ᐅ Underfloor heating warm even when turned off – cold even when turned on

Hello everyone,

I recently bought a house. After the purchase, I noticed something strange. Maybe someone here has an idea what could be causing it.

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 this week, the heating was in hot water operation only, without heating. All underfloor heating circuits were turned off. Still, in the study (north side, standard window) the floor temperature was 24°C (75°F), while in the bedroom (south side, window plus patio door) on the other side of the hallway it was only 14°C (57°F). In the living room (south side, two patio doors, three windows) the temperature was around 19°C (66°F).
Since midweek, the heating is operating in both heating and hot water mode. The heating circuit for the bedroom is slightly open. For the study, it is still completely off. The floor temperature in the study has risen to a cozy 27°C (81°F). In the bedroom, it only increased to 15°C (59°F).

The valves are controlled by the usual plastic caps, so nothing smart. The valve stems move freely as far as I could see after removing the caps.
I cannot rule out that the labeling of the circuits is incorrect. That would definitely be a possible explanation for the behavior after switching on the heating.

What I wonder is: how can such temperature differences occur when the heating function is turned off, and why do they increase so much when the heating is switched on?

Best regards

Very strange, and I can’t make much sense of it as it is. Could it be that the hot water pipes run through the study? If they are not properly insulated, I can imagine they could heat up the floor.
27°C (81°F) is quite a claim; there must be a significant water temperature running through the floor for that to happen.

Is the heating circuit manifold on the upper floor in the study? That might explain the higher temperature.

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

In principle, I would try turning off the heat in the bedroom and turning it on in the study. With radiators, you should notice the change more or less immediately.
We actually switched the rooms compared to the original building plan, so the labels on our heating circuits are different.

@Musketier The heating manifold and all underfloor heating loops are on the ground floor.

I was able to solve at least one problem. The rotary knob for the study had a hole exactly where the stem sits. No matter how much I turned it, it was always fully open. I have now cut out a cap from a water bottle and placed it inside so the loop isn’t always fully open.

Does anyone know where I can get replacements for these manual controllers? They are either stuck very tightly or completely worn out, and the plastic is damaged.

Is it possible that the heating loops from the domestic hot water system (domestic hot water buffer tank?) also receive some residual heat? That would explain why the study was warmer even during the domestic hot water operation.

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

Unfortunately, I can no longer edit the post. I wanted to add that I haven’t found anything at Obi, Bauhaus, or Hornbach. And Google is currently only showing me thermostat heads for standard radiators or room temperature controllers.

Maybe you should post a picture of the manual controller; that might help you get some assistance.

Otherwise, I have no idea how the combination of a regular 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 pipe routing and check which pipes are warm.