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Fan Energy Index (FEI) & Fan Electrical Power (FEP)

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Fan Efficiency Measurement using new FEI, FEP equations

Bathroom ceiling vent fan, heater, light combination (C) Daniel FriedmanIn September 2017 the Fan Regulation Committee of the Air Movement Control Association (AMCA) described recent agreement on two new fan efficiency measurements, the Fan Energy Index (FEI) and the Fan Electrical Power (FEP) that can be used to describe the efficiency of air movement equipment, i.e. fans.

The intent of FEI and FEP is to permit consistent and meaningful development of rules for fan design, use, and selection. FEI, when accepted by the U.S. Department of Energy (DOE) will replace the current fan energy metrics used in model energy codes and standards used in the United States.

The effect of a standard of this type is that there will not be a single pass-fail number for a fan; rather the performance of a specific fan model will be understood to vary by where and how the fan is used.

[Click to enlarge any image]

Why A New Fan Efficiency Standard?

The AMCA committee, writing in the fall issue of AMCA's publication, AMCA in motion, explain that in actual use the energy-efficiency of fans varies significantly depending on how and where a fan is used.

For example the leakiness of the building envelope for a specific structure can significantly affect how a fan performs in that environment - more-so than would be affected the efficiency of some other appliances such as a light bulb that doesn't care much where it is providing illumination.

The committee explains that the very same fan might work very efficiently in some locations and very inefficiently in others.

The intent of the new FEI FEP measurements is to permit the most efficient fan model and type is selected for its specific application by looking at just the FEI rating on the fan label.

Instead of specifying a minimum peak efficiency level for each of the various fan types, FEI establishes a baseline efficiency and resulting baseline power that varies with both airflow and pressure, universally applied to all fan categories. (AMCA 2017)

Definition of Fan Energy Index FEI by Equations

  1. FEI = Fan Efficiency / Baseline Fan Efficiency
  2. FEI = Baseline Fan Electrical Input Power / Electrical Input Power

The second equation is preferred as the object of fan standards is to reduce wasted energy.

Definition of Fan Electrical Power FEP used to derive FEI

FEP is obtained by

Direct measurement of the fan's electrical power input during rating tests

or

Measuring the fan shaft power and incorporating default values for motors and drives. The default values are defined in AMCA Standard 207 (in process of approval as of Fall 2017)

The FEP rating (in kilowatts or kw) for a specific fan is compared against a baseline or "standard" FEPstd to permit deriving FEI

  1. FEI = FEPstd / FEP rating

The AMCA committee anticipates that regulatory and energy standards for fans will express a requirement such as FEI >= 1.0 at design point

Why FEP & FEI Work

The AMCA committee explain that for each type of fan, FEI expresses a baseline efficiency and a resulting baseline power that will vary as both air flow and power vary.

For a fan to be compliant with a standard it simply has to deliver sufficient air flow at a specified or sufficient pressure, at a specific FEI ratio (for example 1.0) as shown in equation 3 above.

Whenever the FEI ration shown in equation 3 is greater than 1.0 the amount of energy saved (over the baseline) will be FEI - 1.0 expressed in percent.

A fan that is rated at FEI 1.1 provides the following energy savings over the baseline requirement:

(FEI 1.1) - (FEI 1.0) = 0.1 Energy Savings i.e. 10% saved over the baseline standard.

The purpose of this rating method is to permit FEI to define a compliant range of operation (for varying air pressure, air flow, and energy used to power the fan) instead of a single number. This approach works as well for multiple speed or variable speed fans too, creating a compliant zone of operation that will be described by the fan manufacturer for each fan model.

Where would fans with an FEI of less than 1.0 be permitted? The committee anticipates that there will be allowable exceptions (that is FEIs <1) for fan systems that use variable air volume (VAV systems) used for material handling or in emergency applications.

The committee explain that code authorities and the U.S. Department of Energy may set minimum FEIs for fan applications (or maximum fan power), but the fan manufacturers (and users) can meet these requirements with their choice of specific fan properties: fan motor, transmission, speed control or other features.

Resources & References for FEI & FEP & Fan Efficiency Standards


Continue reading at BATHROOM FAN ENERGY COST or select a topic from the More Reading links or topic ARTICLE INDEX shown below.

Or see AIR FLOW MEASUREMENT CFM

Or see BACKDRAFTING HEATING EQUIPMENT

Or see BATHROOM VENTILATION CODES SPECS

Or see BLOWER FAN OPERATION & TESTING

Or see FAN NOISES in BUILDINGS

Or see KITCHEN VENTILATION DESIGN

Or see ROOF VENTILATION SPECIFICATIONS - home

Or see SEER RATINGS & OTHER DEFINITIONS

Or see VENTILATION in BUILDINGS - home

Suggested citation for this web page

FAN ENERGY INDEX FEI at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

INDEX to RELATED ARTICLES: ARTICLE INDEX to ARTICLE INDEX to BUILDING VENTILATION

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