Split air conditioning and controlled ventilation with heat recovery

We already have a central cooling system in our [Kontrollierte-Wohnraumlüftung] or air-to-air heat pump. However, it doesn't do much. It circulates 300m3 per hour. Therefore, we wanted to add a 7KW unit for support, which is capable of circulating 1200m3 of air and cooling it down in the process. I can imagine that this might work if it runs constantly and tries to maintain 22 degrees in the house. That would be 3 degrees less than what the normal central cooling system can achieve. That should be possible, right, or am I mistaken?

How do you cool centrally? Refrigeration unit and chilled water system in the controlled residential ventilation? Or do you mean through the underfloor heating? That can buffer only 2-3 degrees anyway and does not dehumidify. Air conditioners at multiple points can be controlled more precisely and the distribution is also better. How big is the house? Better 2 x 3.5 kW than 1 x 7 kW.

Hi,

That should work, or am I making a mistake?

Unfortunately, it won’t help much. The controlled residential ventilation simply doesn’t have enough airflow to "transport the cold" (correctly: to transport the heat out). What you can do is integrate a small air conditioner into the intake duct and use it to dehumidify the incoming air. The unpleasant thing in summer is not really the temperature but the high humidity. 25 degrees in the house at 65-70 percent means bad sweating, 25 degrees at 45 percent almost feels cool.

Best regards,

Andreas

That would be, for example, the variant with a refrigeration unit and a chilled water system. But even here, there is a dew point problem with the pipes. And to continuously cool 300m3 per hour of flow, you already need considerable power. If it is 30 degrees or more outside, you first have to cool this down. I recommend multiple indoor units as multi or single split. Much more power is delivered, it is more efficient, and can be controlled more precisely. Controlled residential ventilation should be turned off on very hot days.

How do you cool centrally? Chiller and chilled water unit in the controlled residential ventilation? Or do you mean via the underfloor heating? That can buffer only 2-3 degrees anyway and does not dehumidify. Air conditioners at several points can be controlled more precisely and the distribution is also better. How big is the house? Better 2 x 3.5 kW than 1 x 7 kW.

The heat pump via reversing the refrigeration cycle. We do not have underfloor heating. It is a pure air-to-air heat pump with ventilation and exhaust air with heat recovery. Our house is 168 m2 and built open.

And how does the cold then get into the controlled residential ventilation system or house? For 168m2, 7kw will not be enough for you. Even if it is shaded.