U.S.-based OEM Hussmann will soon be launching air-cooled propane (R290) monoblock refrigeration units for walk-in cold rooms and freezers. The new self-contained MicroSC units will complement the manufacturer’s existing water-cooled MicroDS monoblocks, which were launched last year.

According to a study conducted by Hussmann and Embraco – the Brazilian manufacturer of the MicroSC and MicroDS units’ variable-speed compressors – the R290 monoblocks can reduce the lifetime CO2 emissions of cold rooms by up to 6% compared to traditional HFC-based alternatives.

Details of the study and the new MicroSC monoblocks were presented by Neil Monson, Director of New Technology Development at Hussmann, and John Prall, Applications Engineering Expert at Embraco ( brand of Nidec Global Appliance), during a Refrigeration Case Study session at the ATMOsphere (ATMO) America Summit 2023 on natural refrigerants. The conference took place June 12–13 in Washington, D.C., and was organized by ATMOsphere, publisher of Hydrocarbons21.com.

Future-proof refrigeration

Driven by the need to reduce refrigerant charge and improve energy efficiency, Hussmann’s subsidiary Krack has developed a series of low-charge, self-contained, variable-speed R290 monoblock refrigeration units for walk-in cold rooms.

The range is designed to replace HFC systems.

With a charge of less than 150g (5.3oz) of R290 per self-contained unit, Hussmann’s monoblocks sit well within current and future regulations on propane, explained Monson.

The small ceiling-mounted units fit easily within cold rooms and are simple to install, with customers able to have them up and running in less than a day, he said.

Krack and Hussmann have steadily been releasing the product range in stages over the last six months. They are currently offering three water-cooled models under the MicroDS range: a two-compressor unit for medium temperature (MT) and two- and four-compressor units for low temperature (LT).

The companies are about to release a two-compressor air-cooled MT unit under the MicroSC range and has plans to launch two LT models soon, he added.

MT units cover -2 to 10°C (28 to 50°F), while LT ones cover -26 to -15°C (-15 to 5°F).

According to a previous interview with Hussmann’s Senior Product Leader Ronald Grabowski, while the water-cooled monoblocks are generally better suited to larger retail stores (due to the need for a waterloop system), the air-cooled models will offer smaller retailers a more affordable alternative.

Lifetime emissions reductions

To test the advantages of using R290 monoblocks over traditional HFC refrigeration systems, Hussmann and Embraco conducted a study that analyzed a 20.5kW (5.8TR) dairy cooler and a 5.9kW (1.7TR) freezer.

In the study, the manufacturers compared an R448a-based system with seven MT and three LT water-cooled R290 monoblocks.

Over the course of the product lifecycle, which is estimated to be around 15 years, the study found that the MicroDS units reduced CO2 emissions by 6%, despite a slight increase in the energy consumption of the MT system.

For less than US$12 (€11) extra a month in energy costs, over 90 metric tons of CO2 can be saved, explained Prall and Monson. Savings were achieved by improvements in efficiency on the LT side, as well as direct emissions from the low GWP of propane.

According to Prall, the LT energy efficiency was achieved thanks to the load-matching ability of Embraco’s variable-speed FMF compressor.

“The 15cc compressor can overdrive to 5,000rpm when needed and then slow down to 1,600rpm to load match the system,” he explained. “The seven-inch [17.8cm] compressor can effectively deliver [1.5HP] of cooling. The idea here is it offer a more stable temperature within the cold room and then quickly return to temperature after doors are opened or following defrost recovery.”

“The idea here is it offer a more stable temperature within the cold room and then quickly return to temperature after doors are opened or following defrost recovery.”

John Prall, Embraco