Integral device Stibel Eltron LWZ 504 with central supply air

Hello everyone,
we will be moving into our own home soon and also have an LWZ504.
The heating technician will instruct us on the system next week and I have already read the manual.
We have a KfW40 house, 2 people, and an additional tiled stove that should be used regularly in the evenings and on weekends.

The system has been running for two weeks with the heating technician’s default settings:
- Heating program: Heating circuit 1 at 21 degrees Celsius from Monday to Sunday, 24 hours each day.
- Hot water program: Setpoint 55 degrees Celsius from Monday to Sunday, 24 hours each day.
- Ventilation program: Day ventilation at level 2, night ventilation at level 1

I know that heating behavior varies from person to person and that efficiency depends on many factors.
But still, here is a question to the experts or owners of an LWZ 504:
Do you have any recommendations regarding optimal settings for the start?

I think 21 degrees for the heating program is okay, but can I optimize this further?
From Monday to Friday, usually no one is at home between 8 am and 5 pm. Does it make sense to set the operating time for heating circuit 1 from 3 am to 7 am to save energy costs? On the other hand, the outside temperatures are higher during this time, and thus the efficiency of the heat pump is better. Or am I mistaken here?

Regarding the heating curve, I am completely unsure; the technician has already entered recommended values here. But maybe someone can also provide recommended comparative settings?

For the hot water program, 55 degrees seems okay for now. We are currently a two-person household and shower either in the evening or in the morning. Can I optimize the times here? Actually, hot water preparation during the day should be more efficient due to higher temperatures, right? However, as far as possible, I want to avoid using the electric heating element.

In the warmer months from May to August, I will probably switch the operation from automatic to hot water mode anyway, because heating is usually not needed, and in case of temperature drops during this time, we still have a tiled stove.

Thank you very much for your experiences, suggestions, tips, and tricks.

The hot water temperature is quite high, we have set 44 degrees Hyst 2, that is more than enough and should be significantly cheaper. I have adjusted the heating curve according to the points base point and slope. That is also how it is stated in the manual. Our heating runs continuously, a reduction does not make sense afaik. I would wait for the appointment with the technician in your place. Strangely not directly with SE? Then you can slowly work your way down. I was able to significantly reduce the base point and the slope.

Thank you Ares for your response. By technician appointment you mean a subsequent appointment with the maintenance person. The maintenance is not carried out by the installer in our case and we first have to meet with them regarding the different maintenance models in December. We will only receive the contact details during the briefing appointment with our installer. I need to take a closer look at the heating curve or then go through it with the person responsible for maintenance.

With us, the heating engineer installed the heat pump, etc., Stiebel themselves then set up the system during an appointment, started the heating program, and a week before the house handover, Stiebel also gave the instruction on the system.

The maintenance is not yet decided for us; the heating engineer wants €500 per year, which I simply reject, as even Stiebel themselves are cheaper.

For you, only the base point and the slope actually matter with the heating curve. If it is too warm during the transition period, simply lower the base point a little. Then wait two days and see if it was lowered enough. You can find this under troubleshooting in the manual.

I am also interested in the LWZ504. A question for the people who find the ventilation too loud: - Were silencers installed that Stiebel offers as accessories? - Where is the system located? - Construction type of the house? Generally: Are there comparable alternatives? Also with outdoor installation?

Hello Ares,

thanks again for your reply.
Regarding the technician appointment, something went wrong on my side, because my heating installer said I did not have to be on-site when the Stiebel technician sets up the heat pump and starts the screed program. Unfortunately, I relied on the heating installer here. During the screed program, some error codes also occurred, which have at least been fixed by now. As I said, the instruction is done by my heating installer; if I want an instruction from the Stiebel technician, it costs extra. We will now bite the bullet because my heating installer also does not do maintenance, as he is not very familiar with the device. Previously, it was said that they had already installed many of these systems and only had good experiences so far. Now the damage is done, but an instruction by a technician who knows the system well is absolutely necessary for me. So I will deal with the heating installer again and look for a satisfactory solution.


Since we have not moved in yet, I cannot say much about the noise level. I currently do not find it too loud during the day operation (level 2); how it might be at night in the bedroom remains to be seen.
The system is located in our basement (without a silencer but with a sound-optimized air hose), so the operating noise certainly does not bother us in everyday life.