welche Parameter für PI Regler

[Reason555]

Hallo zusammen,

ich bin gerade bei der Einstellung meiner Raumtemperaturregler - bisher mit mäßigem Erfolg (probiere aktuell mit den PI Reglern der Zennio Z38). Ich möchte daher auf des Regelung EIB PC umstellen und muss da allerdings zwei Parameter definieren, den K- und den I-Faktor.

K-Faktor: % Reglerabweichung bei 1° Temp.Differenz, Wert 100 wäre also Ausgang 100% bei 1° Temp.Differenz
I-Faktor: % Reglerabweichung bei 1° Temp.Differenz über 1 Minute, Wert 1 wäre also Ausgang 100% bei 1° Temp.Differenz über 100 Min.

Ich nutze eine Fußbodenheizung an einer Wärmepumpe. Es gibt auch zahlreiche Beiträge zu den Reglern an sich, allerdings keine in denen Beispiele für die Parameter genannt werden. Da aber sicherlich einige von Euch schon damit experimentiert haben gibt es sicher Erfahrungswerte.

Beste Grüße
Nils

[Uwe!]

also die "üblichen" Werte für FBH sind 5K/240Min. Das Ergibt eine relativ träge Regelung, was aber bei FBH einen gewissen Sinn macht, da die ja auch etwas träge ist.

Ich fahr meine FBH trotzdem mit 3K/60Min und bin damit sehr zufrieden.

Bei mir zwar mit einem TS2+, aber von den Paramtern her ist das eigentlich egal, ob TS2+ oder EibPC.

Noch ein paar allg. Infos:

Parametereinstellung => Wirkung

• P kleiner Proportionalbereich => großes Überschwingen bei Sollwertänderungen (u. U. auchDauerschwingung), schnelles Einregeln auf den Sollwert
• P großer Proportionalbereich => kein (oder kleines) Überschwingen aber langsames Einregeln
• TN

• kleine Nachstellzeit => schnelles Ausregeln von Regelabweichungen (Umgebungsbedingungen), Gefahr von Dauerschwingungen
• TN große Nachstellzeit => langsames Ausregeln von Regelabweichungen

[enertegus]

K-Faktor: % Reglerabweichung bei 1° Temp.Differenz, Wert 100 wäre also Ausgang 100% bei 1° Temp.Differenz
I-Faktor: % Reglerabweichung bei 1° Temp.Differenz über 1 Minute, Wert 1 wäre also Ausgang 100% bei 1° Temp.Differenz über 100 Min.

Hab das eben aus gegeben Anlass (Musterseite für Visuassistenten) selbst benötigt - vorher hatte ich das nicht gesehen:
Die Umrechung der üblichen Angaben 5Kelvin/120Min für das Makro wäre wie folgt:
K-Faktor=100/5Kelvin
I-Faktor= 100/120Minuten

[Warichet]

Hi Uwe,

Ich fahr meine FBH trotzdem mit 3K/60Min und bin damit sehr zufrieden.

Are you still happy with those values ?
How did you find those settings ? just by experiment ?

Any idea about the length of your hydraulic circuits ? the question is: does it have an impact on the settings ?
I've 2 rather long circuits (+/- 100m)
I've tried a bit, adjusting the pump speed between 2 & 3, no result.
I'm using the standard settings: 5K/240Min, but not very happy.

[Warichet]

Hi Uwe,

Your comments about the PI settings triggered some thinking.

Since the beginning of the installation of the underfloor heating system (warm water), 6 years ago, I've used the standard recommended parameters of the Merten 624944 RTR, that is 3K/200 for the PI algorythme (general recommendation is 5K/240).

Since the beginning I'm not very happy with the system, especially in automn and spring with quick outside temperature changes (in the winter it is OK). The plumber says "oh, that's normal". Great
I thought changing the boiler curves, angle and parallel, but I'm not convinced.

After some readings, I've still no definite clue. Nor Wikipedia nor the technical doc of the RTR, nor general purpose articles doesn't help.
Something hurts me: there are several types of underfloor heating, but they are all regulated with the same PI algorythme ? But in this algorythme, there is a "time" variable.
It has been said that a "anhydrite" system has a floor inertia of 1Hr/cm, and a classical "beton" system has a floor inertia of 2Hr/cm. Let's suppose we have a standard thickness of 3 cm (2.5 cm is the absolute minimum according to regulations), that yields an inertia of either 3Hr or 6Hr. Heck, quite a difference !

How is this integrated in the algorythme ?
What about the speed of the circulation pump ?

I finally adjusted the PI to 3K/90, looks much better, but I'm still interested in your comments or is it a "wrong" problem and, as the great plumber says "open the window when it is too warm"

[Uwe!]

Hi Raymond,

first of all, I'm sorry not seeing your post from March, 2nd.

And: Yes, over all I'm still happy with those values! The length of my hydraulic circuits differs from approx. 50m to approx. 120m. Not ideal, but well. That what my plumber did...

I guess that the pump speed won't show a big effect on characteristics of the underfloor heating system . You need a certain speed to get the needed performance, that's it.
Adjusting the boiler curves, angle and parameters is more important, in my opinion. Goal is always having the lowest but still adequate temperature.

last but not least: your plumber isn't completely wrong. A underfloor heating system will always be some how inert. (right word???)

The parameters 3K/60Min is an mix of thinking and trying. Goal was to make the underfloor heating system quicker. If it wood work with a concrete-System? I'm not sure but probably yes. I have also anhydrite.

By the way: before my kids go sleeping I open the window to get some cold air in :-)

Attachment:
the line shows the opening of the valve in %. The x-axis shows the hours. The bars are the Difference in 0,1°K to the setpoint value.

[Warichet]

Hi Uwe,

Yes, over all I'm still happy with those values

The length of my hydraulic circuits differs from approx. 50m to approx. 120m.

I think the length of the circuit, as such, is not a problem. If I take my example: different lengths correspond to differents rooms, since there is a RTR in each room, it should be possible to adjust accordingly.

I guess that the pump speed won't show a big effect on characteristics of the underfloor heating system.

The reason I mention it, is beacause of the "time" component of the PI algorythme. If we take the 3K/60 example, is it true that the measurements are re-actualized after 60 min ? If true, then it does matter if we achieve the goal temperature quicker. I think the circulation speed might infliuence the result, i.e. avoid to have a slack of cold water at the end of the circuit.

Adjusting the boiler curves, angle and parameters is more important, in my opinion.

Agree. That's why I want to put my Viessmann Funktionsbaustein to work. But before I proceed to such fine adjustements, I better make sure the basic settings are correct in all situations.

A underfloor heating system will always be some how inert.

Agree. I'm still looking for "best practices" about the rtr parameters.
What is you opinion about a floor inertia ? shouldn't it be part of the PI formula ?
If you have a pointer to good explanation about the PI, I'm taker

the line shows the opening of the valve in %. The x-axis shows the hours. The bars are the Difference in 0,1°K to the setpoint value.

Nice stuff .
I'd love to do the same, but I'm still strugling with the topic

[tbi]

Hi Warichet,

you wrote:

Since the beginning I'm not very happy with the system, especially in automn and spring with quick outside temperature changes (in the winter it is OK)

But in which special case this occurs. I assume you mean if the sun is shining ? Then it's to warm.

Or you mean is's sometimes to cold in autumn or spring ?

BR
Tobias

[Uwe!]

different lengths correspond to differents rooms, since there is a RTR in each room, it should be possible to adjust accordingly.

It's true that you can adjust by the RTRs quiet easily, but it's quite difficulty to adjust hydraulically!

If we take the 3K/60 example, is it true that the measurements are re-actualized after 60 min ?

NO! Recalculation takes place every few Seconds (30s with the TS2+ I guess)

What is you opinion about a floor inertia ? shouldn't it be part of the PI formula ?

I'm not sure! It should be adaptable by the normal parameters. More important would be the set a "Arbeitspunkt" thus the % value won't go to 0 if the temperature is reached!

If you have a pointer to good explanation about the PI, I'm taker

At least not in English!
Few years ago I made a little excel sheet to see how different parameters behave. That helped me!

[Gaston]

The parameters 3K/60Min is an mix of thinking and trying. Goal was to make the underfloor heating system quicker. If it wood work with a concrete-System? I'm not sure but probably yes. I have also anhydrite.

Such extreme Parameters while wrong in regard of the regulated system are required by the bad design of todays PI regulators.

Cheers,
Gaston

[Warichet]

Hi Tobias,

But in which special case this occurs. I assume you mean if the sun is shining ? Then it's to warm.
Or you mean is's sometimes to cold in autumn or spring ?

I did experience both scenarios, but don't remember exactly in wich circumstances.
At that time, I failed to do a rigorous analyze. I was frustrated to have such an expensive system and to have such poor results and hearing everyone telling me "it's normal". Note, they say it afterwards , not at the time of purchase.

I guess you want to pin-point the overshoot ? it's probably due to my inadequate PI parameters, that is heating when it's already too warm.
I'm curious to see the effect of the new parameters over a several weeks time.
I'm a bit scared by extreme parameters, so I settled for the 3K/90.
Any comments ?
A pointer to a "Best practice" guide ?

[Warichet]

It's true that you can adjust by the RTRs quiet easily, but it's quite difficulty to adjust hydraulically!

Maybe we have to go OT.
Looking at the hydraulic distribution box, I've the red pipe as arrival of hot water (the blue pipe is return of cold water). Each connection of a circuit has a kind of valve which can be mechanically adjusted (the doc says equalized) with a hex key. Here I can compensate for the difference in circuit lengths, that is, for the short circuits, I close the valve 1/4 turn

NO! Recalculation takes place every few Seconds

Is it that what they mean by "continuous PI" ?
But in the 3K/60, what is this 60 exactly ?

(30s with the TS2+ I guess)

Is that a parameter of your RTR of a hard-coded value ?

More important would be the set a "Arbeitspunkt" thus the % value won't go to 0 if the temperature is reached!

I don't have this "Arbeitspunkt" in a Merten RTR, probably other wording, I've to check again.

At least not in English!

I prefer a good document in german then a poor document in english.

[Warichet]

Such extreme Parameters while wrong in regard of the regulated system are required by the bad design of todays PI regulators.

Ouch !
Guess who thought that Merten was "top notch" ?

[Gaston]

Ouch !
Guess who thought that Merten was "top notch" ?

This is not linked to any brand, they all work the same with slight differences in the behavor ate the extrema (0% & 100%).

[Uwe!]

Here I can compensate for the difference in circuit lengths, that is, for the short circuits, I close the valve 1/4 turn

Correct! But if you have a circuit with 20m and one with 120 m you won't be able to regulate the short one to 0,5l/h und the large one to 2,5l/h. The adjustment range is to small!

But in the 3K/60, what is this 60 exactly ?

Exactly? Good question! Ask Gaston! It is how fast you will reach 100%.

Is that a parameter of your RTR of a hard-coded value ?

hard-coded

I don't have this "Arbeitspunkt" in a Merten RTR, probably other wording, I've to check again.

Oh yes, you have. It's 0 as it is by every RTR on the market. But it should be somewere around 70% or 80%. The value which would be nessasery to keep the wanted temperature. RTRs are starting to go down to 0, as soon as they reached the wanted temperature.

I prefer a good document in german then a poor document in english.

maybe you take al look here first:
https://knx-user-forum.de/downloads.php?do=file&id=229