor incorporates an inverter to control the speed of the motor and hence the rate of refrigerant flowing through the refrigeration system.

With a standard compressor, the flow of refrigerant is constant regardless of cooling requirements. The inverter compressor controls the flow of refrigerant needed depending on the amount of cooling needed. This responsiveness means that the compressor increases the flow of refrigerant when the temperature needs to reduce. If less cooling is required, the compressor reduces the flow of refrigerant.

Inverter with VSD
Variable Speed Drive inverter compressor

FPG eNews: What are the advantages of applying VSD technology to refrigeration systems?

Marty: There are many benefits of using a VSD in a refrigerated display cabinet:

  • Energy Efficiency: With a VSD, the compressor runs continuously eliminating the high energy demand of starting and stopping the motor. The VSD also allows the compressor to operate at lower speeds during periods of lower demand, reducing energy consumption. This is particularly advantageous during off-peak hours or when the display cabinet is not fully stocked.
  • Temperature Control: The variable speed drive enables more precise control over the temperature inside the cabinet. This can result in a more stable and uniform temperature, ensuring that the displayed products are kept at optimal conditions.
  • Reduced Wear and Tear: Starting and stopping a compressor motor frequently can lead to wear and tear. With a variable speed drive, the compressor can ramp up or down gradually, reducing stress on the motor and extending its lifespan.
  • Adaptability to Load Variations: Refrigerated display cabinets often experience variations in load due to factors such as changes in ambient temperature, door openings, or restocking activities. A VSD allows the system to adapt to these variations by adjusting the compressor speed accordingly.
  • Lower Noise Levels: Running the compressor at lower speeds can contribute to reduced noise levels, which is particularly important in environments where a quieter operation is desired, such as retail spaces.

In summary, a VSD-engineered refrigerated display cabinet provides a more efficient and adaptable means of controlling the refrigeration system, offering benefits in terms of energy savings, temperature control, equipment longevity, and overall operational flexibility.

FPG eNews: Many of our customers are concerned about energy efficiency. Please tell us more about the impact that a VSD-enabled cabinet has on power consumption.

Marty: The energy efficiency saving can best be demonstrated in the two test charts below. In both cases Visair Upright Refrigerated R290 1000mm cabinets were tested in FPG’s test chamber with environmental conditions set for Climate Class 3.

The first chart shows the energy consumption of the cabinet with a standard compressor.

IN-VA10-Bxxx Energy Data

The second chart shows the energy consumption of the cabinet engineered with a VSD (an inverter compressor).

IL-VA10-B1xx Energy Data

You can see that the cabinet with the standard compressor uses more power than its VSD-engineered counterpart. This is also reflected in the Australia and New Zealand Star Ratings. Both cabinets are compliant, but the first cabinet achieved 2 stars while the VSD engineered cabinet achieved 3 stars.

FPG eNews: Anything further to add Marty?

Marty: I am still testing the Visair Upright cabinets with different combinations of components to see if further energy efficiency gains can be had, whilst still meeting compliance requirements.

We are also planning to introduce VSD technology to other FPG cabinets. We are waiting on the availability of R290 inverter compressors suitable for our smaller refrigerated cabinets. So watch this space!

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