Regulations, standards and guidelines have over time defined various indicators of heat recovery, some of which are also formulated as minimum requirements.

Hoval has many years of experience in the field of energy recovery. But that doesn’t mean it can rest on its laurels. The company’s mission is to keep developing superior solutions to meet today’s challenges – and tomorrow’s.

A great advantage of plate heat exchangers is the separation of the supply and extract air flows. This means impurities, odours as well as moisture cannot be transferred.

Energy recovery always acts like a temperature rectifier between the two air streams. Output control is therefore not necessary as long as the extract air temperature corresponds to the setpoint/room temperature.

The internal leakage of a rotor results from the seal leakage and the carryover. While the leakage depends on the seal quality and the pressure difference, the carryover is due to functional reasons.

There are different pressures on the supply and extract side of a ventilation system – depending on the installed components and the arrangement of the fans.

If humid air is cooled down, the relative humidity rises until condensate is formed. If the outside air is so cold that the extract air is cooled below the freezing point of the condensate, it can freeze and block the heat exchanger on the extract air side partially - or in extreme cases even completely.

The transfer of partial mass flows from one air flow to the other is referred to as (internal) leakage. It is caused by leaks as a result of a pressure difference (seal leakage) or is function-related, such as the co-rotation of a rotor. This is pointed out in the guideline VDI 3803 sheet 5. At the same time, key figures are defined to indicate the size and type of leakage.

The European Regulation EU 1253-2014 limits the energy consumption of ventilation systems with a capacity greater than 250 m³/h for non-residential premises (NRVS). The reference configuration of the bidirectional ventilation system BVS is a casing with two fans, a heat recovery system HRS and one supply air and one exhaust air filter each.

Since the first energy crisis in 1973, heat recovery in HVAC systems has become the benchmark in the industry – even though there was previously no obligation to use it and no mention of minimum thermal efficiency. With the implementation of the Ecodesign Directive...