Single vs Dual-Compressor Ultra-Low Temperature Freezers

Choosing the right ultra-low temperature freezer for your needs is always a tough decision.

With all the factors that need consideration, the choice is yours on whether to go with a single-compressor or dual-compressor system.

While a dual-compressor system might sound like it has some real advantages, there are still pros and cons to both options.

What’s The Difference Between Single and Dual Compressor Freezers?

A single compressor ultra-low temperature freezer utilises a single cooling cycle, much like a regular household freezer. Below are some examples of freezers using a single-compressor system:

A dual-compressor system on the other hand, houses two compressors. The cooling process works in a cascade system with two vapor compression cycles. One cycle is a low temperature cycle while the other is a higher temperature cycle.

In the first cycle, heat is removed from the space to be cooled, then the heat is rejected into the second cycle. The temperature difference between the first cycle condenser and second cycle evaporator allows the process to achieve ultra-low temperatures. After the second cycle, the heat is then released into the atmosphere. The cycling of low and high temperature compressors allows the setpoint temperature to be maintained.

In a dual-compressor system, each compressor will use a different refrigerant, with R23 commonly utilised on the lower temperature side, and R404a or other traditional refrigerants for the higher temperature side.

Here are some examples of dual-compressor system Ultra Low Temperature freezers:

On the other hand, a “dual-compressor system” may also mean a unit that houses a second backup compressor. There won’t be a cascade system but the second compressor will act as a failsafe to keep the freezer running if the first compressor fails.

Depending on the manufacturer, some cascade systems can also have each compressor function as a backup to the other though it might be limited. Once a compressor fails, the freezer would still be able to maintain a low temperature but most likely outside of the ultra-low temperature range.

Pros and Cons of a Dual-Compressor Ultra-Low Temperature Freezer

One of the leading pros of having a dual-compressor system is the increased lifetime of the unit.

A single compressor can run hot, increasing wear and tear and reducing the lifespan of the freezer. Dual compressors share the load, which prevents overheating, limiting wear and tear, and prolonging the lifespan of the freezer.

Another pro of dual-compressor systems is that one compressor can continue working independently should the other one fail.

In single-compressor systems, compressor failure would mean the freezer would be unable to stay cool at all. In comparison, a compressor failure in a dual-compressor system would not result in such catastrophic consequences but may allow the freezer to maintain a temperature around -40°C depending on the manufacturer’s design.

Energy efficiency in either single or dual compressor systems is debatable as manufacturers can claim that their models have superior energy efficiency. However, design advances in recent years means that both systems can be nearly equal efficiency-wise depending on how the unit was designed.

Alternatively, dual-compressor systems may come with some drawbacks like higher noise levels with two working cycles instead of one. Even then, with the right design build, the noise level of both systems can be effectively minimised.

And lastly, while dual-compressor systems may be priced slightly higher than their single-compressor counterparts, the cost of the unit is weighed against its extended lifespan which balances out to be more economical in the end.