ᐅ Functional heating – Implementation and Responsibility?

Hello everyone,

In our new development area, we are in a situation where we are connected to a thermal network and provided with a brine-water heat pump by the supplier. We pay for the amount of brine used, but not for the electricity required to operate the heat pump. We are building with a turnkey construction company and have just had underfloor heating and a cement screed installed. Now the question about functional heating (after 21 days of rest) arises. According to the supplier, the maximum supply temperature for the heat pump is 33°C (91°F). The DIN EN 1264-4 standard refers to the “maximum design temperature” regarding functional heating, which should be exactly this 33°C (91°F). On the internet, however, the value 55°C (131°F) is often mentioned, but I assume that refers to typical gas or oil heating systems.

The supplier states that we are not allowed to do functional heating with the heat pump. Instead, they offer to rent a temporary electric heater (hot box) for that purpose. Since using the heat pump for functional heating is otherwise common practice, I asked for clarification. It turned out the supplier does not want the electric heating element to activate during functional heating because they would have to pay the electricity costs. I then pointed out that the heat pump should easily be able to reach 33°C (91°F), as it is designed for that. The responsible person then said that we are allowed to do the functional heating with the heat pump after all, which is a bit confusing. However, he advised against it because the floor in the utility room is not yet tiled or at least not properly grouted, and the heat pump could potentially cause slight indentations in the screed. Our tiler also advised against installing the heat pump early because he would have to come back just to tile the small area where the heat pump is placed. Also, since we want the same wooden plank tiles throughout every ground floor room, this small area in the utility room would determine the entire tiling pattern for the ground floor.

So, for now, we decided to use the temporary electric heater. Our construction manager stayed out of this topic so far because it is not related to the construction company. Later, he mentioned that he usually advises homeowners to place the heat pump on an aluminum base and then tile around it. That sounded quite reasonable, and I felt poorly advised by others before.

How would you handle this?

Since we are already late in the schedule, it is possible that the heat pump cannot even be installed early or the power connection might come too late, and we would have to use the temporary electric heater to meet the timeline.

However, using the temporary electric heater also presents challenges. For one, we do not yet have an electrical outlet in the house. The construction power box is about 60 meters (197 feet) away, and heavy-duty extension cables (do they even come in 60-meter lengths?) are often stolen. Also, there is the question of operating the temporary electric heater. We can pick it up, and they will probably explain how to operate it. According to the construction manager, the construction company is not responsible since we do not get the heat pump from them, so we have to manage the functional heating ourselves. However, I have concerns about connecting it myself to the water pipes, etc. I worry I might damage something or operate it incorrectly. It feels too risky for me.

I read the following:

- “For floor, ceiling, and wall constructions, functional heating and cooling according to DIN EN 1264-4 serves as proof of a defect-free installation by the heating installer and screed layer [...].”

- “Heating up an underfloor heating system is thus a functional test of the heating installation [...]. This process is part of the contract work of the heating installer according to VOB.”

This actually sounds like it is not my responsibility but that of the construction company or a specific trade. So who exactly is the heating installer—the one who installs the underfloor heating or the one who supplies the heat pump?

I am a bit overwhelmed and would appreciate expert advice!

Thanks and best regards