When talk first surfaced a number of years ago about using R-744 (CO2) in commercial refrigeration, there were two challenges — making the refrigerant work as a stand-alone in transcritical applications as well as in cascade systems and developing the components to make such approaches possible.

Progress continues to be made on both fronts. Recent announcements from within the industry point to developments in compressors, heat pumps, and modular valves. Meanwhile, sites are up and running, smaller equipment is embracing the refrigerant, and training facilities are coming on-line to help technicians familiar with f-gasses deal with an old gas that is new to many of today’s younger refrigeration technicians.


In an announcement made in Europe earlier this year, Emerson Climate Technologies noted that it had started production of a line of semi-hermetic reciprocating compressors called Stream. They are 4- and 6-cylinder compressors for HFC refrigerants as well as R-744.

The company said the 4-cylinder compressors can be used for CO2-transcritical medium-temperature refrigeration applications. Stream is designed for medium temperature cascade and booster systems. The models have high side design pressure of 135 bar and come with frequency inverters. Refrigerant flow and heat transfer have been optimized. All compressors are equipped with CoreSense™ technology, an in-depth information system that monitors conditions within the compressor and proactively shuts it down to prevent damages.

Heat Pumps

Heat pumps were given a lot of attention at the HVACR Japan 2012 trade show, held in February in Tokyo. On display were heat pumps using R-744 for commercial applications.

Nihon Itomic Co. Ltd. had an 80-kW Eco-Cute CO2 heat pump water heater for commercial applications. According to the company, a Y-shaped configuration allows for 30 percent reduction in the installation space needed for the unit, while retaining a large capacity of hot water.

Mitsubishi Heavy Industries showed Q-ton, a commercial Eco-Cute featuring a coefficient of performance (COP) of 4.3. The unit uses a two-stage CO2 “scrotary” that is said to have high efficiency under every operating condition by means of a two-stage compression structure with a rotary compressor placed on the low stage and a scroll compressor on the high stage side.

Panasonic showed a large line of Eco-Cute models for commercial applications. In a modular approach, the company said the combination of up to four units typically used in residential units can serve light commercial applications.

Mitsubishi Electric displayed the commercial Eco-Cute (model QAHV-N560B) that the company said can achieve a COP rating of 4.1 thanks to an inverter-type scroll CO2 compressor.

Mayekawa featured the EcoSirocco CO2 heat pump that the manufacturer said is able to generate the hot air needed in industrial drying or heating purposes. The company also showed the Unimo air-to-water CO2 heat pump with a COP of 4.2 for mid- to large-size facilities such as hotels, hospitals, and food processing plants.

Hitachi showed a light commercial (15-kW) Eco-Cute model, adapted to hard water conditions from wells.


In an announcement made in the March 5 online publication R-744.com, Danfoss reported that it has an improved function module for its ICM/ICS modular valve concept — a ready-made insert key to determine the capacity of the valve: “It is now possible to exchange the wearing parts, instead of the whole module.”

The announcement also noted, “The common valve body for ICS and ICM is available in several different connection sizes, while different function modules offer a range of capacities and functions. All ICM and ICS control valves are designed and tested to withstand a maximum working pressure of up to 52 bar (750 psi) making them all suitable for the natural refrigerants CO2 and ammonia.”

The new function module was created in response to customer requests. “As a result of damage from dirt or welding particles in the system during start-up, customers requested that it should be possible to exchange the Teflon seat in the function module,” R-744.com reported.

Danfoss announced that “this is now possible thanks to a modification in the function module that allows the whole size range from 25 to 150 to be serviced with a dedicated spare parts kit.”

On Site

One of the more recent announcements concerning expanded use of R-744 in transcritical applications was from the Carrefour Group, which said it plans to phase out the use of HFC refrigerants in all of its refrigeration equipment by 2015.

The manufacturer installed its first CO2 transcritical refrigeration system in a hypermarket in Burolo, Italy. Overall, the company said it is testing 18 sites using natural refrigerants in France, Italy, and Turkey.

At the Burolo store, both the refrigeration units and freezer units use R-744. The manufacturer said the quantity of CO2 needed for refrigeration units is approximately one-third less than the refrigerant charge required by a conventional system and the energy efficiency of refrigeration units is up by 15 percent. The company said the new technology should be extended to one or two additional sites by 2012. A large-scale rollout is planned for 2013, according to the company.


The issue of how to properly train technicians familiar with f-gas refrigerants to begin working on equipment with R-744 is being addressed on a number of fronts.

One of those is the Bitzer Brazil CO₂ Technology Training Center, which has scheduled courses in a variety of languages. It promotes R-744 technology, and this year is also adding training in ammonia and HC refrigerants.

Topics include safety, design, installation, commissioning, service, and maintenance. The courses at the center cover a range of topics including safety issues, design features, installation, commissioning, servicing and maintenance procedures, and include both practical and theoretical classes. They are targeted for engineers, system designers, installing technicians, operators, and others interested in the use of the refrigerant.

The remaining course dates for 2012 are Aug. 6-10 and Oct. 22-26, both taught in Portuguese. The site is the Senai Oscar Rodrigues Alves School in Sao Paulo, where performance testing for refrigeration systems and condenser units will also be held.

The HC (hydrocarbon) and ammonia courses will cover use of the refrigerants in supermarket facilities in the high stage system, as well as the recent release of screw and scroll compressors for the refrigerants.

According to the online publication R-774.com, “The CO2 Technology and Training Center features three refrigeration racks with modern semi-hermetic compressors of the Octagon series in parallel application, used at medium and low evaporation temperatures. There are also three cold rooms, two medium-temperature (cooling and walk-in cooler) and one low-temperature (freezing) room. Installed in each cold room are the evaporators (air coolers) of their respective racks. In addition, there are also two low temperature islands, which are linked only to the CO2 rack. There is also a CO2 rack in the transcritical condition and another one using CO2 and ammonia in the subcritical condition.”

Publication date: 7/2/2012