New single-family house, gas or heat pump, target KfW55

who put together your system from ochsner? Do you have a buffer tank included? I have an offer for the GMLW9 and the outdoor evaporator, 1x domestic hot water buffer and 1x buffer tank (necessary for the regeneration of the outdoor unit) for just about 20k€. The WRL is extra for me.

The offer was prepared by my friend who is an installer and who sells Ochsner alongside Stiebel Eltron. The package includes:

Split evaporator MSV14 Millennium GMWL9 plus air/water heating heat pump Ochsner O-Tronic Easy PLUS OTE flow sensor display with screen remote control heating cooling heating cooling module buffer tank PU300NOROF 3.75 kW electric heating element 323DK air/water domestic hot water heat pump installation and commissioning

Regarding the calculation basis of the energy consultant:

Calculation program: Energieberater 18599 7.4.2 Hottengroth Software-

The following standards and regulations were considered in the calculation:

DIN EN 832:2003-6
DIN V 4108-6:2003-6
DIN V4701-10/A1:2006-12

Regarding the first DIN it says here:
Thermal behavior of buildings - Calculation of heating energy demand - Residential buildings

Does the installer not have all the data for the design with this?

Hello,

Here are the details from the KFW application....

To achieve KFW 55, the following must be met for the building:
Qp <= 46.04 kWh/(m2a)
H'T <= 0.26 W/(m2K)
provided the determination for the reference building is correct ;-)
Strictly speaking, both requirement values are missed here. H'T only slightly. An optimization of the thermal building envelope might be possible here.
Regarding Qp, clarification is needed. The reference building includes a solar thermal system for hot water with theoretical coverage ratios, which are practically never achieved with the standard 0815 systems sold by GU/GÜ[B]. An absolute deception! Especially penalizing builders who invest considerable additional effort in building insulation!
In the present case, however, it should be examined overall to what extent this actually makes economic sense. Subsidies (KfW) are not given away as often assumed but are actually merely a "band-aid" for the associated increased investments.

There are cases where it is economically worthwhile to achieve a subsidy status. In others, it can become a money pit. The latter especially when significant discrepancies arise in practical implementation (planning, execution) compared to the usual beautification on paper. There are plenty of examples for this ;-)

....Would it be possible to achieve KFW 55 with a heat pump and photovoltaics?

Probably yes, but that is of little use if H'T is not achieved!

...Are these generally good values or only mediocre to poor?

What is good or bad? According to what evaluation standard? If the actual demand (performance, energy) for a defined building and user behavior is not known, this question can hardly be answered reliably.

best regards

For me, the field service technician from Ochsner configured it directly; it only differs from your offer in that I have a second buffer instead of your wwwp. Check on your side if you have the weather protection grille and the refrigerant lines included. Since I am Austrian, I am not so familiar with the conditions in Germany, only from what I quickly saw, I would be in Germany at Kfw 40-55.

He should have it, but ask him about your monovalence point, where it lies. If he doesn’t have it, then he just put something together and didn’t look properly. According to EN12831 (simplified), I have 5.76 kW heating output under my local conditions (standard outdoor temp -12.3°C). When I then look at the characteristic curve, at 35°C flow temperature and 6 kW output, I come to about -12°C at a COP just under 3. That one air heat pump performs better than others upward is pure physics; only at these cold points must it work cleanly, not at 0°. Otherwise, it becomes an electricity guzzler. Of course, if you don’t really know your way around, you are more or less reliant on the planner.

I am of the opinion that one should not forcibly achieve any class (on paper), but really have everything put together cleanly. What’s the point if you reach KFW 55, but due to a wrongly sized heat pump, you have to heat with the electric heater below -4°C or so???

Good morning,

the price includes the complete installation, so the pipes and the weather protection grille are also included.

I just spoke with my heating technician:
He will get started and will carry out a heating branch calculation together with Ochsner. The basis is the calculation of the energy consultant who submitted the KfW application.
The technician has already installed several systems in this form and has been able to gather good experience so far.
In his opinion, it is rather energetically nonsensical to use a single heat pump for both heating and hot water.
The reason is the competing temperatures.
The pump heats to 35°C for the flow, then to 55°C for hot water, and then back down, and here it sometimes happens that 55°C reach the heating circuit, causing the heating curve to start oscillating.

I have preliminarily carried out the heat load calculation with an online calculator.
At -12°C, I come to a heat load of 4700W.
According to the datasheet, the pump delivers 6kW at -10°C.
Could that be cutting it close?

Regards

And to come back to the original question: Assuming a heating load of 5-6kW, is a heat pump or rather the gas condensing boiler to be recommended?