LITCHFIELD PARK, Ariz. - Carbon dioxide (CO2, R-744), once a refrigerant of interest overseas (primarily in Europe), has landed recently with a number of solid footholds in the New World.

After first gaining a presence in conjunction with ammonia in industrial refrigeration, it gained further ground this past summer in a commercial refrigeration system in a Georgia supermarket. Shortly after that it was given a good deal of attention at the 27th Annual Food Marketing Institute Energy & Technical Services Conference when presenters spent more than an hour looking at the refrigerant’s potential in supermarkets.

One of those presenters was Jens Christian Callesen, sales manager for Danfoss, who said much of the motivation for using CO2, which is a hydrocarbon (HC), is because of the heavy taxation on HFCs in such countries as Austria, Denmark, and Norway due to global warming issues.

He noted that CO2 is not a taxed or regulated refrigerant, it’s comparatively inexpensive, and it “can provide excellent energy efficiencies with lower operating costs.”

Some of the approaches being used today, he said, involve a combination of CO2/R-404A in cascade systems with the low temp using direct expansion and the medium temp with a flood-ed pump circulator; CO2 with R-410A in a cascade system with direct expansion on both the medium- and low-temp sides; and CO2 with R-1270 (propylene glycol) with direct expansion in low and medium temp and two pressure vessels instead of compressors.

The next frontier, Callesen said, is using CO2 in transcritical situations where it doesn’t have to be paired with other refrigerants. Callesen said, “Components exist and there are now prototypes.”

HFCS FOR A/C

Over on the air conditioning side, one HFC was getting special attention when it came to commercial rooftop applications. During the conference, R-410A was promoted as strongly on the commercial side as it has been in residential.

When it comes to looking beyond HCFC-22 in the 3- to 50-ton rooftop range, several HFCs were considered in regard to efficiency, safety, cost, availability and heat transfer, said Mike Walter, product manager, Commercial Refrigeration Units, Lennox.

He said R-407C came close to matching R-22 but had a temperature glide “resulting in some system issues.” R-134a with high displacement was shown to work well in larger systems, but not in the 3- to 50-ton range, he said.

So, like their counterparts in residential air conditioning, the commercial sector has zeroed in on R-410A for its good efficiencies as well as comparative ease in recovery and reclamation. The fact that the refrigerant is also being used by at least 25 OEMs added to the endorsement, he said.

He noted those working with the refrigerant have to deal with pressures twice as high, more serious moisture issues than with R-22, and with synthetic rather than mineral oils. Technicians will need the right gauges, recovery equipment and leak detection products, he said.

But the move to R-410A in a/c is a challenge supermarket technicians appear willing to embrace.

Lee Churchill, vice president, Seasons-4 Inc., noted manufacturers are custom-building R-410A systems for supermarket HVAC, because “supermarket clients are not shy about diving into new refrigerants,” he said.

Publication date:01/15/2007