ᐅ Underfloor heating not working properly or too slow to respond?

Hi, we feel like our underfloor heating is not working properly.

We have a newly built house, moved in earlier this year, KFW 55 standard.
With an air-to-water heat pump.

When we moved in at the beginning of March this year, the floor was always nice and comfortably warm. So, you could definitely feel the underfloor heating.
Now, you hardly notice it anymore.
Of course, the floor is not ice cold, but it’s also not as warm as it was at the beginning.
Room temperatures are around 21°C (70°F).

Our current problem:
We were on vacation from December 12th until today, December 21st.
I set the heat pump to vacation mode from December 13th to December 20th with a setback of about -4°C (25°F).
Now we came home this evening, and it’s freezing inside.
Downstairs it’s 18°C (64°F) and upstairs in the kids’ rooms only 15°C (59°F).

Is the underfloor heating really that slow to respond? I thought it would only take a few hours to warm up.
It’s now been running normally again for over 24 hours.
Why is it still so cold?

Strange, 12 hours are more than enough for us.

What is the outdoor temperature where you are right now?
There are outdoor temperatures at which the heating system doesn’t turn on. It’s too warm for it to start running properly.
Especially in autumn, the weather alone is enough to keep the system satisfied.
For us, it feels cold, though.
I have a small dial on the gas heater; I turn it up three times and then it starts running. Don’t ask me whether that setting controls the temperature or the heating curve.

Basically: With a properly sized heat pump, it is normal for it to take a long time to reheat a house. In my case, it takes more than a day. A noticeably warm floor would be a sign of an inefficiently running heat pump.

I suspect the heating system does not recognize that there is a significantly higher heating demand because it controls the flow temperature based on the outside temperature, which is currently quite warm. That is why reheating takes so long. If the heat pump is not already running at full capacity, you can temporarily increase the flow temperature manually to speed up the process.

305er schrieb:
I set the heat pump to holiday mode from December 13 to December 20 with a temperature reduction to, I believe, -4 degrees.

Stop with that nonsense. You have a heat pump. If you reduce the temperature for your holiday, do it like this:

December 13 to December 18, if you are coming back on December 21.

Especially when the temperatures are like now, around 10°C (50°F).

At the current temperatures, you will indeed have a problem warming the house again. Lowering the temperature in KfW 55 houses with an air-to-water heat pump should be avoided. Additionally, the floor in such a house should only warm up at around -20°C (-4°F); otherwise, something is wrong.