ISO 12759-3:2019

Overview

ISO 12759-3:2019 - Fans - Efficiency classification for fans - Part 3: Fans without drives at maximum operating speed establishes a uniform system to classify the energy efficiency of fans that have no attached drive (impeller-only or “fan without drives”) and a nominal shaft power ≥ 0.125 kW. The standard defines how to determine a fan’s optimum (peak) efficiency at its maximum permissible rotational speed and assigns a Fan Efficiency Grade (FEG) (for example FEG85, FEG80, FEG71) based on the best-efficiency point. It is intended for manufacturers, test laboratories and regulators and can be used by legislators to set energy-saving targets.

Key topics and requirements

• Scope and applicability: Applies to fans only (not motors, belts, VFDs or broader systems); nominal shaft power 0.125 kW and above.
• Efficiency metric: Efficiency is taken at the fan’s best-efficiency point (optimum efficiency) at maximum operating speed.
• FEG classification: Defines fixed efficiency grades (FEG50 through FEG90 ranges) tied to fan impeller diameter; a fan’s grade is determined by comparing its peak efficiency to grade boundary curves. Annex A provides the boundary Formula (A.1) and constants plus tabulated grade limits (Table A.2).
• Testing and configurations: Manufacturers shall declare the test configuration used. Four standardized configurations (Categories A–D from ISO 5801:2017) are referenced for determining the operating point.
• Normative references and tolerances: Relies on ISO 5801 (performance testing), ISO 13348 (tolerances and data presentation) and ISO 13349 (vocabulary). Specified measurement tolerances and conversion methods apply.
• Labeling rules: A fan is assigned an FEG when its optimum efficiency falls between the upper and lower limits for its size; no FEG is assigned below FEG50.

Applications and users

• Manufacturers: design verification, product certification, marketing and performance claims.
• Test laboratories: standardized test methods and reporting for consistent FEG assignment.
• Regulators and legislators: defining minimum efficiency requirements and energy-saving targets for fan products.
• Specifiers, purchasers and energy auditors: comparing fan options for HVAC, ventilation, process engineering, drying, pneumatic conveying and agricultural fans.

Related standards

• ISO 5801:2017 - Fans - Performance testing using standardized airways
• ISO 13348:2007 - Industrial fans - Tolerances, methods of conversion and technical data presentation
• ISO 13349 - Fans - Vocabulary and definitions

Keywords: ISO 12759-3:2019, fan efficiency classification, fans without drives, Fan Efficiency Grade (FEG), best efficiency point, ISO 5801, energy efficiency for fans.