wrongisthenewright
commented
3 months ago This topic for computation temperatures discursion ;-)
Now, in cooling mode I have not found in the document the formula that applies. I understand that it cannot be the same as the slope configured has nothing to do, in the case of heating it goes from 0.2 to 1 and in cooling it goes from 0 to 30. They are very different values and I think that the same formula does not support these variations:
I was wrong, you're right, the cooling curves are different from heating.
these came from Italian manual low temp (fancoils) and high temp (underfloor cooling)
It's obviously an inversely proportional slope with imposed limits (limits btw that are function of the chosen slope) , the formula should be:
Tset_cooling = T_mand_min + SL/100*(40°C- Text)+OF.
So if you're on underfloor config, with a min temp of 18, no offset, slope 5 and ext temp of 30°C the value is: Tset_cooling = 18°C + 5/100*(40°C - 30°C) + 0 = 18.5°C
in case of fancoil config, with a min temp of 7, no offset, slope 25 and ext temp of 30°C the value is: Tset_cooling = 7°C + 25/100*(40°C - 30°C) + 0 = 9.5°C
Both values matches the graph.
It may be as you indicate, the point is that to simplify everything I have the offset parameters set to 0.
OK, this simplify the calculations, but the offset are there for a purpose, so you'll need to take them into account if you'll need to use them.
Finally, I believe that by simply applying your formula and making the temperature delivery fixed, we are losing some feature of the system.....
Choosing the right algorithm is not a matter of losing features, is mostly related to cost/savings and overall system configuration, in my case, given my needs and my home configuration I use a different configuration for cooling and heating.
In winter (heating) I use full automatic calculations with external and ambient probe. Having an hibrid system, once the energy manager has all the parameters chooses the LWT and then chooses to use either the boiler, the HP or both to get that temp, all based on the energy tariffs I inserted. In this way I always get the max savings in every instant.
In summer (cooling) I use a fixed temp configuration at the lower temp possible (7°C). If I'd have chosen the automatic calculations I may have had some extra saving because the HP could have run at lower frequencies (HP tend to perform better in term of COP/EER in the middle range of functioning frequencies), but I don't mind losing some KWh here and there because I have a PV and battery systems at home , so in summer I get my electric energy for free from the sun.
Please also be careful that the algorithm for LWT is only part of the equation. What you have to keep in mind is that HVAC systems treat thermal energy, not temperatures. There is also EWT to keep track of and the delta from LWT and EWT is proportional to the transferred energy. You can convey the same amount of energy with different medium (water) temperatures. You can heat an home to 20°C with the water at 40°C or with the water at 60°C, it depend on the thermal inertia of the home, the amount of water that flow (more water flow usually means more energy transfer) the exchange surface between water and air etc..
In heating keeping the LWT as low as possible is usually better for energy efficiency: for HP it means lower operating frequencies and thus better COP (the Nimbus COP can varies from 4/5+ at mid range to 2/3 at more than 60Hz). For boiler (at lease condensating ones) enhance the thermal energy recovery from exhaust fumes.
Another thing I have done is to ask different AI if they would give me a formula for heating and a formula for cooling using this data:
Interesting, but let's also take into account that the heating system of a home is one of it's core features. Commercial HVAC products may be overpriced and lacking some "finesse" but these are embedded system tested and mantained by professionals. I wouldn't leave the comfort of my home in the hand of a DIY algorithm that may run on an off the shelf HW that breaks down in the middle of the winter because some nerd put out the wrong update.
I'm into home automation allright and my being here it's a proof of that, but my heating is solely managed by the Ariston thermostat, the calculations made by the machine and my only intervention (apart from gathering metrics for reporting) is limited to change energy tariffs based on my contracts and PV production in winter.
ogkita
ysard
Hola @ysard, @wrongisthenewright.
This topic for computation temperatures discursion ;-)
Yes, I have read the installer document, about 20 or 25 times... I even generated the translated version from the Italian... It helped a bit, but do not think it helped a lot.
In the document, it explains how it works in heating mode. The formula... understood and there are no doubts. I hope to be able to check the values it calculates and uses next winter.
Now, in cooling mode I have not found in the document the formula that applies. I understand that it cannot be the same as the slope configured has nothing to do, in the case of heating it goes from 0.2 to 1 and in cooling it goes from 0 to 30. They are very different values and I think that the same formula does not support these variations:
For heating:
For cooling:
For heating. Simplifying and using only external probe:
Tset_term = Tmand_min +SL*( Tamb_set -Text)+OF. dove:
II must wait to winter to check if this is correct.
For cooling. Remember that I have not found the formula that applies in the document you indicate. Just changing the external temperature and the slope in the above formula we have:
I think it is not correct
The algorithm is influenced by various offset that must be taken into account when checking the temps. There is a heating (par 12.2.a1) and a cooling (par 12.4.2) compensation offset for LWT at HP level, this helps to deliver the right water temp at the zone manager in case the water gets cooled (in heating mode) or heated (in cooling mode) while the water is in transit from the HP to the zone manager for poor insulation or very long tubing.
It may be as you indicate, the point is that to simplify everything I have the offset parameters set to 0.
7f2b 7571 7572 7573
In addition, I have checked the following values in the menu and they are all set to 0:
For heating, these should not affect the cooling system: 4.2.3 4.2.4 5.2.3 5.2.4 6.2.3 6.2.4
For cooling, these are now the ones that should be affected: 4.5.4 5.5.4 5.5.4
7.3.0
Remember I configured this params at 0,
Finally, I believe that by simply applying your formula and making the temperature delivery fixed, we are losing some feature of the system.....
Another thing I have done is to ask different AI if they would give me a formula for heating and a formula for cooling using this data:
Current: External temperature. External humidity. Wind speed.
Forecast 3h: Outside temperature. External humidity. Wind speed.
Room: Current temperature. Target temperature.
Factors: Housing insulation level: 0-10, in order to be able to set several. Outside influence on the calculation: 0-10, so that several can be configured. Room influence on the calculation: 0-10, so that several can be configured.
Let's say that this could be as complicated as we want and the more data we have, the more optimal it will be...
Well, sorry for the talk... We are still working on it!
Thanks, Oscar