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?
Hausbau 55 schrieb:
In general, with Vaillant heat pumps, the operating time can be influenced through the energy integral.lesmue79 schrieb:
The compressor hysteresis is already set to maximum, as is the energy integral. Unfortunately, on my heat pump, the energy integral can only be set up to 120 minutes (2 hours), while other Vaillant heat pump models allow up to 180 minutes (3 hours). When temperatures drop to around -5°C (23°F) or below, it runs continuously 24/7.One more time the question: What exactly do the energy integral and compressor hysteresis mean, and how do I use them to influence efficiency?
My system is running with factory settings:
R
RotorMotor18 Nov 2021 18:58I would understand it this way: the "Vaillant" energy integral affects how much the heat pump overheats to extend the cycling intervals.
So, for example, if you increase it to -120, the cycles become longer.
The advantage might be a longer service life, while the disadvantage is a slightly higher consumption due to increased flow temperature.
The compressor hysteresis also seems to be a temperature differential for the compressor.
I think here as well, a higher value results in longer but somewhat less efficient cycles.
So, for example, if you increase it to -120, the cycles become longer.
The advantage might be a longer service life, while the disadvantage is a slightly higher consumption due to increased flow temperature.
The compressor hysteresis also seems to be a temperature differential for the compressor.
I think here as well, a higher value results in longer but somewhat less efficient cycles.
I can't fully explain it myself because I haven’t completely internalized it yet.
The energy integral is based on the difference between the target supply temperature and the actual supply temperature (sometimes called degree-minutes).
The compressor/heat pump starts heating at -90 minutes. If the system eventually stops delivering heat because the rooms have reached their desired temperature, the actual supply temperature rises above the target supply temperature. This difference, let’s say 1.5 degrees Celsius (2.7°F), counts as one degree-minute.
This 1.5° then ticks down by one degree-minute each minute from the set -90 minutes down to 0°, at which point the system switches off.
If the opposite happens and the target supply temperature falls below the actual supply temperature, it moves in the other direction until the system restarts heating at -90 minutes.
In addition, there is a compressor hysteresis as extra protection, for example 3K (3°C / 5.4°F), if the actual supply temperature rises quickly. Then the compressor switches off when the actual supply temperature is 3°C (5.4°F) above the target supply temperature.
In brief:
A high compressor hysteresis results in longer system runtime (mine is set to 15°C (27°F) or Kelvin).
Increasing the compressor start time also leads to a longer runtime, because it then takes longer for the system to start and stop working. Mine is set to 120 minutes.
I hope I was able to explain it somewhat clearly, though I can’t guarantee it’s 100% correct. I’m not a professional.
The energy integral is based on the difference between the target supply temperature and the actual supply temperature (sometimes called degree-minutes).
The compressor/heat pump starts heating at -90 minutes. If the system eventually stops delivering heat because the rooms have reached their desired temperature, the actual supply temperature rises above the target supply temperature. This difference, let’s say 1.5 degrees Celsius (2.7°F), counts as one degree-minute.
This 1.5° then ticks down by one degree-minute each minute from the set -90 minutes down to 0°, at which point the system switches off.
If the opposite happens and the target supply temperature falls below the actual supply temperature, it moves in the other direction until the system restarts heating at -90 minutes.
In addition, there is a compressor hysteresis as extra protection, for example 3K (3°C / 5.4°F), if the actual supply temperature rises quickly. Then the compressor switches off when the actual supply temperature is 3°C (5.4°F) above the target supply temperature.
In brief:
A high compressor hysteresis results in longer system runtime (mine is set to 15°C (27°F) or Kelvin).
Increasing the compressor start time also leads to a longer runtime, because it then takes longer for the system to start and stop working. Mine is set to 120 minutes.
I hope I was able to explain it somewhat clearly, though I can’t guarantee it’s 100% correct. I’m not a professional.
RotorMotor schrieb:
I would understand it as the "Vaillant" energy integral affecting how much the heat pump overheats to extend the cycling intervals.
So, for example, if you increase it to -120, the cycles become longer.
An advantage might be a longer lifespan, while a disadvantage is slightly higher consumption due to an increased flow temperature.
The compressor hysteresis also seems to be a temperature differential for the compressor.
I think a higher value here means longer but somewhat less efficient cycles. Partly correct.
Yes, the integral towards -120…-180 extends the cycles. You could also say the room target temperature experiences slightly larger fluctuations.
However, this has no effect on the flow temperature, as it is determined solely by the outdoor temperature (of course still depending on heating curve, room setpoint temperature, but those remain unchanged).
My Vaillant 63/2 from 2008 does not have compressor hysteresis.
R
RotorMotor18 Nov 2021 19:31driver55 schrieb:
However, this has no impact on the supply temperature, as it is determined solely by the outdoor temperature. If the heat pump runs at minimum capacity for 2 hours instead of 1 hour, for example, the actual supply temperature will naturally increase.
So, there is slightly less efficiency due to fewer heating cycles.
There has to be some downside, after all.
But you should be careful not to get too theoretical here. 😉
lesmue79 schrieb:
The compressor/heat pump starts heating at -90 minutes. If the system at some point stops delivering heat because the rooms have reached their set temperature, the actual flow temperature rises above the target flow temperature. This difference, let’s say 1.5 degrees Celsius (2.7°F), is then called a degree-minute.
These 1.5° accumulate each minute from the set -90° down to 0°, at which point the system switches off.
In the opposite case, if the target flow temperature falls below the actual flow temperature, it goes the other way until at -90 minutes the heating starts again. No. The integral is reduced by the delta of actual flow minus actual return temperature. According to your description, the integral would only start counting down again once the floor has been "recharged."
But this already happens minutes after the compressor starts.
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