Supply of hot water, instant water heater yes/no

Hello Havejan, you surely have a wooden house from Weberhaus, right? The interior walls there were already made of drywall panels at the factory? These are usually not plastered, but only filled (with or without painter’s fleece) and directly wallpapered or painted. We also have an LWZ in our house. Your points were all discussed during the consultation. It was even pointed out that after a full bathtub fill, a second one isn’t possible, but this heating system doesn’t really cause problems. 44 degrees are more than enough to wash dishes?! Do you want boiling water from your faucet? @ €uro: Havejan had raised the issue of legionella. Is this really relevant in a single-family house, that legionella can settle in water pipes under 60 degrees? Naively, I assume that Havejan, like me, doesn’t have a preheating installation because of Kfw.

Hello Wastl,

you surely have a wooden house from Weberhaus? The interior walls there were already factory-fitted with drywall boards? Normally, these are also not plastered, but only filled (with or without painter's fleece) and then wallpapered or painted directly.

yes, we have a wooden house with gypsum. at least half of it has been removed again and reattached.
Normally, wallpapering is also done, but we wanted a fine plaster inside. Since Weberhaus did not want/could not deliver the paint (we had the "recipe"), we removed the plaster. Now Weberhaus says that the painter's fleece does not belong to the filling and that it was the job of our painters. When we asked whether the filling was finished enough so that the painter only had to sand and clean up, unfortunately Weberhaus hides behind the statement that nothing is written down on paper.

We also have an LWZ (heat recovery ventilation system) in our house. All your points were discussed during the consultation. It was even pointed out that after one full bathtub fill, a second one is not possible, but this heating system actually does not cause problems.

We were not informed about this, nor about the water temperature. At the moment, the heating system does not cause any more problems.

44 degrees is perfectly enough to wash dishes?! Do you want boiling water from your tap?

44 degrees are enough for dishes, yes, but not for greasy pans and oven ceramics. When I fill our large sink, which is ceramic, the water is only 39 degrees. That is not enough and certainly not enough to keep the pipes clean of soap/grease residues.

@ €uro: Havejan had raised the issue of legionella. Is it really relevant in a single-family house that legionella can settle in water pipes below 60 degrees? I naively assume that Havejan, like me, does not have pre-heating installation because of KfW.

It is not very likely with legionella if the water flows through all the pipes, but here in France it is a law that heating must take place weekly.

I have now reached the point that I have broken off communication with Weberhaus. Weberhaus refuses to be customer-friendly and, as mentioned, hides behind the fact that certain things are not documented on paper. I am completely done with this company and will recommend them to no one. They call themselves customer-friendly, but their customer service is not even able to respond normally to emails/phone calls. I keep receiving letters by mail that take at least 5 days to arrive. I could go on for a very long time but I no longer want to. Maybe I will list my experiences in a separate topic here in the forum.

....It is not very likely with legionella if water flows in all pipes, but here in France it is the law that it is heated weekly....

The legionella issue is a certain "grey area". They become critical, if present, especially with pulmonary exposure (inhalation of water vapor or mist). In Germany, weekly heating of indirectly heated storage tanks to > 60°C combined with subsequent flushing of the supply lines to the taps has proven effective in practice. Meanwhile, there are new requirements (Drinking Water Ordinance), depending on whether it concerns small systems (single-family house, two-family house) or large systems. For the latter, an annual legionella inspection is required for storage sizes >= 400 l and water content <= 3 l between the outlet of the drinking water heater and the withdrawal point!
The hot water preparation must not be considered independently of the type of heat generator when heating and hot water preparation are to be operated alternatively with the same heat generator. Gas condensing (E-Gas!) units are today "modulation champions," provided they are properly sized (manufacturer, device selection), and can meet all requirements relatively well. Indirectly heated storage tanks are still mostly sensible here.
With heat pumps as a heat generator, the situation looks quite different. Especially in well to very well insulated buildings, the required output of the heat generator for heating operation is relatively low. For hot water, in bivalent, alternative operation, there is often a lack of necessary power for an indirectly heated hot water storage tank, which applies particularly to the combined solutions often sold by general contractors/system integrators. The solution here are "heat pump-friendly," indirectly heated hot water storage tanks from external suppliers.
Merely oversizing the capacity from the perspective of hot water preparation usually leads to a significant reduction in efficiency for heating operation and thus overall! Furthermore, the heat pump then only "lives" for a short time!
Alternatively, instant water heaters (fresh water stations) should be considered for use. In these, it is not the drinking water, as with indirectly heated storage tanks, but the heating water that is stored! However, the additional cost is not insignificant. As always, this must be weighed on a case-by-case basis. For high flow rate demands (e.g., rain showers), instant water heaters frequently fail if improperly designed!

Best regards,

Conclusion: Hot water preparation requires as detailed and precise system planning and sizing (basic evaluation) as heating operation, if one is interested in an overall economical solution!

Hello Jan,

I have now reached the point that I have broken off communication with Weberhaus. Weberhaus refuses to be customer-friendly and, as mentioned, hides behind the fact that certain things are not in writing. I am completely done with this company and will recommend them to no one. They call themselves customer-friendly, but the customer service is not even able to respond normally to emails/phone calls. I keep getting letters by mail that take at least 5 days to arrive. I could go on for a long time but I don’t feel like it anymore. Maybe I will list my experiences in a separate topic here in the forum.

Regarding your problems with your provider, I would like to advise you to consult a lawyer you trust and discuss the defects of the house with him. There are moments – unpleasant as they may be – when lawyers can often provide quick and unbureaucratic help. Your provider also fears bad publicity and will take care of your problem as soon as a lawyer is involved.

I wish you much success!