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Twin coils heat exchangers
Certification manual
Certification Manual
Technical Certification Rules

Scope of the Programme

The programme scope covers the heat recovery exchangers with intermediate heat transfer medium corresponding to the category IIa (“without phase change”) of the EN 308:1997 standard, that is Run Around Coils systems.

The present programme does not cover other types of air to air heat exchangers like Air to Air Plate Heat Exchangers (AAHE) or Air to Air Regenerative Heat Exchangers (AARE) for which dedicated Eurovent Certified Performance programmes exist.


For definitions regarding the certification scheme refer to Certification Manual.

Heat recovery system with intermediary heat transfer medium

Heat exchanger or combination of heat exchangers that transfer heat between exhaust and supply air flows by the means of an intermediary heat transfer medium and depending on the differential of temperatures.

Run around coil system

A run around coil system, simply called “system” in the programme, consists of a coil in the extract air and a coil in the supply air; with a pipe system in between to transfer the recovered energy from one air stream to another.

The coil located in the extract-exhaust air stream is called “exhaust coil” and the coil located in the outdoor-supply air stream is called “supply coil” in the HRS-COIL Certification programme.

Range for Run around coils

Coils dedicated to heat recovery and having the following identical features:

  • designation
  • tube outside diameter
  • tube arrangement :
    • pitch height : tube spacing (i.e perpendicular to the air flow)
    • pitch depth : row spacing (i.e in direction of the air flow)
    • tube alignment (in-line or staggered)
  • minimum and maximum number of rows
  • minimum and maximum number of tubes per row
  • minimum and maximum finned length


A bank of tubes that are located in a plane at right angle to the direction of the air flow.

Basic Model Group

Within a range, models which are essentially the same or comparable in terms of basic components and/or configurations combinations are gathered into basic model groups (BMG).

The following variations distinguish one BMG from another:

  • tube type (plain or inner-grooved)
  • tube material category
    • standard : Copper (Cu);
    • special : any other material;
  • fin type (flat, corrugated, louvered, wavy)
  • fin material for a given fin type
  • reference fin spacing (RFS) for a given fin thickness

A reference fin spacing (RFS) is considered representative of a range of fin spacings from 0.7 to 1.3 times its value.

Example: The applicant range covers fin spacings (FS) from 2.0 to 8 mm in the following steps: 2.0, 2.5, 3.0, 4.0, 5.0, 6.0, 7.0 and 8.0 mm. Considering the aforementioned rule there are three (3) reference fin spacings (RFS):

  • 2.5 covers the range [1.8; 3.3] so it is considered representative of 2.0, 2.5, 3.0
  • 5.0 covers the range [3.5; 6.5] so it is considered representative of 4.0, 5.0, 6.0
  • 8.0 covers the range [5.6; 10.4] so it is considered representative of 7.0 and 8.0

Dry heat recovery efficiency

The temperatures at the coils limits are the following:

t11 : exhaust air inlet (“extract air”) dry temperature (°C)

t12 : exhaust air outlet (“exhaust air”) dry temperature (°C)

t21 : supply air inlet (“outdoor air”) dry temperature (°C)

t22 : supply air outlet (“supply air”) dry temperature (°C)

The dry heat recovery efficiency is a temperature ratio defined on the supply-air side for equal air flows and winter conditions (no condensation on the exhaust air side):

HS efficiency

Certified performance items and associated tolerances

When tested in the laboratory the obtained performance data shall not differ from the recalculated values (“test-check”) by more than the following tolerance values:

Dry heat recovery efficiency:  -3 percentage points (abs. deviation)

Air side pressure drop :  Maximum [+10%;+15 Pa]

Fluid side pressure drop :  Maximum [+10 % ; +2 kPa]

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