Moisture-proof Control of Balanced Ventilation Systems with Rotary Wheel Heat Recovery in Single Family Detached Houses

Single family houses with balanced ventilation have become more airtight, heat recovery efficiency has increased, and rotary heat exchangers have become the most common. All these changes combined increase the risk of moisture convection damage when it is very cold outside. However, theoretical studies have shown that it is possible to control airflows and rotor speed, in such a way that the risk of moisture damage is minimized. In collaboration with the ventilation industry, this project has developed a dynamic method of testing, in a controlled laboratory environment, how air handling units control systems can handle realistic variations of internal moisture generation in a moisture-proof way. The methodology means that an air handling unit with its control system is connected to a hardware-in-the -loop test facility that can in real time simulate an installation corresponding to a real house with different outdoor temperatures and internal moisture generation. The output from the test is how the moisture content varies in different rooms, extract air and supply air, as well as the variation of supply and extract air flow rates. Ventilation with different control strategies have been tested. In the project it has also been studied how the moisture recovery in rotary heat exchangers with different moisture-recovering properties varies depending on rotational speed, airflow, and outdoor temperature. It has then also been possible to verify previous theoretical calculations. The main conclusion is that by controlling the rotor speed and the air flows, the moisture contents in the indoor air can be controlled during periods of high moisture load.