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

Joedreck11 Jan 2021 08:28

#631

Bookstar schrieb:

So, ours is completely escalating right now. At minus 8 degrees Celsius (17.6°F), we need 38 kWh of electricity daily. The system has automatically lowered the hot water temperature from 48 to 44 degrees Celsius (118°F to 111°F). It can’t manage any more at the outdoor temperature.

Sometimes I really long for the gas heating back, especially in winter 🙁

Something is still wrong with your system. If I remember correctly, the heat pump is even oversized.

Bookstar11 Jan 2021 08:36

#632

Joedreck schrieb:

Something is still off with your setup. If I remember correctly, the heat pump is even oversized.

According to the heating load calculation, it’s not, but those calculations are always quite conservative. It’s definitely too large. It’s just strange that it can’t handle the domestic hot water anymore. Is no one else here having this problem?

chewbacca12311 Jan 2021 08:54

#633

So far, we haven’t had this problem. The outside temperature is currently -7°C (19°F).
I need to check the consumption; at the moment, everything is connected to a single meter, so I have to figure out how to calculate it.
I’m really happy with the photovoltaic system! When it’s sunny, we basically heat for free.

Alessandro11 Jan 2021 08:57

#634

but not in winter 😉

Joedreck11 Jan 2021 09:00

#635

Bookstar schrieb:

According to the heating load calculation, no, but that calculation is always on the safe side. It is definitely oversized by one step. Strange though, why it then can’t handle the domestic hot water anymore. Does nobody else here have this problem?

Is there enough time to prepare the domestic hot water? Including the defrosting process, possibly?

face2611 Jan 2021 09:08

#636

Bookstar schrieb:

According to the heating load calculation, no, but that calculation always errs on the safe side. It’s definitely oversized. It’s just strange that it can no longer handle the domestic hot water. Does no one else here have this problem?

Maybe the maximum heating output for domestic hot water is limited?
I’m not familiar with your model. In ours (modulating), the maximum heating capacity is limited to 80% for heating mode and 70% for domestic hot water according to factory settings. I only discovered this a few days ago when I was looking into it on a technical level.
At outdoor temperatures around -8°C (17.6°F), the pump probably needs to run at full speed to nearly reach the required kW output...

No idea, just a thought...

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

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