"Digital','Variable Capacity' Buzz Words
February 19, 2007
DALLAS - When the new compressor products at the 2007 International Air-Conditioning, Heating, Refrigerating Exposition (AHR Expo) are identified as scrolls, semi-hermetics, discus, screws, recips, and rotary, you realize that variety remains the theme of the sector. But the latest generations of those familiar technologies have more emphasis than ever before on digital and variable-capacity options.
Variable-capacity solutions included what was said to be the first commercially available variable-speed scroll compressors of their kind for light-commercial and commercial air-conditioners (rooftop units and chillers), according to Mogens Rasmussen, application development engineer at Danfoss Refrigeration & Air-Conditioning, North America (www.acr.danfoss.com). In addition, Danfoss has developed dedicated speed drives, control, and electronic expansion valves as part of the “total integrated solution,” he said.
“Our variable-speed compressors have an operating range from 30-90 Hz, addressing design capacities from 4-37 tons with R-410A refrigerant,” Rasmussen said. “In addition, complete variable-capacity solutions offer many integrated functions such as a built-in crankcase heater, motor protection, reduced start-up current, and protection against voltage fluctuation.
“For OEMs, the key benefits are the highest energy-saving performance at the lowest system cost and optimal system control, including exact load matching. For end users, benefits include increased comfort, lower utility bills, less downtime and noise, and lower maintenance costs.”
Variable-speed compressors can also be combined with fixed-speed compressors to form a hybrid solution, according to the company. By combining a single, variable-capacity compressor with one or more fixed-capacity compressors, an OEM design engineer can provide continuous variable capacity over 100 tons or more, resulting in decreased system costs, Rasmussen said.
“What’s more, the Danfoss variable-capacity compressor allows engineers to design compact light-commercial and commercial units with fewer manifolds.”
Emerson Climate Technologies (www.emersonclimate.com) announced its latest product, the Copeland Discus Digital™ compressor. The line offers “capacity modulation never before seen in reciprocating compressor applications and is available for a range of discus compressors from three to six cylinders,” the company said.
Offering continuous modulation from 10 to 100 percent, Discus Digital provides the ability to match capacity to the desired load of refrigeration equipment. This reduces the suction pressure and temperature variation of the refrigerated space and provides a decrease in compressor cycling rates, therefore improving compressor reliability, the company said.
Introducing Copeland Discus Digital into a refrigeration system also allows the system to match the capacity being generated to the required load, providing the opportunity for the system to operate more efficiently, resulting in optimum system performance and control, it was noted.
“The compressor delivers an ability to control temperature that end users have never experienced,” said Kurt Knapke, supermarket market manager, Emerson Climate Technologies. “This level of modulation is tailor-made for temperature sensitive applications and for improving the modulation capabilities of multiple compressor systems by bridging the gaps between the capacity steps of the fixed-capacity compressors. Therefore, the capability of Copeland Discus Digital reduces compressor cycling, improves compressor reliability, and improves system efficiency.”
Also noted was Copeland Scroll Digital technology that was said to provide infinitely variable capacity modulation for commercial applications with widely varying loads and a need to maintain precise temperature and humidity control.
It offers a way to modulate the capacity of the compressor from 10 to 100 percent, so that the output precisely matches the changing cooling demand of the room, and it does this without changing the speed of the motor.
Screw compressors were the focus of Hanbell (www.hanbell.com). Featured at the exhibit booth was a RC-13, compatible with a range of refrigerants. Sound reduction was another key. The RC-13 model had an overall dB(A) of 78.4 when using R-22. Models ranged from RC-10 to RC-24 and dB(A) from 73.1 to 91.2.
Tecumseh (www.tecumseh.com) unveiled a scroll design that it said “advances beyond yesterday’s compliant technology.” The VSA scroll came with a three-year OEM warranty and two-year wholesaler warranty.
“Our variable-speed design is the most efficient available,” the company claimed. “Rapid prototyping enables us to match unique design conditions.”
Also new from the company in compressor technology was what the company said was “advanced small reciprocating technology for refrigerators, freezers, and CO2 applications.”
The THK and TPB compressors were targeted for refrigerator and freezer applications with high efficiency and low sound. The TP, AK, and AJ commercial compressors were said to be for tough applications.
Regarding CO2 as a refrigerant, the company said it had prototypes available for 1/3- to 1/2-hp applications.
And, the company said, “A new horizontal rotary offers advantages in top-mounted display designs and space-saving, bottom-mount designs.”
OIL REGULATORA compressor-related product introduced at the expo was an oil regulator from Westermeyer Industries (www.westermeyerind.com). “It was designed to provide a single solution for multiple applications,” the company said. “The RG-4’s universal flange allows direct mounting to both Copeland and Bitzer compressors without adapter kits.”
The project controls oil levels in the compressor crankcase with a float-operated valve. It is adjustable from 1/4 to 1/2 sightglass and can operate with pressure differentials on 5 to 90 psig, with a maximum working pressure of 450 psig.
The company also said that for compressor configurations beyond Copeland and Bitzer, the kits could be used in converting the flange to nonstandard mountings.
Publication date: 02/19/2007