Underfloor heating warm despite being turned off - cold despite being turned on

Hello everyone,

I recently bought a house. After the purchase, I noticed something strange. Maybe one of you has an idea what could be the reason.

It is a house built in 1992, with underfloor heating on the ground floor (plus a small radiator in the bathroom) and conventional radiators on the upper floor. The gas boiler is from 2014. Until the beginning of the week, the heating was in hot water mode without heating. All underfloor heating circuits were turned off. Nevertheless, I had a floor temperature of 24°C in the study (north side, regular window), but only 14°C in the bedroom (south side, window + patio door) on the other side of the hallway. In the living room (south side, two patio doors, three windows), the temperature was around 19°C. Since the middle of the week, the heating is in heating + hot water mode. The heating circuit for the bedroom is slightly turned on. For the study still completely off. In the study, the floor temperature has risen to a cozy 27°C. In the bedroom only to 15°C.

The valves are controlled via the usual plastic caps, so nothing smart. The valve stems move freely as far as I could get the caps off. I cannot rule out that the labeling of the circuits is wrong. That would definitely be a possible explanation for the behavior after the heating was switched on.

But what I wonder is: how can such temperature differences occur with the heating off that become even more pronounced when the heating is switched on?

Best regards

Very strange and I can't make sense of it like this. Could it be that the hot water pipes run through the study? If they are not properly insulated, I can imagine that they could heat up the floor. 27 °C is quite something, the water temperature must really be high flowing through the floor for that to happen.

Is the heating circuit distributor on the upper floor in the study? Then the higher temperature might be explainable.

Are the valves controlled via ERR or directly on the radiator, or are you adjusting the heating circuit distributor?

I would basically turn off the bedroom and turn on the study. With radiators, you more or less have to notice the change immediately. We also swapped the rooms compared to the original building plan, so our heating circuits have different labels on them.

the heating circuit distributor and all underfloor heating circuits are on the ground floor.

At least I was able to solve one problem. In the rotary knob for the study, there was a hole exactly where the plunger is located. No matter how I turned it, it was always fully open. I have now cut off a cap from a water bottle and placed it inside so that the circuit is not always fully open. Does anyone know where I can get replacements for these manual controllers? They are all either very tight or completely worn out, and the plastic is broken.

Could it be that the heating circuits from the domestic hot water system (domestic hot water buffer?) also always receive a little heat? That would explain why the study was warmer during the hot water operation.

Does anyone know where I can get replacements for these manual controllers?

Unfortunately, I can no longer edit it. I wanted to add that I found nothing at Obi, Bauhaus, or Hornbach. And Google is currently only showing me thermostat heads for normal radiators or room temperature controllers.

Perhaps you should post a picture of the hand controller, maybe you can get some help with that.

By the way, I have no idea how the combination of a normal heating circuit and underfloor heating works, so I can only help you to a limited extent. In domestic hot water mode, I would simply follow the piping and see which pipes are warm.