Couple ventilation/heat recovery/air/water heat pump?

Good morning,
we are installing a controlled ventilation system with heat recovery and an air/water heat pump in our little house.

Doesn't it actually make sense to couple the heat from the exhaust air in winter with the air/water heat pump, especially since it has to heat the domestic hot water significantly in winter due to legionella elimination in the domestic hot water tank? Or, conversely, is that not effective because less heat is returned to the building through the ventilation and the heating system then has to work more?

Hi,
apart from the fact that your legionella control should not only run in winter, your idea of using the waste heat from the ventilation system is basically fulfilled by a so-called heat exchanger or heat recovery system. However, this cannot work miracles either, and on a cold day, about 9° warm air still easily escapes from your place to the outside.

Whether it makes sense to position this exhaust air outlet in such a way that it is in the intake area of the air-water heat pump... I don’t want to calculate it, and I can’t regarding the enthalpies with different air humidities – but just because the operating times of these two devices are not synchronized anyway, it only makes limited sense.
Moreover, you are blowing your slightly dusty indoor air onto the cooling fins of the air-water heat pump – also not very clever.
This indoor air, in turn, is very humid (yes, even if it feels so dry inside for you in winter... when this "dry" air is cooled, it becomes "relatively" highly humid again. Blowing that against your air-water heat pump leads to increased icing – more defrosting cycles with energy consumption – also not desirable.

In a completely insulated system, where it becomes scientifically necessary to conserve every watt-second, that would be an idea... otherwise, it is rather a trick similar to heat recovery in wastewater systems.
You can also overdo it, and there are enough more important parameters to consider on the way there.
A proper heating load calculation and a hydraulic balancing, for example.
ks

Hello,

...Doesn't it actually make sense to...

A air source heat pump might be completely pointless. What is the actual demand (power, energy) for heating and hot water?

Best regards