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BPA has assessed advanced control retrofits for rooftop HVAC units in small commercial buildings and retail stores. To maximize electrical energy savings, a full package of ARC features was field-tested, including supply fan control with a variable-frequency drive or fan cycling control, upgraded economizer controls, and remote web control and monitoring.  Additional desirable features include demand-controlled ventilation, other control options, and variable compressor operation.  Average energy savings were found to be between 25 and 40 percent of the rooftop unit electricity use.  While several field-test applications showed higher savings, these were not considered normal applications.  The biggest factor found to affect electricity use was the hours of operation.
In addition, a “Lite” package of ARC features was also field-tested, including supply fan control with a variable-frequency drive, and controls to ensure adequate ventilation at low speeds, as required by Mechanical codes.  Expected energy savings are between 15 and 30 percent of the rooftop unit electricity use.

Current Stage: Emerging Technology Assessment
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