ᐅ Heating-up phase of the screed / floor screed window position

RotorMotor schrieb:

Do you think it is necessary to reach 60 degrees during functional heating if the heating system will only operate at a maximum of 35 degrees?
I have always read differently. DIN1264-4 also states to raise to the design temperature for 4 days.

There are two answers to your question:
1 (formally correct): Heating up to 60 degrees is required to maintain the warranty.
2 (practical/reasonable): Heating up to 60 degrees is unnecessary for a floor heating system designed for a maximum of 30-35 degrees.

KlaRa schrieb:

If both the drying phase heating and the preceding functional heating are not operated at the highest possible flow temperature, the screed can still reach readiness for floor covering, but due to the greater screed thickness between the heating elements, it will not be achieved within the required timeframe.
This means that when the floor covering is installed, the screed is not sufficiently dry in cross-section.

That is correct, but not critical. In that case, the heating period is simply extended, and any professional floor installer will measure the screed’s moisture content. Therefore, with a reliable contractor, the risk is effectively zero.

KlaRa schrieb:

Deviating from the guidelines, which represent the current state of technology as well as professional standards, significantly increases the risk of damage to the screed.

The problem is that these guidelines do not yet fully reflect floor heating systems with 30-degree flow temperatures, but rather apply generalized assumptions.

Conclusion: During functional and drying phase heating, you must reach 60 degrees to secure the warranty, unless the screed installer guarantees it at lower temperatures. Otherwise, there are no practical disadvantages, since the performance of the screed is tested at the maximum flow temperature (+5 degrees).

I must strongly disagree with @KlaRa that serious problems will occur if 60 degrees are not reached. The literature increasingly refers to "up to 55 degrees or the intended maximum flow/design temperature." This shows a growing recognition that there are sensible alternatives to the strict rules. The requirement is thus shifting from "maximum possible flow temperature" to "intended maximum flow temperature."

KlaRa schrieb:

The purpose is, on one hand, to determine (during functional heating) whether all components in the installed heating system are working properly.

With heat pumps, unfortunately, this is rarely the case.
Many heating professionals do functional heating using hot water heaters and similar equipment.
The heat pump, as an important part of the heating system, comes into play later.
Therefore, in practice, functional heating usually focuses more on the screed than the entire system.

KlaRa schrieb:

This means: when laying the floor covering, the screed does not have the necessary dryness throughout its cross section.

In our case, measurements are taken between the heating loops.
Due to the central drilling, the distance is at its maximum.
Whether the screed was dried to a readiness temperature of 35°C (95°F) or 60°C (140°F) makes no difference here.
Dry is dry, and damp is damp. This can be measured.

KlaRa schrieb:

I hope I was able to explain this understandably.

For me, this mixes functional heating and drying for floor covering readiness too much.
And there are no specific numbers.
The standards and information online vary widely between maximum flow temperature and 65°C (149°F).
So far, I have not seen a reasonable explanation as to why functional heating should significantly exceed the maximum design temperature.

Benutzer200 schrieb:

There are two answers to your question:
1 (formally correct): Heating up to 60°C (140°F) is necessary because only then does the warranty apply.
2 (practical/reasonable): Heating up to 60°C (140°F) is nonsense for a radiant floor system designed for a maximum of 30-35°C (86-95°F).

Thank you for clarifying that again.
The recommendation is to talk to the screed installer and explain this to them.
But that does not seem to be so easy. 😉

@KlaRa and @RotorMotor
To add: The P7 protocol for the acceptance heating of screed (Federal Association for Surface Heating and Cooling Systems) already includes that it is not necessary to heat at full capacity the entire time, but only up to the maximum design flow temperature. Not up to the maximum possible temperature.
For functional heating itself, only the maximum design temperature applies – for the heat pump, this is 30–35°C (86–95°F).