Is the attic always colder than the ground floor?

Our heating technician also pointed out that the pump must be set to a certain minimum performance in order to achieve the delivery height to the upper floor. When you adjust the performance on our pump, a display in meters also briefly appears.

Hello Musketier,

that will not be correct either. As mentioned, the delivery height does not matter in a closed circuit. It is standard and common practice with pumps that the specification of the possible differential pressure is always given in meters, so to speak as delivery height. If a cooling circuit has a pressure loss of 2 bar (flow losses), a pump with at least 20m "delivery height" is used. Even in plant engineering, the mistake is sometimes made to additionally take into account the actual delivery height. It becomes criminal when the pump is mounted "at the top," and the "delivery height" is subtracted.

That could quite well be the case. I'm not very familiar with the subject. I could probably test it relatively easily by turning down the pump's power further and observing the temperature development on the upper floor.

I've also set my heating's flow rate and temperature curve about a year ago so that except for the guest room and bedroom, no ERRs are in operation, and still, the desired temperatures prevail in the rooms both summer and winter.

During the heating maintenance, the guy initially looked a bit strange when I told him that I had changed the flow rates and thus "destroyed" the hydraulic balancing, but on the other hand, he was more than satisfied with the low flow temperature.

The maintenance technicians were always puzzled for the first few years with me... but by now they know the house.

If we open all the thermostats completely, we also have a temperature difference between the ground floor and the top floor. This is logically understandable to me, since in the top floor you still have the roof as an "outer wall." Additionally, the water in the supply line might still cool down a bit due to the longer distance from the basement to the top floor, despite insulation.

How high is this difference? Well, that could also be the reason in our case... the pipes are not insulated yet....

How big is this difference? Well, that could still be the reason for us... the pipes are not insulated yet....

You can measure how big the temperature difference is between the beginning and the end. I guess at most 0.1 Kelvin. Of course, your upper floor then becomes noticeably 0.05 Kelvin colder. Didn't you have physics class?

That's exactly what I already said. It's simply logical, and on top of that a 1-degree difference...

Increase the flow temperature until it fits upstairs, and adjust accordingly downstairs. Problem solved.

It is not 1 degree (I wouldn't worry about that), but a good 2 degrees.

The flow temperature is set to a maximum of 35 degrees at -20 degrees outside temperature. Of course, I can adjust that... but again... the adjustment doesn't change the 2-degree difference to the upper floor. It gets warmer (3 degrees more flow temperature = 0.3 - 0.5 degrees room temperature), but the difference remains.

The flow in the upper floor is fully open on all valves. Just checked. The pump should be strong enough. It ran at maximum power (level 6) in the weeks before. For some time now on level 1. This has had no noticeable effect on the temperature.

The manufacturer's heating service said that maybe the heating should be vented/flushed because air bubbles might be in the pipes due to the installation. But the installer refuses and claims that this is impossible, because otherwise we would have no flow on the ground floor.

We have received no documents from the general contractor or the heating technician about the installation of the underfloor heating. The hydraulic balancing on paper, yes. But I cannot say what the layout plan of the heating coils looks like. Should we get that? The coils were laid very tightly... surprisingly, where they were laid less tightly (hallway, for example), it is also nicely warm. That was actually where we had our concerns. But not where they were laid tightly, like in the bathroom...