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How can You install heat recovery unit in the ready-built house?

Heat recovery unit HRU-WALL

Investors put a greater and greater emphasis on energy savings in the newly built buildings, striving for minimisation of heat losses. As the insulation of the building partitions increases, entailing the reduction of losses by the exchange of heat with the surroundings, the heat which is necessary for heating the ventilation air has a greater and greater share in the energy balance. The supply of the appropriate amount of fresh air is necessary for the proper functioning of man and prevents the condensed water formation and development of microorganisms and fungi.  

In the classic solutions, the air from the building interior is removed and the fresh ventilation air must be heated to the temperature that guarantees comfort to the persons staying inside the rooms. However, there is a number of systems, allowing the part of the lost heat to be recovered and used for the preheating of the supplied outside air, significantly decreasing the heat demand. Inasmuch as it is relatively easy to implement the ventilation system with heat recovery at the stage of designing and erecting the non-existent building, it is not always possible in the case of the existing buildings. A solution which is effective, simple in assembly and operation includes recuperators mounted inside the walls, applicable both in the upgraded and newly built residential and utility buildings. 


The basic elements of the HRU-WALL-150-60 single-tube recuperator mounted inside the wall include the ceramic heat exchanger, the reversible fan and the air filter. The device operates in two stages alternate every 70 seconds. In the first one, the air is blown out, and flowing through the honeycomb exchanger, it gives off up to 82% of the heat energy and humidity to it. When the heat exchanger is heated, the device switches into the supply mode, and the accumulated energy and humidity are drawn in by the fresh air supplied into the building. Cycles change automatically, which ensures the uninterrupted air change and filtration.  The most effective use takes place when a pair of units in the neighbouring premises connected with each other by means of the HRU-WALL-CONTR-I regulator is used. This allows the alternate operation, when one of the recuperators operates in the exhaust mode, the air in the second one is supplied into the building ensuring better air circulation. 

Controller for heat recovery unit

Illustration 1

The set of two recuperators supplies even 120 m3 of fresh air per hour; such a quantity allows the comfortable and proper functioning of 4 persons staying in the ventilated premises. The obtained air volume also ensures the effective removal of humidity and ventilation of the bathroom and kitchen, even four mating units mounted inside the walls will be sufficient to ventilate a house completely and in a fully controlled manner. Because of using an energy-saving drive engine, and a fan with a special construction, placed in the single-tube housing, the consumption of electricity is amazingly low - the average cost of using two devices is less than PLN 30 per year. At the same time, the savings which result from the ventilation heat recovery allow the return of the investment cost within 3 to 5 years. Theoretically, the bills for heating may be smaller by even 90%, however as no building is ideally leak-tight, the real savings which can be achieved amount to about 50-60%. 

Control & operating modes

The heat recovery unit is intended for continuous operation is equipped with a controller which ensures the uninterrupted operation of the fan in three-speed ranges, depending on the use and volume of the premises. Furthermore, operation in the “Boost” mode is ensured, which allows the temporary increase in the volume of the changed air. The mode may be activated manually or by using the sensors that monitor the conditions outside the premises. Owing to the By-Pass function - if the temperature differences are negligible or when the temperature of the air outside is higher than inside the premises, it is possible to transmit the air with the omission of the heat exchanger. In such a case recuperators mounted inside the walls operate like an ordinary supply and exhaust air handling unit without heat recovery. 

Comfort of use  

The materials used in the device allow its failure-free operation within a broad temperature range, from -20 to even 50°C, proving their value perfectly in our climate. On the other hand, the fan construction allows quiet and comfortable use. The sound level is hardly 15 dB,at the capacity of 20m3/h,  21dB at 40 m3/h, and 29 dB at the nominal capacity of 60 m3/h(3) . The unit may be installed in the premises of any destination, without the negative impact on the persons staying inside. 

The drip cap applied provides protection against rain and gives an interesting and aesthetic appearance to the external grille. The device was tested at the TÜV Rheinland laboratory in accordance with the ISO 5801 standards, which guarantees the reliability of the presented data regarding the energy consumption, efficiency and safety of use. The fan has been designed and tested in accordance with the European low voltage directive and the EN60335-2-80 standard, in order to adapt the unit to the safe operation at home.  Due to the compact, single-tube construction, the assembly in the existing buildings is really simple and does not require the performance of extensive construction work. There is no need to interfere with the construction of the building and run the ventilation ducts, the work is limited only to the performance of appropriate openings in the wall.