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The U.S. Department of Energy (USDOE) efficiency metric for large diameter ceiling fans (LDCF) was replaced by a new metric in 2021. LDCF are fans with a blade span (diameter) of 2.1 m (7.0-ft) and have been regulated In the United States since 2017 (test procedure) and 2019 (energy standard).
In a highly unusual development, a U.S. law was passed in 2020 to change the regulatory metric because the USDOE metric unintentionally capped the performance of LDCFs that had a high airflow utility relative to its blade span – i.e., larger-diameter fans can barely comply with the USDOE requirement even though they are highly efficient for their utility, and future evolution of these products was unfairly limited. The law led to a change in the U.S. Code of Federal Regulations in 2021 that put the CFEI metric into effect.
In legal documents, the USDOE metric was expressed only in inch-pound units of cubic-feet-per-minute (cfm) per watt (DOE cfm//W), averaged over time-weighted five test speeds, and with an integrated idle-fan standby-power measurement (the metric equivalent that is used in the Presentation Without Paper is cubic meters per second m3/s). The cfm/W metric was replaced by Ceiling Fan Energy Index (CFEI), which is not time weighted, is calculated at two test speeds, and does not integrate an idle-fan standby-power measurement.
The CFEI metric has more stability over the range of fan operating speeds and provides a more accurate depiction of fan performance at higher airflows. CFEI also is less prone to abuse by bad actors that could meet efficiency requirements by simply slowing down an inefficient fan. Because the standby power measurement was eliminated, CFEI offers a more accurate representation of fan efficiency across its operating range.
CFEI is a unitless metric calculated from performance-rating tests conducted in accordance with the USDOE test procedure, which references ANSI/AMCA Standard 230-15, “Laboratory Methods of Testing Air Circulating Fans for Rating and Certification.” There is no equivalent ISO standard to AMCA 230. CFEI is based on the Fan Energy Index (FEI) metric that was developed for commercial and industrial fans. FEI is a wire-to-air metric being used in the United States for energy codes used for buildings, and in state and federal fan regulations. FEI is being integrated into the ISO standards community as ISO 12759-6.
This presentation describes the CFEI metric, how it is calculated and applied. It also describes the ANSI/AMCA 230 test standard and updates the audience on revisions to the standard that are being considered during its current review/update cycle.