ᐅ Underfloor heating with an air-to-water heat pump. House gets too warm when the sun is shining.

Created on: 4 Dec 2019 14:18

Hello everyone,

I have a general question.

We moved into our new build four months ago. The living area on the ground floor has three large floor-to-ceiling windows facing south. We have underfloor heating and an air-to-water heat pump.
It provides a really comfortable temperature inside the house, but we have a problem – whenever the sun is shining in winter, even if it’s -2°C (28°F) outside, the temperature suddenly rises to 24°C (75°F) in the living room. It gets uncomfortably warm in here, and the underfloor heating can’t be turned down quickly.
Should we assume that the large floor-to-ceiling windows are responsible for the heat gain? A photo of the south-facing side of the house is attached.
What would you do – always lower all the blinds as soon as sunlight is forecast? That seems quite annoying...
We have motorized blinds controlled by Somfy. Would you consider buying a sensor that automatically lowers the blinds at a certain temperature?

Thanks in advance for your replies.

Neues zweistöckiges Haus auf Baustelle mit weißer Blockfassade, pinker Dämmung und großen Fenstern

Daniel-Sp21 Dec 2019 14:06

#253

The question is whether you get more flow through the underfloor heating if you slowly (gradually) close the bypass valve?
You still have 26 compressor starts in 48 hours. I have 3 per day.

chewbacca12321 Dec 2019 15:53

#254

Daniel-Sp schrieb:

The question is whether you get more flow through the underfloor heating if you gradually close the bypass valve step by step?
You still have 26 compressor starts within 48 hours. I have 3 per day.

Can nothing happen if you close the valve gradually? In other words, is there no risk of damage if pressure builds up that cannot be released?

Daniel-Sp21 Dec 2019 17:00

#255

Then the heat pump shows an error message and shuts down. You can then reopen the bypass valve and reset the error.
Therefore, close it gradually while the pump is heating; you just need to be careful or briefly raise the heating curve to trigger a heating cycle.

Daniel-Sp21 Dec 2019 17:06

#256

chewbacca123 schrieb:

Could it also be because I only have a flow rate of 1059 l/h instead of the 1600 that the LAD 9 requires?
Exactly, the bathroom radiator runs on electricity, independent of the air-to-water heat pump.

This happens because hot water reaches the return line too quickly. However, this does not occur with water flowing through the underfloor heating circuits, but with water bypassing these circuits. In your case, this is through the bypass valve. This is independent of how powerful the heat pump is.

Daniel-Sp21 Dec 2019 20:07

#257

chewbacca123 schrieb:

Where can I find the heating load for our house?

For an estimate, you need
Ht, building envelope surface area, heated gross volume, desired indoor temperatures, standard outdoor temperature, and number of occupants.
You can find these, for example, in the KFW certificate.
With this information, you can get a reliable estimate.

chewbacca12321 Dec 2019 20:27

#258

Daniel-Sp schrieb:
To estimate, you need Ht, envelope surface area, heated gross volume, desired temperatures, standard outdoor temperature, and number of occupants. You can find these, for example, in the KfW certification. This will give you a good approximation.

We did not build a KfW house.

ᐅ Underfloor heating with an air-to-water heat pump. House gets too warm when the sun is shining.

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