ᐅ HvH combines an air-source heat pump with panel radiators – what about the temperature settings?
Created on: 17 Nov 2015 22:42 ölschlamm
Hello community,
I just had a conversation with my regional manager from Heinz von Heiden. The houses now typically use an air-source heat pump combined with conventional radiators operating at a flow temperature of 55°C (131°F).
Doesn't this basically mean a seasonal performance factor below 2 is inevitable?
From my intuitive assessment, I would say that a flow temperature of 40°C (104°F) is sufficient for almost all days of the year. But even that is still way too high for a heat pump.
What do you think?
I just had a conversation with my regional manager from Heinz von Heiden. The houses now typically use an air-source heat pump combined with conventional radiators operating at a flow temperature of 55°C (131°F).
Doesn't this basically mean a seasonal performance factor below 2 is inevitable?
From my intuitive assessment, I would say that a flow temperature of 40°C (104°F) is sufficient for almost all days of the year. But even that is still way too high for a heat pump.
What do you think?
Perhaps we are referring to different systems. The standard 22-profile double-panel radiators actually release most of their heat through air circulation—known as the chimney effect. It may be different with true flat panel radiators (single panel), but I am not sure. What is certain, however, is that the low supply temperature results in a higher proportion of radiant heat.
This means that the heating output from radiation increases disproportionately with temperature; it can be slightly influenced by material and color choices, but not completely overridden. Conversely, the radiant heat output decreases significantly as the temperature drops (and the frequency spectrum changes as well, which can be important—especially if the comfortable radiant warmth constitutes a smaller portion).
A radiator can only have a high radiant heat share at a low supply temperature if the convection output is ESPECIALLY low; in other words, the radiator overall has low heating capacity. However, in a well-insulated house, heating loads of around 300 watts for an average-sized room during bitter cold outside conditions can already be sufficient.
A radiator can only have a high radiant heat share at a low supply temperature if the convection output is ESPECIALLY low; in other words, the radiator overall has low heating capacity. However, in a well-insulated house, heating loads of around 300 watts for an average-sized room during bitter cold outside conditions can already be sufficient.
Saruss schrieb:
In the manual for the mentioned heat pump, you can find on page 23 after 5 seconds the important data: the COP is about 2–2.5 at 0 degrees source temperature and 55° flow temperature. According to my source, it is page 21. There, I read a COP of 2.75 at 0°C (32°F) and 50°C (122°F) flow temperature. If I operate at 45°C (113°F), the COP should still be around 2.5 even at −10°C (14°F).
Which source do you have? I have the 48-page manual as a PDF file.
It is strange that nowhere in my manual return temperatures are mentioned. That seems important — or does EN 14511 assume a standardized parameter?
Well, I simply got them from the manufacturer’s website, novelan.com. On page 23 of the 48-page manual, there are performance charts. However, the curves drop sharply as the supply temperature increases, so your figures are correct. But is a 45°C (113°F) supply temperature really enough for radiators at -10°C (14°F)? Additionally, the total output clearly decreases at those temperatures, so a heating element is needed quickly. The temperature difference in the values is 5 K (5°C, 9°F). Is that caused by the radiators, the circulation pump, or something else? The heat pump itself is quite good, but I see the problem that if it delivers enough power below 0°C (32°F), it will cycle a lot at 8-15°C (46-59°F), meaning it has too much capacity and may operate inefficiently.
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