Junkers Geothermal Heat Pump STM-100 Experiences

Hello everyone,

we have commissioned a geothermal heat pump with deep drilling from our developer.

The heating engineer wants to install a Junkers STM-100 as the model.

The whole system is combined with a hot water storage tank and a buffer tank for the underfloor heating.

Then a Wolf CWL 300 or Wolf 400 ventilation system with heat recovery is also to be used.

Since we have absolutely no idea about this topic, it is very difficult for us to assess this matter.

In principle, we naturally trust the developer and the heating engineer, but experience from our last build has shown that some reasonably intelligent questions can also contribute significantly to improving the resources used.

Does anyone have a tip on what we should pay attention to?

Many thanks

Ostsee

...we commissioned a geothermal heat pump with deep drilling from our builder. The heating engineer wants to install a Junkers STM-100 as the model.

Which heating load according to DIN 12831 was determined? Are the thermally effective air volume flows (air volume plan according to DIN 1946-6) of the controlled residential ventilation sufficiently considered there? What demand (energy, power) was determined for the source dimensioning?

...and a buffer tank for the underfloor heating.

With brine heat pumps, a buffer (what is meant here – separating, serial, parallel – ?) is a yearly performance factor "killer" and should be avoided if at all possible!

...In principle, of course, we trust the builder and also the heating engineer, ...

I would not be so optimistic about that

...Does anyone have a tip on what we should pay attention to?

Yes, have the complete planning documents checked (have them reviewed)

best regards

Hmm.. let's see, we have an energy saving regulation certificate according to DIN 4108-6 and DIN 4701-10.

Usable area is ~ 240 sqm
Volume ~ 760 sqm
Envelope ~ 590 sqm
Windows ~ 52 sqm

If I understand the sources correctly, the energy consultant comes to the following figures:

Sum of Heat
Domestic hot water = 1446 kWh/a
Heating = 1151 kWh/a
Ventilation = 0 kWh/a

Sum of Auxiliary Energy
Domestic hot water = 218 kWh/a
Heating = 663 kWh/a
Ventilation = 724 kWh/a

Sum of Primary Energy:
Domestic hot water = 4326 kWh/a
Heating = 4716 kWh/a
Ventilation = 1882 kWh/a

According to the builder, the buffer tank is required to guarantee a certain circulation volume.
I admit that I did not really understand the whole thing
According to his information, we would have to leave one or more heating circuits open and unregulated if no buffer tank is integrated into the system...

Hello,

According to the developer, the buffer tank is required to guarantee some circulation volume....

This is currently the newest phenomenon; almost every second interested party comes with such a statement .... in most cases paid for expensively but not really meaningful

€uro will be able to explain the rest to you better than anyone else here at the HBF.

Kind regards

Hmm.. let's see, we have an energy saving ordinance certificate according to DIN 4108-6 and DIN 4701-10....

This certificate only serves the purpose of deciding "on paper" primarily energetically about the admissibility of the project! If you take a closer look at the fine print, you will find that real consumption cost estimates or heating system dimensioning are not permitted according to these specifications!

....According to the builder, the buffer tank is required to guarantee some circulation volume.

It will be a general contractor/general planner, not a builder. In addition, he has probably contracted the cheapest subcontractor he could get for heating and hot water preparation. This subcontractor is apparently not capable of proper dimensioning. Here, a parallel buffer? is probably installed as a last resort because the hydraulics are not mastered. This costs investment and efficiency!

....I admit that I did not really understand the whole thing

That is always good for a salesperson

...According to his statements, we would have to leave one or more heating circuits unregulated unless a buffer tank is integrated into the system...

Technical nonsense! Have all calculation documents shown to you beforehand! They probably do not even exist.

best regards

Thank you already for the help

What exactly should I ask for or which documents should I request?

And does our developer or main contractor have to provide us with something like this, or do I as the client actually have any leverage to make demands?