ᐅ Underfloor heating and heat pumps. I thought I had it all figured out.
Created on: 10 Nov 2021 19:52
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Stefan001S
Stefan00110 Nov 2021 19:52Since 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!
B
Benutzer20010 Nov 2021 22:34Stefan001 schrieb:
Everything was fine within certain limits, ERRs turned off, the pump switched on 5-10 times a day, With the current weather, that is about 2-7 times too often.
Stefan001 schrieb:
The energy consultant said that a wide temperature difference between supply and return is important. For which temperatures was the heating system designed? A typical example would be 30°C/26°C (86°F/79°F), meaning a maximum supply temperature of 30°C and a 4°C (7°F) difference.
Is the energy consultant aware that it requires more energy to repeatedly heat from a low temperature up to a high temperature? A car driving constantly at 80 km/h (50 mph) is also more energy efficient than frequently accelerating from 60 km/h to 100 km/h (37 mph to 62 mph).
I will provide more comments tomorrow. It’s too late for me today...
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RotorMotor11 Nov 2021 07:42Throttling everything is not ideal. It’s better to reduce the pump speed. Or is that not possible with the heat pump?
Which model is it, by the way?
How large is the house?
Is a bypass valve installed?
Which model is it, by the way?
How large is the house?
Is a bypass valve installed?
Stefan001 schrieb:
The supply temperature is 22.7°C (73°F), the return temperature is 22.9°C (73°F), and the room temperature is 22.5°C (72°F).
How is it possible that the return temperature is higher than the supply temperature? In most cases, I have hardly noticed any difference between return and supply temperatures.Could the supply sensor possibly be installed incorrectly?
KingJulien11 Nov 2021 09:19konibar schrieb:
Could the supply sensor be installed incorrectly?More likely: was there any heating cycle running at all?The 0.2°C (0.36°F) deviation is simply due to the inaccuracy of the sensors, or also just the installation location.
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