The nine-week study, funded by the California Energy Commission, will look at energy savings realized through the use of an Enhanced Fan Delay - a retrofit device HVAC contractors can apply to residential air conditioners to improve cooling performance in hot-dry climates.

“After a system’s compressor shuts down in hot-dry environments such as the Western U.S., water that has condensed on the evaporator coil can be re-evaporated into the conditioned space to boost the sensible efficiency of the unit,” said Adrian Hairrell, an engineer with Proctor Engineering Group (PEG), the San Rafael, CA-based engineering consulting firm developing the devices.

“The purpose of this study is to compare the energy use of a standard system to that of the same system with the Enhanced Fan Delay control added. Our goal for the project is to realize at least 7% energy use savings in each California climate zone we monitor.”

The monitoring period for each participating home will run for approximately nine weeks beginning in May 2010. All participating homes are located within the San Joaquin Valley region, where blazing summertime temperatures - reaching 115° F - lead to heavy air conditioning use among residents.

The Onset data loggers, which are compact, battery-powered devices, will be installed on the air conditioning units to measure supply and return air temperatures, fan and compressor runtime patterns, and compressor amperage. The recorded data will be offloaded onto a PC using accompanying HOBOware graphing and analysis software, and then exported into a spreadsheet program for detailed analysis.

“In the past, we’ve used data logging devices that could take up to eight hours to install at each site, which can be very imposing on the homeowner,” said Hairrell. “One of the benefits of the Onset loggers is that they can be installed very quickly - minutes vs. hours - so the homeowner doesn’t have to spend a lot of time waiting around.”

The results of the study are expected to be published in a report in early 2011.


Onset is the world’s leading supplier of data loggers. The company’s HOBO data logger and weather station products are used around the world in a broad range of applications, including building energy performance monitoring, water resources management, and ecological and agricultural research.  Based on Cape Cod, Massachusetts, Onset has sold more than 1.5 million data loggers since the company’s founding in 1981. Visit Onset online at


Proctor Engineering Group (PEG) specializes in the design and evaluation of energy efficiency programs for electric and gas utility companies nationwide. With a combined total of more than 80 years’ experience in industry consulting and research, building diagnostics, HVAC efficiency, program evaluation, and quality assurance and training, the company can design and implement efficiency programs that maximize energy savings and reduce peak demand. Visit Proctor Engineering Group online at

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