Manufacturers of heat recovery units prefer not to talk much about preheating. Well, it is understandable because the average consumption of preheating is 1.5 kW per hour. The fact is that they simply cannot work without it in freezing weather. The condensate which forms in the heat exchanger starts to freeze and the unit becomes non-functional.

In winter, the waste air flowing through the heat exchanger transfers its heat to the fresh air and cools itself. During severe cold, the exhaust air cools down to the point where condensate forms in the heat exchanger (dew point occurs).

As long as the fresh air temperature is above zero, the condensate simply flows out of the ventilation unit. However, as soon as the fresh air is below zero, icing forms instead of condensate. The frozen condensate gradually clogs the heat exchanger and in prolonged operation could tear it apart.

An electric heating coil is the most common frost protection. It is 100% functional and easy to operate. The main disadvantage is the electricity consumption: standard preheating input power is 1500 W. No comparison tables take this consumption into account!

Leaving aside the money that preheating burns, its consumption significantly affects the energy balance of a low-energy house. If the house uses photovoltaic electricity generation and battery storage, preheating significantly reduces the part of the night when the house is independent.

The Big Magic ventilation unit remains fully functional even in freezing temperatures down to –20 °C, without preheating or other frost protection.

The uniquely designed silent mechanism changes the direction of air flow in the heat exchanger in an instant. The previously formed icing is defrosted by fresh supply air, which is thereby also humidified. At the same time, icing forms on the opposite layers. The switching cycle is repeated continuously at a precisely defined time interval.