ᐅ Underfloor heating and heat pumps. I thought I had it all figured out.
Created on: 10 Nov 2021 19:52
S
Stefan001
Since October, we have been living in a KFW 55 house with an air-to-water heat pump and underfloor heating.
I have read through various sources about settings, hydraulic balancing, thermal balancing, and possibly lower heating curves... I thought I understood it.
Everything was fine to some extent: ERRs were switched off, the pump turned on 5-10 times a day, all rooms were consistently heated to their set temperatures, although the living room, where the temperature sensor is located, was constantly a bit too warm (23-24°C (73-75°F) instead of the target 21°C (70°F)). But now I wanted to focus on the hydraulic balancing.
The energy consultant came by after the heating installer and set the calculated hydraulic balance, reducing the flow rates from about 2 L/min (0.53 gal/min) to less than 1, more like 0.2-0.6 L/min (0.05-0.16 gal/min).
Most rooms are now cooler than before, the living room is at 22.5°C (72.5°F) but still warmer than the setpoint.
Now to my questions/understanding issues.
1.
The energy consultant said that an important factor is a maximum temperature difference between the flow and return pipes, and overall a low heating curve.
With the reduced volume flow, the flow speed should decrease, so the water stays longer in the heating circuit and thus releases more heat, increasing the temperature difference. But especially during the transition period, my flow temperature is already very close to the heating circuit temperature anyway, so the only way to create a temperature difference is by sharply raising the heating curve, and then the pump starts short cycling?!
2.
I have checked the flow and return temperatures several times, and today (7 PM), I noticed that the flow temperature is 22.7°C (73°F), the return temperature is 22.9°C (73.2°F), and the room temperature is 22.5°C (72.5°F).
How is it possible for the return temperature to be higher than the flow temperature? Basically, in most cases, I can hardly detect any temperature difference between flow and return.
3.
If the reference room is still getting warmer than the set temperature, what should I change? I thought about lowering the heating curve or reducing the flow rate. Which would be preferable? Lower the heating curve if most rooms are too warm, otherwise adjust the flow rate?
4.
What should I do if I cannot lower the heating curve any further? Currently, I have the base point at 20°C (68°F) and a slope of 0.25, which still results in relatively warm temperatures. I cannot lower the base point any further. The slope doesn’t seem to have much effect at the current outdoor temperatures. At what point does the base point intervene?
5.
What else should I keep in mind when adjusting the heating system? I can’t really interpret the flow and return values. How should they relate to each other and to the room temperature at this time?
Thank you very much for your help!
I have read through various sources about settings, hydraulic balancing, thermal balancing, and possibly lower heating curves... I thought I understood it.
Everything was fine to some extent: ERRs were switched off, the pump turned on 5-10 times a day, all rooms were consistently heated to their set temperatures, although the living room, where the temperature sensor is located, was constantly a bit too warm (23-24°C (73-75°F) instead of the target 21°C (70°F)). But now I wanted to focus on the hydraulic balancing.
The energy consultant came by after the heating installer and set the calculated hydraulic balance, reducing the flow rates from about 2 L/min (0.53 gal/min) to less than 1, more like 0.2-0.6 L/min (0.05-0.16 gal/min).
Most rooms are now cooler than before, the living room is at 22.5°C (72.5°F) but still warmer than the setpoint.
Now to my questions/understanding issues.
1.
The energy consultant said that an important factor is a maximum temperature difference between the flow and return pipes, and overall a low heating curve.
With the reduced volume flow, the flow speed should decrease, so the water stays longer in the heating circuit and thus releases more heat, increasing the temperature difference. But especially during the transition period, my flow temperature is already very close to the heating circuit temperature anyway, so the only way to create a temperature difference is by sharply raising the heating curve, and then the pump starts short cycling?!
2.
I have checked the flow and return temperatures several times, and today (7 PM), I noticed that the flow temperature is 22.7°C (73°F), the return temperature is 22.9°C (73.2°F), and the room temperature is 22.5°C (72.5°F).
How is it possible for the return temperature to be higher than the flow temperature? Basically, in most cases, I can hardly detect any temperature difference between flow and return.
3.
If the reference room is still getting warmer than the set temperature, what should I change? I thought about lowering the heating curve or reducing the flow rate. Which would be preferable? Lower the heating curve if most rooms are too warm, otherwise adjust the flow rate?
4.
What should I do if I cannot lower the heating curve any further? Currently, I have the base point at 20°C (68°F) and a slope of 0.25, which still results in relatively warm temperatures. I cannot lower the base point any further. The slope doesn’t seem to have much effect at the current outdoor temperatures. At what point does the base point intervene?
5.
What else should I keep in mind when adjusting the heating system? I can’t really interpret the flow and return values. How should they relate to each other and to the room temperature at this time?
Thank you very much for your help!
driver55 schrieb:
And where is the big rest? “2x the half” is still missing. (I’m not the thread starter) What information are you looking for? (You said “only the relevant details”). What do you consider to be the big rest of the missing information? (Or is there a checklist somewhere that can be followed?)
As I said, I’m not the original poster and every time I look into heating topics, my head starts to spin, because usually from page 2 onwards it’s all gibberish to me. (I still read them, hoping that by the time it becomes relevant to me, the chaos in my head will be a bit more organized.) My feeling is, I just don’t know what you want to know (I might have a few ideas, but then you might say “irrelevant”), but maybe the OP feels the same. The point is, I would probably struggle to give a satisfactory answer to a vague “just give us some info now.” :s (That might work if experts are discussing on the same level, but among non-experts it’s almost always difficult.)
Even after 4 years, I still haven’t fully understood everything about underfloor heating and heat pumps :-D
It should get warm, but you’re supposed to keep the heating curve low, and not throttle the rooms too much, yet if you don’t throttle enough, it gets too warm. Lowering the heating curve makes it okay there, but then another room is too cold, etc. :-D Vicious circle
It should get warm, but you’re supposed to keep the heating curve low, and not throttle the rooms too much, yet if you don’t throttle enough, it gets too warm. Lowering the heating curve makes it okay there, but then another room is too cold, etc. :-D Vicious circle
KingJulien12 Nov 2021 13:15Malz1902 schrieb:
Vicious circleNo, it’s a slow approach toward the optimum with ever smaller steps, followed by blissful satisfaction 😉mayglow schrieb:
(I’m not the OP) What information do you need? Well, the title is “I thought I understood it.”
If that were the case, he would also know which data is needed to perform an evaluation of the system/underfloor heating.
Design temperature / Number of heating circuits (rooms) / Length / Flow rates / Heating curve / Target room temperature / Cycling / Temperature differential / …
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