ᐅ Cooling with a heat pump through underfloor heating?

drno1234 schrieb:

The limiting factor is the dew point.

That is exactly why the effect is even less pronounced the more humid the air is. Therefore, an air conditioning system is not only about cooling but also about dehumidifying. This should not be overlooked.

K1300S schrieb:

That’s exactly why the effect is less noticeable the more humid the air is. Therefore, an air conditioning system is not just about cooling but also about dehumidifying. That should not be overlooked.

Absolutely correct.

As I mentioned, it’s important for me to distinguish between opinions and real EXPERIENCES, since I have seen the argument "humidity stays the same anyway" several times in this thread.
Concrete experience in my house:
- without cooling function: about 28°C (82°F) at 60 percent relative humidity
- with air-to-water heat pump cooling function: about 24°C (75°F) at 72 percent relative humidity
The latter feels SIGNIFICANTLY more comfortable despite the higher relative humidity.

Experience in my parents’ house:
With an air conditioner it goes down to 24°C (75°F) or lower at 30 percent humidity. Much fresher, but over time (for some people) also less comfortable due to very dry air, a common complaint being "I get sick from air conditioning."

If both cost the same, I would choose the air conditioner. However, cooling 200 square meters with an air conditioner costs about five times as much as using the heat pump’s cooling function in my case.

So, my experiences with both (air conditioning + air-to-water heat pump cooling) are on the table. Everyone can now decide which is better for them individually.

In my opinion, the crucial answer is still missing here:

THERMAL CONVECTION

As is well known, cold air sinks and warm air rises.
No one would think of installing radiators on the ceiling.

Using cooling surfaces at the bottom makes little sense because you want to cool the warm air above.
Instead, you only end up with cold feet and a hot head.
To counter this, you would need to run at least a powerful fan.

Therefore, the answer to the original question is:
yes, but it works more poorly than effectively.

The poor cooling efficiency might be tolerable if this cooling is only used for a few days per year.

However, this solution is not very satisfying.

konibar schrieb:

No one would think of installing radiators on the ceiling.

Radiators no, but large-area heating and cooling ceiling systems are quite standard in high-end commercial buildings. These operate almost entirely through radiation rather than convection. So I don't think "No one" is entirely correct!

I agree with you about cooling. Ceiling installation is indeed ideal for that.

drno1234 schrieb:

below that, the pipes (which have to be significantly cooler than the target temperature) start to sweat.

Which pipes are you referring to here? The 50cm (20 inches) per heating circuit in the central heating manifold?
The others are not exposed, after all. 😕

In my case, it’s the cold water pipe in the boiler room that sweats when I fill our “paddling pool” over many minutes…

driver55 schrieb:

Which pipes are you referring to here? The 50cm (20 inches) per heating circuit at the hydraulic separator?
The others are not exposed. 😕

In my case, the cold water pipe in the boiler room sweats when I fill our "paddling pool" over several minutes…

A dew point sensor is installed on the supply line between the heat pump and the hydraulic separator. It measures the relative humidity directly on the pipe and disables the cooling function if a defined threshold is exceeded. Mine is set to 80%, since mold growth can occur at this level of relative humidity.
The threshold can be set higher, because the floor temperature will always be higher than that of the supply line—so high moisture on the pipe does not necessarily mean moisture will be present on the floor. Since this setup is more than sufficient for me, as explained above, I keep it at 80%.