# Commission Regulation (EU) No 1253/2014 of 7 July 2014 implementing Directive 2009/125/EC of the European Parliament and of the Council with regard to ecodesign requirements for ventilation units (Text with EEA relevance), Division 1: THERMAL EFFICIENCY OF A NON-RESIDENTIAL HEAT RECOVERY SYSTEM

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

The thermal efficiency of a non-residential heat recovery system is defined as
η t_nrvu = t 2 ″ − t 2 ′ ∕ t 1 ′ − t 2 ′
where:
ηt is the thermal efficiency of the HRS [-];
t2″ is temperature of the supply air leaving the HRS and entering the room [°C];
t2′ is temperature of the outside air [°C];
t1′ is temperature of the exhaust air, leaving the room and entering the HRS [°C].

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Source: https://www.legislation.gov.uk/eur/2014/1253/annex/IX/division/1 (the official version)
Page: https://openlegislation.uk/eu-regulation-2014-1253/annex-IX/division-1
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.