Construction products detail

Flue gas heat exchangers

Flue gas heat exchangers transfer the thermal energy from the heating appliance flue gas to the heating water. This increases the efficiency of the heating system.

Regulatory framework

In this work area, DIBt grants:

  • national technical approvals (abZ) for flue gas heat exchangers that are not covered by the applicable harmonised standards or a European Technical Assessment;
  • general construction technique permits (aBG) for the design and execution of the corresponding applications.

National technical approvals and general construction technique permits can be granted together in a single decision ('combined decision').

European Technical Assessments (ETAs) can also be issued for flue gas heat exchangers that are not (fully) covered by a harmonised standard. For construction products covered by an ETA, a general construction technique permit for the application may be pertinent.

 The technical rules to be observed for the application of flue gas heat exchangers include:

  • DIN EN 12828 – Heating systems in buildings – Design for water-based heating systems
  • DIN EN 13384-1 – Chimneys – Thermal and fluid dynamic calculation methods – Part 1: Chimneys serving one heating combustion
  • DIN EN 13384-2 – Chimneys – Thermal and fluid dynamic calculation methods – Part 2: Chimneys serving more than one heating appliance

Please also note the relevant provisions of the federal states following MVV TB, Section B

For the assessment of the above-mentioned construction products and techniques within the framework of the national procedures, DIBt prepares application-specific test plans. DIBt approval principles and preliminary test programmes form the basis for this.

The approval principles and preliminary test programmes are no conclusive technical rules, but rather compilations helping to speed up the procedure. They are not published, but are made available to the applicants during the approval or permit procedure.

The following preliminary test programme has been prepared up to now:

Preliminary test programme for flue gas heat exchangers for completing or retrofitting of firing systems with non-room-sealed heating appliances (Vorläufiges Prüfprogramm für Abgaswärmeübertrager zur Komplettierung von /oder zum nachträglichen Einbau in Feuerungsanlagen mit raumluftabhängigen Feuerstätten)

National procedure

A national technical approval (abZ) and/or oder general construction technique permit (aBG) is granted upon application (see Model Building Code (MBO), Sections 16a(2) and18(2) and (4)). This also applies to amendments and supplements to, or renewals of existing approvals and/or construction technique permits.

No formal requirements apply. The following information is needed: name and address of the applicant, description of the product and/or construction technique and its field of use or application, type of decision required (new decision, amendment or supplement to, or renewal of, an existing decision).

Please feel free to use the template below.

European Technical Assessment (ETA)

To start the ETA procedure, please submit the form below. We will then check if the prerequisites for issuing an ETA are met, i.e., in particular, if the product is not fully covered by an existing harmonised standard. If the prerequisites are met, we will check whether a European Assessment Document (EAD) covering the requested assessment scope already exists or still needs to be developed. If an EAD needs to be developed or amended, a complete technical file needs to be established before the procedure can begin.


new decision
valid until
Subject concerned Applicant Decision no. Validity
from / to
Abgaswärmeübertrager "ÖKO-Carbonizer" EISN GmbH Am Wall 9 89434 Blindheim Z-43.31-200 Z: 10.10.2023
G: 29.05.2024
Abgaswärmeübertrager mit den Bezeichnungen "GPH AK 28", "GPH AK 50" und "GPH AK 75" sowie "GPH HP 28", "GPH HP 50" und "GPH HP 75" ATEC GmbH & Co. KG Abgastechnologie Liliencronstr. 55 21629 Neu Wulmstorf Z-43.31-222 Z: 14.05.2019
G: 18.06.2024
Abgaswärmeübertrager mit den Bezeichnungen "AWT - S1, AWT - S2" Ulrich Bachmann Innovative Klima- & Lufttechnik Hauptstraße 5 08237 Steinberg/OT Rothenkirchen Z-43.31-261 Z: 09.11.2021
G: 09.11.2026
Abgaswärmeübertrager mit der Bezeichnung "AWT - S3" Ulrich Bachmann Innovative Klima- & Lufttechnik Hauptstraße 5 08237 Steinberg/OT Rothenkirchen Z-43.31-262 Z: 10.11.2021
G: 10.11.2026
Abgaswärmeübertrager mit den Bezeichnungen "AWT" und "AWT-BP" Karl Schräder Nachf. Hemsack 11-13 59174 Kamen Z-43.31-300 Z: 27.11.2017
V: 28.11.2022
G: 28.11.2027
Abgaswärmeübertrager "TurbuFlex-System" Dipl.-Ing. Klaus Schmitt Konstruktion Abgaswärmetauschersysteme Siegenstraße 132a 44359 Dortmund Z-43.31-337 Z: 02.12.2022
G: 07.12.2027
Abgaswärmeübertrager mit den Bezeichnungen "HWAR R" und "HWAR L" zur Rückgewinnung der trockenen Wärme aus den Heizgasen von Feuerstätten des Herstellers Camina & Schmid Feuerdesign und Technik Camina & Schmid Feuerdesign und Technik GmbH & Co. KG Gewerbepark 18 49143 Bissendorf Z-43.31-390 Z: 09.03.2021
G: 09.03.2026
Abgaswärmeübertrager mit den Bezeichnungen "Thermojekt SK", "Thermojekt R" und "Thermojekt RB" Kutzner + Weber GmbH Frauenstraße 32 82216 Maisach Z-43.31-458 Z: 01.08.2019
G: 01.08.2024
Abgaswärmeübertrager mit der Bezeichnung "TurbuFlexS" K. Schräder Nachf. Inh. K.-H. Schräder Hemsack 11-13 59174 Kamen Z-43.31-462 Z: 13.08.2019
G: 13.08.2024
Abgaswärmeübertrager mit den Bezeichnungen "ETA WT BG 1" bis "ETA WT BG4" ETA Heiztechnik GmbH Gewerbepark 1 4716 HOFKIRCHEN ÖSTERREICH Z-43.31-465 Z: 01.11.2019
G: 01.11.2024
Abgaswärmeübertrager mit den Bezeichnungen "TurbuFlexS-600 Condens" und "TurbuFlexS-1200 Condens" für den Kondensationsbetrieb Karl Schräder Nachf. Hemsack 11-13 59174 Kamen Z-43.31-477 Z: 09.11.2021
G: 09.11.2026