Hoval presents new sealing with minimum leakage for rotary heat exchangers

Directives and standards are increasingly focusing on leakage in rotary heat exchangers. Modern rotary heat exchangers are often only equipped with simple brush seals or inflexible fixed sealings, which cannot reliably prevent leakage.

Hoval has developed and patented the answer to this problem; a sealing system based on a constant-force spring which presses the seals permanently and with consistent pressure against the casing.

Hoval rotary heat exchangers equipped with this system therefore have extremely low leakage rates. This is significant not only from the point of view of hygiene, but also when it comes to energy technology, because the aim of an air conditioning system is to bring fresh air into a building. Leakage means that recirculating air is supplied instead of fresh air. While just as much electrical power is required to convey recirculating air as fresh air, recirculating air has no effective benefit.

Fans are the largest consumers of electrical energy in modern air conditioning units. That is why high-quality rotor sealing is extremely important for efficient operation of the units. VDI Directive 3803 Sheet 5, currently still in the draft stage, addresses this issue. It stipulates that the size of air handling units must be increased by the amount of their leakage at the rotary heat exchanger. This means that unit manufacturers equipping their systems with the especially leaktight rotary heat exchangers from Hoval can size their units smaller – this saves costs and energy.

The selection program Hoval CARS automatically allows for the leakage of rotary heat exchangers depending on type and differential pressure in the design calculation. The CARS program is certified by Eurovent and TÜV (German technical inspection agency) and is available for free download on the Internet (wrg.hoval.com).

Patented sealing system from Hoval: Constant-force springs press the seals permanently and with consistent pressure against the casing.

The outstanding leak-tightness of Hoval rotary heat exchangers means that air handling units can be sized smaller.

Media contacts:


Alina Ivanescu


Tel. +423 399 2665

Fax +423 399 2363

Hoval Aktiengesellschaft

Austrasse 70

9490 Vaduz

Tel. +423 399 2400



Roland Boss


Tel. +41 (44) 925 61 11

Fax +41 (44) 923 62 56

Hoval AG

General Wille-Str. 201

8706 Feldmeilen


Heike Mahler


Tel. +49 (0) 89 922097 128

Fax + 49 (0) 89 922097 840

Hoval GmbH

Humboldtstrasse 30

85609 Aschheim

Tel. +49 (0) 89 922097 0



Thomas Bacik


Mobil +43 (0)664 600 555 911

Fax +43 (0)50 365 99 5911

Hoval Gesellschaft mbH

Hovalstrasse 11

4614 Marchtrenk

Tel. +43 (0)50 365 0



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