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?
R
RotorMotor18 Nov 2021 19:39OWLer schrieb:
I did not understand it. But I will increase it and observe. So down is a negative value after all. What do you want to achieve?
Fewer cycles (compressor lifespan) or higher efficiency (power consumption)?
tomtom79 schrieb:
How I came to that—I read it in the forum. If I write the name now, I will get another warning. But I’ll send you the link.
For understanding: if the water flows more slowly through the pipes, you get better heat output and efficiency.
By the way, we tried to achieve a temperature difference of 6 K with my heating system. I just trust the professionals on this, and I don’t mean the heating technicians. I would be very careful with that, especially when running a heat pump. They operate most efficiently at lower temperatures. Likewise, a larger temperature difference (delta T) is less efficient. A 6 K temperature difference is definitely not ideal. Of course, at some point, the electric consumption of the circulating pump exceeds the savings from lowering the temperature.
If the towel radiator runs all day, that’s understandable. Such a unit is not suitable for room temperature control. Using a fan heater for 5 minutes when needed is more likely to achieve the desired effect.
driver55 schrieb:
No. The integral is reduced by the delta between actual supply temperature and actual return temperature. Based on your description, the integral would only decrease once the floor heating is "recharged" again. But this already happens minutes after the compressor starts. Okay, learned something new again. And how does a higher actual supply temperature compared to the target supply temperature relate when there is a differential of 3-4°C (5-7°F) between supply and return at the same time?
A differential usually means heat output. If I’m releasing heat, the supply temperature shouldn’t rise higher than it’s supposed to, right? Or is the differential too low? I’ve often heard that 3-5°C (5-9°F) is optimal for a heat pump?
lesmue79 schrieb:
Okay, learned something new again. But in what context does a higher actual flow temperature compared to the target flow temperature make sense if there is simultaneously a differential of 3-4°C (5-7°F) between flow and return temperatures? Sorry, I just reread what I wrote. 🙁 That was obviously wrong.
Not flow/return. The delta between actual flow temperature and target flow temperature is correct.
Otherwise, with a differential of, for example, 6°C (11°F) and an energy input of -120 degrees minimum, the heat pump would only run for 20 minutes instead of 50-60 minutes.
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