ISO 12759-4:2019

Overview

ISO 12759-4:2019 - Fans: Efficiency classification for fans - Part 4: Driven fans at maximum operating speed establishes a system to classify the efficiency of driven fans (impellers fitted to or connected to motors) driven by motors of nominal rating 0.125 kW and above. It applies to the fan itself (not the finished system or OEM product) and defines procedures for efficiency classification and the application of minimum efficiency limits (MELs) for fans operating at their maximum operating speed.

Key topics and technical requirements

• Scope and applicability: Applies only to driven fans (with or without variable speed drives) and excludes whole assemblies or ventilation systems.
• Efficiency definitions: Covers a range of efficiencies and performance metrics including:
  • Fan air power and fan static air power
  • Fan impeller efficiency (ηr), fan shaft efficiency (ηa)
  • Overall efficiency without VSD (ηe) and with VSD (ηed)
  • Static overall efficiencies (ηes and ηesd) and optimum efficiency (ηopt)
• Installation categories: Defines installation categories A–D (free/ducted inlet/outlet combinations) that affect measured performance and efficiency classification.
• Classification procedures and grades: Specifies fan efficiency grades for different fan types (axial, centrifugal - forward/backward bladed, mixed flow, cross-flow) - see Clauses 6.3–6.5 for detailed grade assignments.
• Test and reference standards: Normative references include ISO 5801:2017 (performance testing using standardized airways) and ISO 13348:2007 (tolerances and data presentation).
• Annexes: Provide worked examples, compensation factors, guidance on performance variation across installation categories, and selection for best efficiency (Annexes A–E).

Practical applications and who uses it

ISO 12759-4:2019 is used by:

• Fan manufacturers - to classify and declare fan efficiency at maximum speed and to design to meet MELs.
• Specifiers and OEMs - when selecting driven fans for equipment (box fans, roof fans) and ensuring components meet efficiency requirements.
• Regulators and policy makers - to define energy-efficiency requirements and set minimum efficiency limits for driven fan products.
• Test laboratories and certifiers - to perform standardized measurements (per ISO 5801) and assign efficiency grades.
• Energy auditors and system designers - to compare fan options, estimate energy consumption, and optimize selections for energy savings.

Practical outcomes include improved fan selection, compliance with emerging MELs, reduced energy use (fans account for a large share of industrial/HVAC electricity), and consistent international labeling and procurement.

Related standards

• ISO 12759 series (Parts 1–6) - companion documents defining scope, methods, and other operating conditions.
• ISO 5801:2017 - standardized fan performance testing.
• ISO 13348:2007 - tolerances and presentation of fan technical data.

Keywords: ISO 12759-4:2019, fans efficiency classification, driven fans, maximum operating speed, minimum efficiency limit (MEL), fan efficiency grades, installation categories, fan performance.