LWZ 8 CS Premium combi made of air-water heat pump, controlled residential ventilation and hot water storage tank

Hello friends!

Originally, we were thinking of a brine heat pump. Also because we thought that with an air-water heat pump we wouldn't qualify for the funding.

However, during the conversation with our heating engineer plus a representative from Stiebel Eltron, we were told that we can meet the BAFA funding requirements with an air-water heat pump as well and could therefore save the significant additional costs for drilling.

We were now recommended the LWZ 8 CS Premium from Stiebel Eltron as a combination unit. Our heating load is 7.6 kW (we had it calculated externally), so that would already fit. What we like is that with the LWZ 8 CS Premium we would not have an outdoor unit.

Now my specific questions: in the conversation, the combination unit was strongly promoted. One argument was that the exhaust air from the integrated controlled residential ventilation is also used energetically for heating purposes. In addition, everything is built into this device, which keeps the work effort for the installer, etc., more manageable and simpler. From your point of view, is there anything speaking against the combination unit?

The alternative would be 3 separate units (heat pump, whether brine or air / controlled residential ventilation / hot water storage)...

Thanks

The exhaust air is also routed through heat recovery in a controlled residential ventilation system that is not directly integrated into the heat pump, reducing heating costs.

One device for everything may simplify installation for the heating engineer, but it also ensures that the investment flows only to the one manufacturer.

Ask yourself or Stiebel Eltron what happens if the heat pump breaks down, can you still use the ventilation system? Or do you have to replace everything even though only the heat pump is defective?

What happens if you are absolutely not satisfied with the all-in-one solution and want to replace it after 15 years? These devices are optimized for space so that when replacing and switching brands, you have to install another all-in-one solution because your technical room no longer allows it without gutting it. This also creates customer lock-in.

I would always prefer separate solutions, i.e., a separate heat pump with a separate controlled residential ventilation system. There are also manufacturers who offer both if you don't want different manufacturers/brands.

I find the device to be significantly more attractive than the separate solutions. The installers do not have to worry about the cables between the devices (which is quite complex and expensive) and less space is needed as well. I also do not think it is likely that the device will break down quickly. Stiebel Eltron is the market leader, the devices are designed for a very long lifespan, and the quality is good.

The alternative would be 3 separate units (heat pump, whether brine or air / controlled residential ventilation / hot water storage)...

Just have everything calculated for you. Take whatever is cheaper. Whether you choose the integral unit or three separate ones is more a matter of philosophy.

Just have everything calculated for you. Whatever is cheaper, you take that. Whether you take the integral device or three separate ones is more a matter of philosophy.

Alright, that's a good idea. I thought there might be clear arguments. But opinions are divided here as well.

I have now read that you should pay attention to a proper bypass in the controlled residential ventilation. However, I can't find anything in the device description. Do controlled residential ventilations nowadays all have such a bypass to bring cool air into the house at night in summer without heat recovery?

Do controlled residential ventilation systems nowadays all have such a bypass to bring cold air into the house at night in summer without heat recovery?

No, of course not. It is an extra. Of course, most have it "by default". But who knows what you actually get there.