When variable-speed multi-split technology made its way into the HVAC market, manufacturers and contractors alike searched for valid methods to compare and market the new energy efficiencies. Without a test procedure to certify the claims of the manufacturers, comparing apples to apples proved difficult.
To fill the void of a valid performance test for this equipment, the Department of Energy (DOE) began working on new procedures in 2007 after releasing an amendment to the Uniform Test Method for Measuring the Energy Consumption of Central Air Conditioners and Heat Pumps (10CFR 430 Part B), that included specific test requirements for multi-split variable-speed systems.
With the help of the National Institute of Standards & Technology (NIST) and input from the industry, the DOE created a test procedure designed specifically to compensate for multiple combinations of the equipment and issued a mandate making the new procedures and ratings effective April 21, 2008. In response to the new mandate, AHRI adopted the new test procedure into its 210/240 standard and created a separate listing for certified variable-speed multi-split heat pumps and air conditioners in the AHRI product directory.
REDEFINING PROCEDURESThe need for new procedures is not an unusual issue in the multi-split variable-speed arena. “The existing test procedures did not reflect the real potential of the new multi-split variable-speed equipment,” said Roy Kuczera, senior vice president of sales, HVAC Products, Fujitsu General America Inc., Fairfield, N.J. “Manufacturers of these types of systems appealed to the DOE about the efficiency limitations that existing standards created for variable-speed type equipment.”
During this time, the AHRI-1230 draft was under development by the Ductless Equipment Section’s Engineering Subcommittee, which, according to Kuczera, would have fully showcased the systems’ efficiency.
“The DOE chose not to wait for the development of AHRI-1230, however, and instead began working on amendments to the existing AHRI 210/240 test procedures,” he said. “While the variable-speed testing procedure provides a temporary solution, AHRI-1230 would provide a solution that would allow ductless manufacturers to demonstrate the complete efficiency of these products.”
With previously issued equipment waivers expiring, the DOE pushed up the timetable and began the creation of new procedures. According to Lee Smith, director of Product, Engineering & Applications at Daikin AC (Americas) Inc., Dallas, there were three specific challenges that arose during the development of the testing and rating language for variable-speed multi-split equipment. The first was “quantifying the means of rating systems with almost infinite combinations.” The DOE resolved this issue by crafting a detailed definition for a tested combination. In essence, a multi-split system with multiple indoor coils possesses specific features.
“The basic model of a system used as a tested combination shall consist of one outdoor unit, with one or more compressors, that is matched with between two and five indoor units; for multi-split systems, each of these indoor units shall be designed for individual operation.” The definition goes on to delineate the requirements for the indoor units as well.
Roxanne Scott, national product manager for Heat Controller Inc., Jackson, Mich., pointed out that multiple configurations are difficult to test and present many challenges and complexities. “However, all of these complexities were reviewed by the DOE and captured under the new test standards.”
The second challenge raised was “quantifying the testing and rating methodology for ducted and non-ducted indoor units when combined to a multi-split condensing unit.” In addressing this challenge, the DOE requires that each unit be tested and rated with a combination of ducted indoor units where applicable, and non-ducted units as well.
“The systems are rated in three combinations, one with ducted indoor units, one with non-ducted indoor units, and one with mixed indoor units,” explained Gary Nettinger, vice president of technical solutions for Sanyo Commercial Solutions, Kennesaw, Ga. “Basically there are two sets of tests: ducted and non-ducted. The mixed rating is simply the average values from these.”
The third major challenge that Smith pointed out was “addressing the best way of determining SEER/HSPF levels via the variable-speed compressors.” According to Smith, it was resolved by developing explicit testing conditions and compressor speed requirements for variable compressor equipment.
“The DOE defined mandatory tests for cooling and heating operation, with the ultimate result being the SEER and HSPF efficiency levels of each system (condensing units),” he said.
According to Nettinger, within the new testing, the variable-speed compressor is operated at three different speeds in cooling and three different speeds during the heating test as well.
“One test is at minimum compressor speed, one at a maximum speed (rated), and the third test is at a speed within the range of 1/4 to 3/4 of the min/max range,” he explained. “This intermediate speed should represent the system’s peak efficiency value. Using the AHRI 210/240 provides the guidance for these tests and the formula to calculate the resulting SEER and HSPF.”
EQUAL PLAYING FIELDOne of the primary benefits to the HVACR industry of a new procedure is less ambiguity in regard to energy efficiency by which variable-speed multi-splits are certified, said Scott. According to Smith, it allows this equipment to be compared transparently to other more established equipment.
“The gray area of the ductless portion of the industry is somewhat removed,” he said. “The manufacturers can actively promote the very good efficiencies their systems deliver, and consumers can have the confidence that the system they are purchasing is certified and the efficiency levels they are paying for will be delivered.”
Nettinger acknowledged that the industry is beginning to understand the “unique operating characteristics of variable-speed multi split products.
“Manufacturers are now awarded the opportunity to have their system’s performance and efficiency more adequately represented,” he pointed out.
“For the manufacturer, it is now clear which standards variable-speed multi-splits must meet for certification,” said Scott. “For the consumer, the consistency of the certification standards and testing practices will allow them to compare apples to apples.”