ᐅ Cabinet with air-to-water heat pump and water storage tank. Does anyone know this system?

Lucrezia schrieb:

The only alternative I know of is wall heating (which would be perfect with clay), but it is considerably more expensive than underfloor heating.

You should have a room-by-room heating load calculation done anyway, and then plan the heating surfaces accordingly. Maybe your energy consultant can help with this. You can then add wall heating selectively alongside underfloor heating where necessary, depending on the floor or other factors. I would only skip underfloor heating if it is harmful to the floor; otherwise, it always provides some heating output.

In our case, the normal air exchange rate is sufficient to heat the house. If there is a higher heating demand, this can only be met by warmer air and/or a higher air exchange rate.
This raises the following questions:
- How comfortable is it to sit or stand next to a hot air blower in that situation?
I could set the system to the highest level (which it has never been except at night during summer). Temperature might be difficult since I activated the summer bypass yesterday.
- Higher electricity costs because the mechanical ventilation with heat recovery runs at full capacity more often
- Higher electricity costs because the compressor runs more
- Does the emergency/additional heating turn on faster?
I would imagine so.

I have no experience with the effectiveness of underfloor heating combined with thick wooden floors.

@boxandroof
It is not a simple exhaust air heat pump.

@Lucrezia
The service team is coming next week, but I won’t be there to assist.
In any case, it’s interesting to consider what happens if, for example, the hot water boiler breaks down. Does everything need to be replaced (as was rightly pointed out here), or are there spare parts available?

haydee schrieb:

Difficult, I activated the summer bypass yesterday.

Just out of curiosity, can the bypass switch automatically? In our case, the heat recovery system doesn’t operate at night, but when it’s warmer outside, the supply air is cooled down through the heat recovery unit.

It doesn’t really make much difference, of course; we’ve noticed that air transports very little heat.

haydee schrieb:

It’s not a pure exhaust air heat pump.

Yes, but in connection with controlled mechanical ventilation with heat recovery, there’s no real advantage in using the exhaust air for the heat pump, meaning it’s unnecessarily complex.

haydee schrieb:

The boiler for hot water is broken? Everything has to be replaced (

The answer will probably be that spare parts are available, of course. But think ahead 10 to 20 years. Then everything will have to be replaced because repairs won’t be worthwhile. Will you then be installing “simple” devices from any manufacturer or end up paying something like 20k again?

What do you mean by that?
I remove the heat exchanger and insert the summer cassette (pieces of polystyrene). After that, I need to tell the system that the summer cassette is installed.
This should be the case for all combined units of this brand, for example the LWZ 504.

Active cooling, meaning the supply air is cooled, is not possible – whether this will be available in the future or if current standard units already have this feature, I don’t know. I didn’t miss it last year.

If the outdoor temperature stays 2 hours above the desired indoor temperature, the system shuts off; if the outdoor temperature drops below the current indoor temperature, it switches on. Last year, the indoor temperature was usually around 23°C (73°F). Active cooling is not necessary, but it would certainly be comfortable.

Heat recovery is about 90%, the rest is managed by the pump. This sounds logical to me and not unnecessarily complex. The remaining heat has to come from somewhere. Pure electric heating at double-digit subzero temperatures (Celsius) is good news for the electricity provider.
How does it work with separate controlled residential ventilation and an air-to-water heat pump?

Yes, in 20 years the patents will expire, Passive House standards will become widely available, and there will be free choice. If one wants, they might stay loyal to the brand because, for example, the service fits well.

haydee schrieb:

I remove the heat exchanger and insert the summer cassette (pieces of polystyrene).

Understood, thanks for the information.

We "cool" passively through heat recovery, which uses the cooler indoor air to slightly lower the warmer incoming air just below room temperature. When it’s colder outside, the heat exchanger is inactive. But this is purely theoretical with little practical effect. Our mechanical ventilation with heat recovery system operates with a rotary heat exchanger, so it’s somewhat unusual, with both advantages and disadvantages.

If I understand correctly, the heat pump uses either the exhaust air or exclusively the outside air, like a conventional air-source heat pump.

Your heating system provides around 3.x kW solely from the heat pump. For our house (150m2 (1,615 sq ft), rated between KFW 55 and 40 standard with mechanical ventilation with heat recovery), that is sufficient to avoid activating the electric backup heater. On paper, it might not seem enough, but in practice it is. I cannot assess how much the efficiency is reduced compared to water-based systems or how warm the air would need to be in our location. I’m curious about your actual energy consumption. There are other cases where the company name alone suggests it’s unreliable.