Fan Energy Index (FEI) is a metric that encourages mechanical designers to make fan selections closer to a fan’s peak efficiency. The higher the FEI, the less power is consumed at a given duty point (airflow and pressure). FEI is a ratio of the input power of a reference fan and the actual fan at the same duty point.
The requirement applies to fans or fan arrays that exceed a combined motor nameplate horsepower greater than 1.00 hp or a combined fan nameplate electrical input power greater than 0.89 kW.
There are many exceptions to this requirement, primarily intended to exclude fans whose efficiency is regulated by another metric. Exception 1 to Section 120.10(a) covers this category. As Exception 1 states, any embedded fans in equipment listed under Section 110.2|topic=SECTION 110.2 – MANDATORY REQUIREMENTS FOR SPACE-CONDITIONING EQUIPMENT, Section 110.1 computer room air conditioners (CRACs) as defined in 10 CFR 431, and dehumidifying direct exchange dedicated outdoor air systems (DX-DOASes) do not need to meet the requirements of 120.10. For example, the supply fan of a commercial unitary air conditioner, which is listed in section 110.2|topic=SECTION 110.2 – MANDATORY REQUIREMENTS FOR SPACE-CONDITIONING EQUIPMENT, does not need to meet the requirements of section 120.10.
AMCA 208 defines an embedded fan as “a fan that is set or fixed firmly inside or attached to a surrounding piece of equipment whose purpose exceeds that of a fan or is different than that of a standalone fan. This equipment may have safety or energy efficiency requirements of its own. Examples of embedded fans include supply fans in air handling units, condenser fans in heat rejection equipment, tangential blowers in air curtain units and induced or forced draft combustion blowers in boilers or furnaces.”
Other exceptions include embedded fans and embedded fan arrays with a combined motor nameplate horsepower of 5 hp or less or with a fan system electrical input power of 4.1 kW or less (Exception 2), circulation fans, ceiling fans and air curtains (Exception 3), and fans that are intended to only operate during emergency conditions (Exception 4).
For in-scope fans, the requirement is that fans in multi-zone VAV systems must meet an FEI of 0.95 or greater, and all other fans must meet an FEI of 1.0 or greater. The FEI value shall be provided by the manufacturer. For more information about FEI, including how it is calculated, consult with ANSI/AMCA 208.