Integral device Stibel Eltron LWZ 504 with central supply air

Hello everyone,
I would like to revisit the topic.

About our house:
KFW 55 house, heating load approx. 3.5 kW, heated building volume approx. 500 m³, size 140 sqm, 2 adults 2 children...

So far, an LWZ 304 Sol was planned for us. This is now no longer available and we have the offer to get an LWZ 504 for free.
Unfortunately, I have the feeling that the 504 would be way too big.
The question is, is that correct? And if so, is it a problem?

Due to the structural preparations, only an LWZ is possible, and I find it very difficult to assess whether I should take the 504 despite possible oversizing given these conditions. What do you think?

Best regards

Hello everyone,

I have had the LWZ 504 for a month and it is - based on everything I have read here - properly installed. Decoupled on a metal base, two fairly large silencers for supply and exhaust air, programmed and adjusted by a Siebel-Eltron installer.

I am currently completely stressed out because of the noise development of this "monster."

The system can simply be heard throughout the entire house - day and night - 24 hours a day - 365 days a year - always(!) ... unless I switch it off manually.

We only operate the ventilation function of the LWZ 504 on the lowest level 1 because the noise otherwise even disturbs watching TV - not to mention concentrated work in the office or falling asleep peacefully in the evening. The actually calculated level 2 for normal air exchange is no longer used by us at all because the device runs significantly louder then. The ventilation ducts carry the sound into every single room. The supply air is noticeably louder than the exhaust air, i.e. in the living areas (living room, bedroom, guest room, children's room, office) the noise development is highest. In bathrooms and kitchen, however, (at least on level 1) you hardly hear anything.

Currently hardly bearable, however, is when the heat pump (heating function) is running, which can also be the case 24 hours a day in the cold months. It then sounds like a vacuum cleaner directly in front of the device - and this noise is also transmitted throughout the house. Of course not as loud, but still a clearly audible, low-frequency humming, buzzing, rustling. It simply sounds unpleasant and disturbing since the entire house sounds like heating/ventilation, i.e. typical "basement noises."

Whether something can still be improved in our system regarding noise development I do not yet know; I am in contact with the installing specialist company, which, however, is very reserved. As of today, I can only advise against the installation of this device (LWZ 504) because of the noise development.

Best regards A. Rösner

Hm, best check the filters first (both on the WT, all in the rooms). If they are full, the system will be a bit louder. However, the difference is minimally noticeable but not disturbing. The system also gets a bit louder with hot water if you stand directly in front of it, but that is not really significant either. Overall, it sounds like something is still not quite right. I am quite sensitive; in our previous new-build apartment, I could hear the gas boiler installed on the other side of the 4-family house. I don’t hear the 504, and that one is closer to our bedroom. What air exchange rates are recorded for each of your levels? What are the intercept and the slope? What temperature is your hot water?

What I find really strange is that the heat pump runs 24 hours straight?! Ours runs maybe a total of 2 hours a day for heating during the transition period and another 1.5 hours for hot water. The rest of the day, nothing happens except ventilating. And it’s really quiet. Even on level 2 out of 3. Something definitely doesn’t seem quite right?!

The system can run for that long already. It modulates while doing so. We are still heating as well. It is supposed to snow again in the next few days ... currently no 10 degrees during the day.

Regarding the topic:
What are your ventilation levels?

Nothing happens there for the rest of the day except airing. And that is really quiet. Even at level 2 of 3. Something really seems to be not quite right?!

At level 3 with 300 m3/h you can already hear something near the valves. Level 2 for us is 160 (during the day) and at night level 1 is 110