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
C
chewbacca123
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.
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.
Ötzi Ötztaler3 Oct 2020 15:59
Bookstar schrieb:
So, are you really heating already? Our heating was only on for about 4 hours in one week...Bookstar schrieb:
I might have one possible explanation after looking at the consumption over the last 7 days:
Heat energy for hot water: 35 kWh
Heat energy for heating: 61 kWh 61 kWh during "only 4 hours" with a modulating 9 kW pump, plus regularly stoking the wood stove, and my wife keeps the heating element glowing in the bathroom...
I think you’ll be a prime customer for heated blanket sellers on the senior trip.
D
Daniel-Sp3 Oct 2020 16:41How cold does it get where you are?
Your heat pump can only modulate down to 5.4 kW at an outdoor temperature of 7°C (45°F) with a flow temperature of 35°C (95°F). At even lower flow temperatures, the minimum capacity is actually higher. I’m afraid the heat pump is oversized by two sizes. The LAV 8 model would have been a better choice; it can modulate down to 2.8 kW at 7°C (45°F) outdoor temperature with a 35°C (95°F) flow temperature. Even that size might be too large if internal heat gains are taken into account.
The high output at the lowest modulation level also explains the short run times per heating cycle you mentioned somewhere here in the forum.
Your heat pump can only modulate down to 5.4 kW at an outdoor temperature of 7°C (45°F) with a flow temperature of 35°C (95°F). At even lower flow temperatures, the minimum capacity is actually higher. I’m afraid the heat pump is oversized by two sizes. The LAV 8 model would have been a better choice; it can modulate down to 2.8 kW at 7°C (45°F) outdoor temperature with a 35°C (95°F) flow temperature. Even that size might be too large if internal heat gains are taken into account.
The high output at the lowest modulation level also explains the short run times per heating cycle you mentioned somewhere here in the forum.
Ötzi Ötztaler3 Oct 2020 16:41
Bookstar schrieb:
But thanks for your very constructive contribution You're welcome.
Joking aside: Yes, domestic hot water has a poor COP, which significantly lowers the overall efficiency. Options include setting the hot water temperature to 45 to 48°C (113 to 118°F) with a higher hysteresis, or, if the storage tank is large enough, only enabling hot water heating in the early afternoon.
D
Daniel-Sp3 Oct 2020 17:07Is it still possible to optimize much if the heat pump is far too large? He does say that he has already optimized it.
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