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issue: April 2005 APPLIANCE Magazine

Compressor Technology
The Efficiency Workhorse


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By Lisa Bonnema, Editor

Although there are several ways air-conditioning and refrigeration OEMs are meeting today’s efficiency demands, compressor manufacturers are working feverishly to design low-cost, high-performance products that exceed market expectations.

World Production for Air-Conditioning Compressors in 2003. Source: BSRIA Worldwide Market Intelligence

It’s fairly safe to say that compressor technology, while mature in its basic function, is constantly changing. From new efficiency requirements to constant refrigerant phase-outs, this is one supplier category that will never be short of work. And let’s not forget about noise: high performance, yes, but it better be quiet.

Fortunately, the industry’s top suppliers have done their homework, and a little extra credit for that matter. Take the upcoming air-conditioning efficiency switch to 13 SEER as an example. While compressor makers recognize the need to do their part on the efficiency side, some have had the foresight to design for the additional effects the new regulations will have on their OEM customers.

“After the 13 SEER regulations take effect, it will be harder to differentiate equipment on efficiency alone,” notes Frank Landwehr, vice president of marketing for Copeland Air Conditioning, a division of Emerson Climate Technologies (Sydney, OH, U.S.). “Other differentiating features will be essential to the OEM’s ability to offer more value to the homeowner. Recent innovations in compression technology are helping customers offer this additional value.”

Emerson Climate Technologies says its Copeland Scroll UltraTech™ compressors, for example, are designed to increase system efficiency, but also reduce humidity, making it a great option for manufacturers that want to offer humidity control as a value-added feature.

These and other technology updates are giving air-conditioning and refrigeration OEMs all the right tools to make their equipment as efficient, quiet, and reliable as possible.

Rheem partners with compressor manufacturers like Copeland and Bristol for high-quality, efficient, and dependable compressors for its full-line of condensing units and air-conditioners. Pictured is Rheem’s Prestige Series® air-conditioner, which uses a Copeland Scroll compressor.

Energy Updates

It’s no secret that the energy eater in any air-conditioning system is the compressor. So when the U.S. government required units to be 13 SEER by 2006, OEMs looked to their compressor suppliers for help.

According to Gary Bedard, vice president of Residential Product Marketing Manage-ment at Lennox International (Dallas, TX, U.S.), there are a couple of ways OEMs are attacking efficiency in the HVAC market. “You can make the heat exchanger surface more efficient, which basically adds more copper and aluminum. Or, the items that use electricity can be made more efficient themselves,” he tells APPLIANCE. “For compressors, this can be done by increasing the efficiency of the mechanical parts of the compressor or by simply making the motor that turns the compressor more efficient. Compressor suppliers are really doing both to help manufacturers address the 30-percent increase in minimum efficiency levels by 2006.”

For Emerson Climate Technologies, the answer was releasing a new version of its Copeland Scroll™ compressor designed specifically for the new guidelines. “With this significant industry event, scroll compression technology will be increasingly important to the U.S. market,” Mr. Landwehr tells APPLIANCE.

The new design, which won an Innovation Award at this year’s AHR Expo, is said to be 7-percent more efficient and 30-percent lighter than the prior version. To create the new compressor line, Emerson says its engineers made 20 design improvements, including an optimized scroll and seal design for improved efficiency, common shell/tube configurations and standardized parts for improved manufacturing and product quality, improved temperature protection, and a larger shaft bearing system for enhanced reliability. The unit is also 4-dBa quieter, according to Mr. Landwehr, thanks to a new quiet shut-down solution and a redesigned shell.

Rheem Air Conditioning (Fort Smith, AR, U.S.) attributes some efficiency gains to developments in two-stage compression and tighter manufacturing tolerances. “The two-stage compressor is another development that advances energy efficiencies because most often, it operates at a low speed (first-stage), and shifts to second-stage only during high-load conditions,” explains Tim Hawkins, residential air-conditioning engineering manager. “In addition, refinements in compressor technology include tighter manufacturing tolerances for steel laminations and copper winding materials and other technologies that maximize efficiencies while reducing costs.”

In commercial refrigeration, Danfoss (Baltimore, MD, U.S.) says variable-speed technology is
gaining popularity due to demand for greater refrigeration system efficiency and compliance with energy legislation pending in several U.S. states. As a result, Danfoss has introduced an a.c.-operated variable-speed hermetic compressor, type NLV, in 1,400, 2,000, and 2,600 BTUH versions.

The NLV units use a specially designed electronic control and optimized mechanics that allow a speed range of 2,000 to 4,000 rpm. According to Danfoss, the feedback loop from the temperature control, combined with self-learning logic in the electronics, allows the compressor to automatically match the appliance’s load requirements with optimum speed, ensuring minimum energy consumption. This means that when cooling requirements change, like when a refrigerator door opens or contents are added to the cabinet, compressor speed is automatically adjusted to save energy. This is an improvement over single-speed compressors, which cycle frequently and can result in large variations in cabinet temperature and hence, energy inefficiency.

Danfoss has added a new higher capacity direct current hermetic compressor, type BD80F, to its product offering. The compressor is designed for greater energy efficiency in mobile applications, including refrigerated cabinets for small delivery vans and larger refrigeration systems on boats and homes off the power grid.

Reciprocating Advancements

Some industry professionals have proposed that reciprocating technology, which has commonly been used for its simple, low-cost design, will be outdated with the new 13 SEER minimum, leaving scroll as the leading technology. Bristol Compressors (Bristol, VA, U.S.), which makes both reciprocating and scroll compressors, doesn’t believe this is always the case. “No one compression solution is optimal for all applications,” Scott Hix, vice president of product engineering, tells APPLIANCE. “We believe that in applications of about 3.5 tons and below, the reciprocating [compressor] is the best solution and in larger tonnage systems, the scroll is the best choice.”

According to Bristol, with the lower condensing temperatures and higher evaporating temperatures seen in the new 13 SEER systems, modernized reciprocating compressors are more efficient than scroll units at capacities less than 3.5 tons. The company notes that while scroll compressors have higher volumetric efficiency, reciprocating compressors have superior mechanical efficiency. This, it says, is because reciprocating products are less affected by friction, losing 23-percent less power to friction compared to a scroll unit.

Bristol also says volumetric efficiency is important because at lower condensing temperatures, the mass flow from reciprocating compressors will be higher than that of a scroll unit for equal system rated capacity. This, the company admits, results in some reduced system efficiency that must be made up in higher compressor efficiency, which Bristol claims has been accomplished with recent advances in reciprocating technology.

According to Mr. Hix, one example is Bristol’s new H2IJ Benchmark reciprocating compressor, which features advancements in both efficiency and sound technologies. “The compressor operates in either one or two cylinder modes by simply reversing the direction of motor rotation,” he explains. “With a displacement reduction of 60 percent (about 50-percent actual system capacity), this technology is able to run longer in the low-capacity mode, with fewer start/stop cycles. The result of this is that humidity can be maintained at lower levels, air stratification is reduced, and the indoor blower can be run at lower speeds, resulting in lower indoor sound levels.”

To further reduce compressor sound, the shape of the H2IJ’s shell was designed to minimize compressor sound radiation. The unit also utilizes a patent-pending, internal suction muffler that reduces pressure pulsation inside the shell.

Refrigerant Developments

As U.S. air-conditioning manufacturers aggressively design new 13 SEER products that meet the 2006 efficiency regulations, compressor suppliers are working hard as well. Copeland has developed a next-generation Copeland Scroll™ platform to help its OEM customers reach 13 SEER. With 20 major design improvements, the product is said to deliver up to 7 percent more efficiency and is 4 dBa quieter than the previous version.

With the R22 phase-out coming up in 2010, HVAC companies are starting to design products with new refrigerants, mainly R410A. “The performance of R410A has proven to be more efficient than the current R22 refrigerant, so the bulk of redesign focus by York and our compressor manufacturers has been with R410A,” says Cos Caronna, senior director of Engineering and Product Management at York UPG (Wichita, KS, U.S.). “However, we are not losing sight that there are still 4 more years of production with R22, and York plans to be competitive in both areas.”

Rheem Air-Conditioners is taking the same approach. In fact, the company says its contractor customers still prefer R22 refrigerants. “We’ll continue manufacturing these products until the 2010 transition date,” Mr. Hawkins tells APPLIANCE. “Our goal is to have the products that contractors need when they need them.”

Mr. Bedard of Lennox believes that acceptance of R410A will grow as the industry transitions to the higher efficiency products, which can handle the new refrigerant better.

One future alternative that several compressor makers are looking into is CO2 because of its environmental benefits. The refrigerant is already being introduced in regions like Europe, where there is discussion of banning HFC refrigerants all together. And while this green refrigerant may still be new to the North American market, it is a very real option for many global manufacturers.

Tecumseh Compressor Grup (Tecumseh, MI, U.S.) has been working with CO2 technology for several years and introduced its new EPACO2OL product at this year’s AHR Expo. Although the CO2 compressor won’t be commercially available until 2006, William J. Merritt, Jr., vice president of sales and marketing, says units are currently being field-tested around the world. In fact, Tecumseh has been supplying the U.S. military with CO2 compressors for heat pumps and air-conditioners throughout the last 3 years.

“CO2 is something that has really been driven from the green standpoint,” Mr. Merritt tells APPLIANCE. “I think a lot of the people in North America haven’t addressed it because they are driven more by North American business opportunity first. We looked at this really from a global perspective, and the global demand is for more green refrigerants that can be used everywhere in the world.”

Some companies in North America, however, are leading the charge toward the environment-friendly refrigerant. Mr. Merritt says corporations like Coca-Cola and McDonald’s are partnering with their equipment suppliers on CO2 initiatives. Possible applications, he says, include 1/5- to 1-hp refrigeration products like beverage coolers and ice makers, as well as heat pumps and hot water heater applications.

Tecumseh plans to offer its EPACO2OL product in both reciprocating and rotary versions that will also be available as part of a complete refrigeration system. Mr. Merritt says that although CO2 compressors in themselves aren’t quite as efficient as HFC units, Tecumseh is making up for that in system components, creating an overall refrigeration system that is as efficient or more efficient than current models.

ACC Compressors has also been researching CO2 over the years and plans to offer a CO2 compressor by 2005. The Italian company has spent a lot of R&D time attacking the challenges of making CO2 an efficient, cost-effective option for OEMs.

According to ACC, challenges of working with CO2 include very high pressures (above 100 bar) and the need for a transcritical cycle. The company explains that the critical temperature of CO2 is as low as 31ºC, which means that no condensation is possible above that temperature. In addition, the CO2 cycle is more sensitive to suction temperatures than HC and HFC cycles, and discharge temperatures can also be high. Because CO2 volumetric capacity is very high in comparison with HCs and HFCs, displacements are much smaller. According to ACC, the high pressure differences between compressor discharge and suction force the use of two-stage compression for low back pressure (LBP) appliances and imaginative mechanical solutions. ACC says it is successfully overcoming that challenge with some patent-pending solutions.
Even with several compressor designs in the works around the world, Mr. Merritt of Tecumseh admits that CO2 technology is still in its infancy and will most likely be a niche product. “It is not going to dominate the market,” he says. “It will just be another option, but a green one that will work for all locations.”

The Bigger Picture

While the majority of HVAC suppliers and OEMs in the HVAC/R industry have addressed the basics of quality, Mr. Bedard of Lennox says OEMs need to look at quality on a larger scale, including after the unit has been installed. This is the main reason Lennox decided to offer Copeland’s Comfort Alert system as a product feature. The on-board diagnostics system, which was designed to work with Copeland Scroll compressors, helps installing contractors identify problems in the field.

“Misdiagnosis makes up a surprising number of the compressors that are changed during servicing,” Mr. Bedard says. “No one is happy with this arrangement—it doesn’t solve the consumer’s problem and the contractor wasted valuable technician time in the summer months. The Comfort Alert helps to correctly identify when the compressor is the cause of the problem and when it might be something else.

Mr. Landwehr adds that the Copeland diagnostics system is also one more way OEMs can differentiate themselves, making the contractors job easier and the customer’s experience with a service call that much more enjoyable. Mr. Bedard seems to agree. “In the long run,” he says, “this keeps a customer satisfied.”

 

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