ᐅ What supply water temperatures are you currently using?

Created on: 24 Oct 2021 10:27
L
lesmue79
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?
tomtom7920 Nov 2021 19:32
15 starts didn’t even affect my on/off heat pump.

@Malz1902

Do you perhaps still have the phase shift included?
R
RotorMotor
20 Nov 2021 19:34
Where do you get the information about what is considered a lot and what is little? One person says it’s no problem at all, another says it’s too much. Are there any reliable data available on what a heat pump can handle and what it cannot?
G
guckuck2
20 Nov 2021 19:58
In theory, the unit lasts for about 100,000 compressor starts. You can do the rest of the math yourself.
15 starts per day – during the heating season – isn’t great but also not a disaster in my opinion.
R
RotorMotor
20 Nov 2021 20:06
Where did you get the 100,000 from?
That should easily last 30-40 years.
M
Malz1902
20 Nov 2021 20:13
tomtom79 schrieb:

15 starts doesn’t even match my on/off heat pump.

@Malz1902

Do you maybe still have the parallel shift enabled?

The characteristic curve offset is set to 0.
More words.
OWLer20 Nov 2021 23:37
guckuck2 schrieb:

15 starts per day – during the heating season – is not great but also not a disaster in my opinion.

Today I will probably have between 25-30 starts at 9-14°C (48-57°F) outdoor temperature. Let’s see if I can increase the energy integral even further.


Time series: Blue = consumption, Yellow = directly consumed; peak around 5:00 AM, low values.


Let’s see what happens in the next few days as temperatures continue to drop.