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.
chewbacca1237 Dec 2019 20:59Lumpi_LE schrieb:
4000 is more like a 10-year target, depending on whether it’s a modulating pump or not. Oops, okay, well, great. What causes that? Why such a frequency?
D
Daniel-Sp7 Dec 2019 23:38The energy saving regulation requires ERR for heated rooms. Since heat pump manufacturers assume they will be used (meaning several heating circuits are closed), but the heat pump needs a minimum flow rate, installation schemes include measures such as bypass valves and buffer tanks. The heating installer follows these manufacturer-approved hydraulic diagrams to always be able to claim that the system was built according to the manufacturer's requirements in case of problems.
What happens: Due to the ERR, heating circuits are closed, the minimum flow rate is undershot, and the pressure increases, causing the bypass valve to open and warm supply flow to go directly into the buffer on the return side. The buffer can only store a minimal amount of heat, so the return temperature rises quickly. Your heat pump is controlled by the return temperature. After a short time, the target return temperature plus hysteresis is reached, and the compressor switches off. On average, this takes about 14 minutes in your system. The compressor stops, but the heating circulation pump continues to run as intended, the supply temperature drops, and so does the return temperature. Since the screed in the open circuits is still cold, the measured return temperature falls below the lower hysteresis band after a short time, and the compressor starts again, repeating the short cycling caused by the bypass valve. If your heat pump were not also producing domestic hot water, the average compressor run times would probably be even shorter. To ensure some heat reaches the rooms during these short run periods, the heating curve is set much too high, which only worsens the problem.
I assume your heating installer follows the manufacturer's installation instructions and will not uninstall the ERR on Monday (or set it to maximum) or completely close the bypass valve. You will have to deal with your heating system yourself.
You do not have a bad heat pump; it is simply operated incorrectly.
We have lived in our house since August and have just reached 210 compressor starts. Also a Novelan heat pump...
Best regards, Daniel
What happens: Due to the ERR, heating circuits are closed, the minimum flow rate is undershot, and the pressure increases, causing the bypass valve to open and warm supply flow to go directly into the buffer on the return side. The buffer can only store a minimal amount of heat, so the return temperature rises quickly. Your heat pump is controlled by the return temperature. After a short time, the target return temperature plus hysteresis is reached, and the compressor switches off. On average, this takes about 14 minutes in your system. The compressor stops, but the heating circulation pump continues to run as intended, the supply temperature drops, and so does the return temperature. Since the screed in the open circuits is still cold, the measured return temperature falls below the lower hysteresis band after a short time, and the compressor starts again, repeating the short cycling caused by the bypass valve. If your heat pump were not also producing domestic hot water, the average compressor run times would probably be even shorter. To ensure some heat reaches the rooms during these short run periods, the heating curve is set much too high, which only worsens the problem.
I assume your heating installer follows the manufacturer's installation instructions and will not uninstall the ERR on Monday (or set it to maximum) or completely close the bypass valve. You will have to deal with your heating system yourself.
You do not have a bad heat pump; it is simply operated incorrectly.
We have lived in our house since August and have just reached 210 compressor starts. Also a Novelan heat pump...
Best regards, Daniel
chewbacca1238 Dec 2019 09:23Daniel-Sp schrieb:
The energy saving regulation requires ERR for heated rooms. Since heat pump manufacturers assume the system will be used (meaning multiple heating circuits are closed), and the heat pump requires a minimum flow rate, installation diagrams include measures such as bypass valves and buffer tanks. The heating technician follows these manufacturer-approved hydraulic schematics to be able to say, in case of problems, that the system was built as specified by the manufacturer.
What happens: Due to the ERR, heating circuits close, the minimum flow rate is not met, and pressure rises, causing the bypass valve to open. Warm supply water then flows directly into the buffer tank on the return side. The buffer can store only a small amount of heat, so the return temperature rises quickly. Your heat pump is controlled by the return temperature. After a short time, the set return temperature plus hysteresis is reached and the compressor switches off. In your case, this happens on average after 14 minutes. The compressor stops while the heating circulation pump continues to run as intended, the supply temperature drops, and so does the return temperature. Since the screed in the open circuits is still cold, the measured return temperature falls below the lower hysteresis band shortly after, and the compressor restarts, causing the same short-circuit cycle via the bypass valve to repeat. If your heat pump did not produce domestic hot water, the average compressor run times might be even shorter. To ensure some heat reaches the rooms in these short cycles, the heating curve is set much too high, which only worsens the problem.
I assume your heating installer is following the manufacturer’s installation instructions and will not uninstall the ERR on Monday (or set it to maximum) or fully close the bypass valve. You will have to deal with your heating system yourself.
You don’t have a bad heat pump; it’s just operated incorrectly.
We have lived in our house since August and have had about 210 compressor starts so far. Also a Novelan heat pump...
Best regards, DanielFirst of all, many thanks for your detailed response; it helps me understand the situation better. Unfortunately, I am a complete beginner in this field. I have now made some adjustments as you suggested. However, I couldn’t change the hot water hysteresis to 6; I have no option for that, it remains at 2. The heating curve is now set to 28-22-0, and the hot water temperature is 48°C (118°F).
Supply and return temperatures, see attached images, look much better now; they are no longer the same. I made these settings yesterday afternoon, but this morning some rooms are quite cool—for example, the living room is only 20.5°C (69°F), although the thermostat is set to 22-23°C (72-73°F). We also want it cozy in the bathroom, which is usually around 23-24°C (73-75°F), but now it’s also only 20.5°C (69°F). We have a small baby at home, so it’s quite cold, especially in the bathroom, where it should be warmer.
How can this be explained? I included some pictures for reference. Our installer will come by tomorrow afternoon, and I plan to discuss this entire issue with him. But don’t many people face this problem with such heating systems? It’s quite complex, and right now I only have the time to focus on it because I’m on parental leave.
Or is it simply because our installer didn’t set up the system properly at all?
D
Daniel-Sp8 Dec 2019 09:54Hello,
The password to change the DHW hysteresis is 9445. If it’s too cold, increase the heating curve to 30/22/0.
Since you mentioned that the TRV (thermostatic radiator valve) is set to 22–23 degrees, I assume not all TRVs are set to the maximum. What total flow do your flow meters on the heating circuit distributor show? And the all-important question: Is the bypass valve fully closed? I suspect it’s not.
You should use today to read the heat pump controller’s user manual, including the one for professionals (you can find it on the homepage). Tomorrow, have someone show you the bypass valve and explain how to operate the flow meters on the heating circuit distributor (fully open; ask if there are additional flow restrictors on the supply and return).
Which model was installed?
Yes, the control system is complicated. Most people only notice problems after a few years, when the heat pump fails. The technician follows the manufacturer’s instructions.
You have to take care of it yourself.
If the heat pump no longer cycles and the heating curve is roughly correct, the hydraulic balancing comes next—but not via the TRVs, rather via the flow meters. If everything is set correctly, you shouldn’t need to adjust the heating system anymore.
Also important are the lengths of the individual heating circuits!
Regards, Daniel
The password to change the DHW hysteresis is 9445. If it’s too cold, increase the heating curve to 30/22/0.
Since you mentioned that the TRV (thermostatic radiator valve) is set to 22–23 degrees, I assume not all TRVs are set to the maximum. What total flow do your flow meters on the heating circuit distributor show? And the all-important question: Is the bypass valve fully closed? I suspect it’s not.
You should use today to read the heat pump controller’s user manual, including the one for professionals (you can find it on the homepage). Tomorrow, have someone show you the bypass valve and explain how to operate the flow meters on the heating circuit distributor (fully open; ask if there are additional flow restrictors on the supply and return).
Which model was installed?
Yes, the control system is complicated. Most people only notice problems after a few years, when the heat pump fails. The technician follows the manufacturer’s instructions.
You have to take care of it yourself.
If the heat pump no longer cycles and the heating curve is roughly correct, the hydraulic balancing comes next—but not via the TRVs, rather via the flow meters. If everything is set correctly, you shouldn’t need to adjust the heating system anymore.
Also important are the lengths of the individual heating circuits!
Regards, Daniel
chewbacca1238 Dec 2019 10:18Daniel-Sp schrieb:
Hello,
The password to change the DHW hysteresis is 9445. If it is too cold, increase the heating curve to 30/22/0.
Since you mentioned that the ERR is set to 22–23 degrees, I assume not all ERRs are set to the maximum. What total flow rate do your flow meters at the heating circuit manifold show? And the all-important question is: Is the bypass valve completely closed? I suspect not.
You should use today to read the heat pump controller’s manual, including the professional installation instructions (available on the website). Tomorrow, have the bypass valve shown to you and explained, along with how to operate the top meters at the heating circuit manifold (fully open them, and ask about any additional flow restrictors on the supply and return lines).
Which model was installed?
Yes, the control system is complicated. Most people only become aware of the problems after a few years, when the heat pump breaks down. The technician follows the manufacturer’s guidelines.
You have to take care of it yourself.
If the heat pump is no longer cycling and the heating curve is roughly correct, then the hydraulic balancing will be done—not via the ERRs but through the top meters. When everything is correct, you won’t need to adjust the heating anymore.
Also important are the lengths of the individual heating circuits!
Regards, Daniel Silly question – if I set all ERRs to full power, won’t it get quite hot everywhere? Especially in the bedroom, where we actually prefer to have no heating on at all.
The bypass valve is not closed, because I don’t even know where it is. I will definitely have it shown to me tomorrow since I don’t know where it is. I will definitely have it shown to me tomorrow.
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