Just out of curiosity, to better understand the slope of the heating curve, what flow temperatures do you typically run at 0°C (32°F) outdoor temperature, given a certain indoor temperature and insulation level, when using a combination of underfloor heating and a heat pump?
Background of the question:
My logic tells me that if I want, for example, 22°C (72°F) room temperature, the flow temperature must be at least 22°C (72°F) or higher, since I learned that there needs to be a temperature difference for heat transfer to occur.
So if my heating system turns on at 12°C (54°F) outdoor temperature, my flow temperature should logically start somewhere around 22°C–25°C (72°F–77°F). Accordingly, at only 5°C (41°F) outside, it should be around 27°C (81°F), and at 0°C (32°F) close to 30°C (86°F).
The system design usually takes the location and outdoor temperature down to about –12°C (10°F). If at 0°C (32°F) flow temperature is already 30°C (86°F) according to my logic, then at –12°C (10°F) the flow temperature should be about 40°C (104°F). But most underfloor heating designs for heat pumps are based on a maximum flow temperature of 35°C (95°F).
Of course, the insulation of the house and the indoor temperatures still play a role. Or is the increase in flow temperature actually so gradual that it only rises by about 0.5–1°C (1–2°F) for outdoor temperature drops in 0–5°C (0–9°F) increments?
Background of the question:
My logic tells me that if I want, for example, 22°C (72°F) room temperature, the flow temperature must be at least 22°C (72°F) or higher, since I learned that there needs to be a temperature difference for heat transfer to occur.
So if my heating system turns on at 12°C (54°F) outdoor temperature, my flow temperature should logically start somewhere around 22°C–25°C (72°F–77°F). Accordingly, at only 5°C (41°F) outside, it should be around 27°C (81°F), and at 0°C (32°F) close to 30°C (86°F).
The system design usually takes the location and outdoor temperature down to about –12°C (10°F). If at 0°C (32°F) flow temperature is already 30°C (86°F) according to my logic, then at –12°C (10°F) the flow temperature should be about 40°C (104°F). But most underfloor heating designs for heat pumps are based on a maximum flow temperature of 35°C (95°F).
Of course, the insulation of the house and the indoor temperatures still play a role. Or is the increase in flow temperature actually so gradual that it only rises by about 0.5–1°C (1–2°F) for outdoor temperature drops in 0–5°C (0–9°F) increments?
Here are the temperatures after the heating ran overnight.
Outdoor temperature just now ~9°C (48°F)
Guest room 21.3°C (70°F)
Occupied overnight.
Bathroom 20°C (68°F)
Bedroom 20.3°C (69°F)
Window tilted open overnight because it was too warm or else it would have been even warmer.
Hallway 21.3°C (70°F)
Living/Dining/Kitchen 21.2°C (70°F)
Window tilted open for initial ventilation
WC 20.3°C (69°F)
Window tilted open for initial ventilation
Utility room 20-22°C (68-72°F)
Window tilted open overnight because it would otherwise be too warm or even warmer.
Outdoor temperature approx. 9°C (48°F), heating curve as usual 0.1, target temperature 20°C (68°F)
Flow rate as usual about 750 liters/hour (198 gallons/hour)
Heat pump controller requested a supply temperature setpoint of 22.5°C (73°F) at these outdoor temperatures and heating curve.
Temperature-wise, everything feels fine. The bathroom might benefit from a bit more flow. Then the guest room, bedroom, hallway, WC, and utility room could have a little less. Or I would probably prefer to completely turn off the utility room via the room thermostat since it is already too warm due to external heat (and I would like to direct the flow more toward the bathroom).
I’m just not sure whether it makes sense to adjust anything now again, or if I should wait until it stays around 5°C (41°F) 24/7 and the heating runs longer. Also, I’m curious about how the cycling behavior will develop—short loops like WC and hallway could act like a shortcut and cause the system to cycle frequently.
Outdoor temperature just now ~9°C (48°F)
Guest room 21.3°C (70°F)
Occupied overnight.
Bathroom 20°C (68°F)
Bedroom 20.3°C (69°F)
Window tilted open overnight because it was too warm or else it would have been even warmer.
Hallway 21.3°C (70°F)
Living/Dining/Kitchen 21.2°C (70°F)
Window tilted open for initial ventilation
WC 20.3°C (69°F)
Window tilted open for initial ventilation
Utility room 20-22°C (68-72°F)
Window tilted open overnight because it would otherwise be too warm or even warmer.
Outdoor temperature approx. 9°C (48°F), heating curve as usual 0.1, target temperature 20°C (68°F)
Flow rate as usual about 750 liters/hour (198 gallons/hour)
Heat pump controller requested a supply temperature setpoint of 22.5°C (73°F) at these outdoor temperatures and heating curve.
Temperature-wise, everything feels fine. The bathroom might benefit from a bit more flow. Then the guest room, bedroom, hallway, WC, and utility room could have a little less. Or I would probably prefer to completely turn off the utility room via the room thermostat since it is already too warm due to external heat (and I would like to direct the flow more toward the bathroom).
I’m just not sure whether it makes sense to adjust anything now again, or if I should wait until it stays around 5°C (41°F) 24/7 and the heating runs longer. Also, I’m curious about how the cycling behavior will develop—short loops like WC and hallway could act like a shortcut and cause the system to cycle frequently.
driver55 schrieb:
The house is from 2017, so 0.3 is clearly way too high. And where is the room target temperature specified?
Temperature difference between supply and return 1 K? 🙄Room target temperature is 23°C (73°F) because of the bathroom, and the temperature difference is 3 K with supply between 28-30°C (82-86°F) and return between 25-27°C (77-81°F).The heating engineer said the house was designed with a heating curve of 0.5?
KingJulien schrieb:
Maybe @Malz1902 meant a base temperature of 1°C (34°F)?
Perhaps an electric instantaneous heater for a short heat boost is an option? They are programmable.
I also just noticed that I can’t really get the bathroom warm without significantly throttling the rest. I don’t really want to do that, I don’t need a warm bathroom 24/7. Actually, I don’t even really need a particularly warm bathroom, but I don’t live alone 😉We have electric heating in the bathroom. The question is whether it’s worth it considering electricity costs. Is it better to run the electric heater or turn the bathroom radiator fully on, raise the heating curve a bit but throttle the other rooms, or lower the heating curve somewhat, allow more flow to the other rooms, and turn on the bathroom radiator only in the morning and evening?KingJulien schrieb:
Where is that? I haven't found it yet on my first search 😀Just keep searching. Yesterday, an option for a matte black standing panel was shown to me in the ads... there are definitely other great things out there. For example, infrared panels, which come in modern designs and styles without being intrusive.A
Alessandro28 Oct 2021 14:12Is your UWP set to constant pressure?
Alessandro schrieb:
Is your underfloor heating manifold set to constant pressure?Are you asking me? Then yes, it is set to constant pressureSo this morning it was 6°C (43°F) outside temperature instead of 9°C (48°F), with indoor temperatures nearly the same as at 9°C (48°F).
The target flow temperature at the heat pump controller is now half a degree higher at 6°C (43°F) outside temperature (23°C (73°F) instead of 22.5°C (72°F)) compared to 9°C (48°F) outside temperature. This supports my theory/conclusion about how much or in what ratio the flow temperature must increase relative to the outside temperature.
Now I would need two or three consecutive days with corresponding outside temperatures so that the heating system runs continuously for about 48 hours instead of only turning on at night.
The target flow temperature at the heat pump controller is now half a degree higher at 6°C (43°F) outside temperature (23°C (73°F) instead of 22.5°C (72°F)) compared to 9°C (48°F) outside temperature. This supports my theory/conclusion about how much or in what ratio the flow temperature must increase relative to the outside temperature.
Now I would need two or three consecutive days with corresponding outside temperatures so that the heating system runs continuously for about 48 hours instead of only turning on at night.
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