# Commission Regulation (EU) No 327/2011 of 30 March 2011 implementing Directive 2009/125/EC of the European Parliament and of the Council with regard to ecodesign requirements for fans driven by motors with an electric input power between 125 W and 500 kW (Text with EEA relevance), Division 3.1: Where the fan is supplied as a ‘final assembly’, measure the gas power and the electric input power of the fan at its optimum energy efficiency point:

Extent: E+W+S+N.I.

(a) where the fan does not include a variable speed drive, calculate the overall efficiency using the following equation:
ηe = Pu(s) / Pe
where:
ηe is the overall efficiency;
Pu(s) is the fan gas power, determined according to point 3.3, of the fan when it is operating at its optimal energy efficiency point;
Pe is the power measured at the mains input terminals to the motor of the fan when the fan is operating at its optimal energy efficiency point;
(b) where the fan includes a variable speed drive, calculate the overall efficiency using the following equation:
ηe = (Pu(s) / Ped) · Cc
where:
ηe is the overall efficiency;
Pu(s) is the fan gas power, determined according to point 3.3, of the fan when it is operating at its optimal energy efficiency point;
Ped is the power measured at the mains input terminals to the variable speed drive of the fan when the fan is operating at its optimal energy efficiency point;
Cc is a part load compensation factor as follows:
for a motor with a variable speed drive and Ped ≥ 5 kW, then Cc = 1,04,
for a motor with a variable speed drive and Ped < 5 kW, then Cc = – 0,03 ln(Ped) + 1,088.

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Source: https://www.legislation.gov.uk/eur/2011/327/annex/II/division/3/division/3.1 (the official version)
Page: https://openlegislation.uk/eu-regulation-2011-327/annex-II/division-3/division-3.1
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.