ᐅ Screed drying using a ground source heat pump with trench collector

Hello,
I installed a ground source heat pump with a trench collector for my building project in Brunnthal near Munich.
So far, everything has gone excellently.
However, a discussion has arisen regarding drying the screed using the heat pump and trench collector, specifically about the supply temperature for screed drying.
Our heating contractor used a maximum supply temperature of 45 degrees Celsius (113°F) for the screed drying. This temperature was reached without any problems. The 45 degrees corresponds to the maximum temperature of the built-in screed drying program of the Vaillant heat pump. We did not use the program itself, in agreement with the site manager, because an accelerator was used in the screed and the screed drying program would have taken too long. Therefore, the temperatures were manually adjusted.
The site manager now believes that a supply temperature of 55 degrees Celsius (131°F) should have been used for screed drying, which is 10 degrees higher. This temperature is based on the manufacturer’s specifications for the screed/accelerator, although this specification is not entirely clear, as it requires a maximum supply temperature of the heating system but no higher than 55 degrees. According to Vaillant, the ground source heat pump can practically reach up to 58 degrees Celsius (136°F).
However, the heating contractor says he cannot guarantee such high temperatures because this could cause freezing of the trench collector, which in turn could damage the collector, potentially rendering it unusable.
I also found various warnings about this on the internet.
Does anyone have experience with using a ground source collector (especially a trench collector) for screed drying? Could someone provide information about the maximum supply temperature that can or should not be exceeded with a ground source collector (especially a trench collector)?

Thank you and best regards

Tauben1a

Depending on the layout and spacing, the collector doesn’t seem very large (By “forum type,” do you mean loops about 1.5m (5 feet) deep in the ground?). There is still a significant lack of information regarding the installation and the heating energy requirement for warming up. For me, underfloor heating at only 35°C (95°F) already consumed 2200 kWh of heat, even though the outside temperature was relatively warm. When you extract a year’s worth of energy from the ground in just a few weeks, I consider that critical. Judging by your heating load, underfloor heating may require a lot of energy in your case. If you do this shortly before the cold season, the ground won’t have time to regenerate (even if it hasn’t fully frozen yet), and by winter at the latest, the brine temperature will drop significantly, possibly below freezing. If the collector is designed just barely to meet the normal heating demand without any reserves, I would be very cautious. In that case, it’s better to heat the screed directly with electricity. For situations like this, it’s advisable to budget for additional operating costs, which should realistically be expected anyway.

Hello Saruss, thank you for your reply. Exactly, the trench collector of the Formus type is constructed with coils, however, the frame is about 3 meters (10 feet) high and was installed vertically into the ground beneath the house, starting at a depth of 1 meter (3 feet).

Borrow an electric heating cartridge and connect it to the heating circuits instead of the central heating system. You can also heat it up to 65°C (149°F).

The screed manufacturer requires the maximum achievable temperature of the heating system, but no higher than 55 degrees Celsius (131°F). This limit would be met with 45 degrees Celsius (113°F), so why is there a discussion? The most important thing is that the screed dries properly, and if it can do so with a supply temperature of 45 degrees Celsius (113°F), then everything should be fine… or am I missing something?

Hello One00, very good point, I’m wondering about that too. I’m not a construction expert, but I am building now. I researched online and only found that the screed should have reached sufficient dryness. According to the site manager, a moisture measurement was carried out and the screed is dry enough. The site manager has not yet explained the reasoning behind the requirement that a maximum temperature of 55°C (131°F) must be reached (for example, if any damage has ever been proven to be caused by this). The problem is that the site manager does not want to give the tile setter approval, which would leave the risk with me if the tile setter starts anyway.
Regards, Tauben1a