This document establishes a system for the classification of fan efficiency for all fan types driven by motors of nominal rating 0,125 kW and above. It applies to driven fans only, but not to the system (finished original equipment manufacturer's product, for example box fans and roof fans or ventilation system) in which they might be installed. This document describes a number of different procedures to classify the efficiency of a fan or to apply a minimum efficiency limit (MEL). Those procedures are described in:

— ISO 12759-3;

— this document (ISO 12759-4);

— ISO 12759-5;

— ISO 12759-6.

There is no method described to compare these classifications and MEL's.