Energy-saving method checks refrigerant level in air co...( WEST LAFAYETTE Ind. - Engineers hav...)

WEST LAFAYETTE, Ind. - Engineers have developed a technique that saves energy and servicing costs by indicating when air conditioners are low on refrigerant, preventing the units from working overtime.

The new "virtual refrigerant charge sensor" is particularly practical for automotive air conditioners, which tend to leak refrigerant more than other types of units, and also for household central air conditioning units, said James Braun, a professor of mechanical engineering.

Maintaining the proper "charge," or amount of refrigerant in a system, saves energy because air conditioners low on refrigerant must operate longer to achieve the same degree of cooling as properly charged units.

"Not only does the energy efficiency go down, but you also reduce the lifetime of the unit because it has to work harder, causing parts to wear out faster," Braun said. "It's also very time consuming and costly to have a technician check the refrigerant and charge it up to specification. To accurately learn how much charge is in the system, you have to remove all of the refrigerant and weigh it, a procedure that requires a vacuum pump and is quite time consuming."

The new alternative works by using sensors to monitor the temperature of refrigerant at various points along the tubing in an air-conditioning unit. The technique is easy to use because the sensors are simply attached to the outside of the tubing, Braun said.

Researchers tested the system on various types of air conditioners running on conventional refrigerants, including R-22 and the more environmentally friendly R-410A, which is replacing R-22 in the latest units. The research has been funded by the California Energy Commission through its Public Interest Energy Research, or PIER, program.

Findings are detailed in a research paper presented June 22 during a meeting of the American Society of Heating, Refrigerating and Air Conditioning Engineers in Louisville, Ky
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