Wheeler On HVACR: New HVACR Technology - Compressors
In last month's issue I covered some new HVAC equipment technology that I noted at this year's Air-Conditioning, Heating, Refrigeration Exposition, which was held in Anaheim, Calif., last January. I noted that there are also some interesting innovations in compressor technology that we should consider.
The most interesting (at least for me) is a new scroll compressor in the residential size range that Copeland has come up with. What is different about this compressor is that the design allows for multiple changes in operating capacity at a much lower cost and using a simpler design than we have seen in the past. This makes it possible to come up with far more efficient air conditioners and heat pumps at a lower price than ever before, and it allows for some important potential design changes in HVAC (and HVACR) equipment.
What Copeland has done is to install a 24V valve on the scroll compressor that, when it is activated, pushes the two halves of the compressor section apart, and this causes it to stop pumping. This is possible for Copeland due to its patented “Compliant Scroll” design. No compressor motor stopping, starting, reversing, or frequency changes are required. All that is needed is a small electronic circuit or a pressure switch to momentarily disable the compressor section when less capacity is needed. Theoretically, this technology can create an infinitely variable capacity compressor, which will make cooling systems and heat pumps more comfortable and more efficient.
In last month's issue I discussed some new equipment technology that allows up to eight different airhandlers to be operated from a single-compressor condensing unit. And having worked as national training manager for a Japanese HVAC manufacturer in the past, I can appreciate the enormous potential for change in our market that such innovation can bring. However, the system that I described currently uses a variable-frequency motor drive to reduce the compressor capacity, which adds significantly to the cost. Can you see what this lower-cost innovation can do for such a product? I certainly do, and that equipment manufacturer (Fujitsu) is already using compressors from Copeland. So, what can the future bring?
Another compressor manufacturer that has been a bit slower to enter the scroll-compressor market is Bristol. However, the company now has its own scroll that is a bit different from what I have seen in the past. The compressor section appears to be made of much thicker molded steel, which Bristol claims makes it quieter and creates less heat transfer than traditional designs. But Bristol is also improving its reciprocating-compressor lines to make them quieter and more efficient than ever before. Mufflers have been added internally to both the discharge and return sections, so they now rival the offerings that we have come to expect from Asian compressor manufacturers. The product manager didn't want me to overlook that.
When it comes to what is new in refrigeration compressors, I was particularly interested in a new hermetic CO2 compressor from Danfoss. In a time of environmental phaseouts of CFCs and HCFCs and rising refrigerant prices, inexpensive and environmentally-safe CO2 becomes an extremely attractive refrigerant alternative, especially in the commercial-refrigeration field. In fact, according to the press release, Coca-Cola has been actively involved in developing this technology.
The nice thing about CO2 is that it isn't toxic and it works well as a refrigerant. Danfoss says its CO2 compressors “use significantly less energy than compressors of like capacity using HFC refrigerants.” However, it has a relatively low “critical temperature,” which means that it will probably never be practical for use in standard air conditioners. So, time will tell.