Which settings for FBH, thermo devices

[Warichet]

Hi,

Can someone help me to select the best settings, for a FBH regulation ?
I've a Merten 624944 RTR, thermo devices for controlling the valves, a standard Merten actuator and a FBH with 3Hr inertia.

The doc of the RTR explains each parameter, but few examples for FBH (the examples for warm water radiators and EMO are OK).

I've attached the main config screens, there are so many, I haven't put them all.

Thank you for your advice.

[Warichet]

I guess the Merten 624944 RTR are not very popular for a FBH

Too bad

[tbi]

Hi Warichet,

were is your problem ?

You can configure a PI-Control or a 2-step control.

The PI is a propotional integral controler which has normaly a continues output.

In general the the valves a thermo ones. Means binary open or closed. They can't handle continues signals.

The PI controler continues output must be modulated by PWM (puls wide modulation) . This can be done in the RTR or in the heating KNX aktuator.

If configured in the RTR the binary GA (open/closed) will be send direkt to the heating aktuator like 15 min cycle time. 66% in then 10 open and the 5 min closed, 10 min open, 5 min closed .....

Here you see only the open closed GA on KNX BUS.

If the PWM is configuered in the heating aktuator the RTR will send the percentage 0-100% valve position on the KNX bus to the heating aktuator. The heating aktuator transform this (example here 66% to the PWM cycles of open and closed (10 min open , 5 min closed, 10 min open , 5 min cosed, ..... till the percentage value is changed.

Th 2 Step- control is very simple, if heating required => valve open otherwise=> valve closed.

Regards

Tbi

[swenga]

Hello,

i'm using the bigger brother of the Merten RTR (6287xx) together with the Jung 2136 TRIAC heating Actor and stupid Thermo-Drives. The RTR uses continous PI-mode and works perfectly with the actor and drives.
I only uses the standard parameter (in your screenshot "underfloor heating") which expects 5K in 240min.

best regards, Swen

PS: In my opinion the feature of setting minimum/maximum values for the output signal, seperately for cooling/heating is pretty handy (and i miss it at the GIRA).

[Warichet]

Hi Tbi,

Thank you for taking the time to reply.

were is your problem ?

My problem is that I'm lost in the many config screens (although I shouldn't complain about the rich features of a product) and my lack of basic knowledge of regulation prevents me to select the right combination for the case at hand.
Also, I've provided much details, hoping for an ad-hoc solution.

You can configure a PI-Control or a 2-step control.

Indeed, that's what I read from the doc. My complaint was about the lack of practical examples about FBH, the newbee is lost

The PI is a propotional integral controler which has normaly a continues output.

I understand this is NOT appropriate to my case

The PI controler continues output must be modulated by PWM (puls wide modulation) . This can be done in the RTR or in the heating KNX aktuator.

You are touching the core of the problem.
The RTR does not have an option "PWM" or at least not labeled as such.
As mentionned above, I intended to use a standard actuator (if possible).

If configured in the RTR the binary GA (open/closed) will be send direkt to the heating aktuator like 15 min cycle time. 66% in then 10 open and the 5 min closed, 10 min open, 5 min closed .....

I understand, but as mentionned above, I've a standard actuator.
Does it imply that I've either to buy a new RTR or a new heating actuator ? In other words, my proposed config is no good ?

The 2 Step- control is very simple, if heating required => valve open otherwise=> valve closed.

So simple ?
Why bother to something else then ?

Thanks again.

[Warichet]

Hi Swen,

i'm using the bigger brother of the Merten RTR (6287xx) together with the Jung 2136 TRIAC heating Actor and stupid Thermo-Drives. The RTR uses continous PI-mode and works perfectly with the actor and drives.

So, I'm asking myself if I hadn't better bought a heating actuator. This implies routing the EIB cable to the location of the heating actuator, which is not the case for the moment, I've installed a 5x0,75² for controlling the Thermo-Drives.
I understand from previous posts that my intended setup is not the best idea

Thank you

[swenga]

Hello Warichet,

i also don't see your problem:
Parameterize the RTR to do just "one step heating", put the mode to "continous PI" and put the "underfloor heating" in. The RTR now sends out %-values for the actor, the actor itself (must of course be a heating-actor) converts that via pulse modulation to on/off signals for the standard binary thermo drive on the vent.

I dont have the knx heating actors in the heating distribution box but a n*0.75-Wire coming from the KNX cabinet to the heating distribution box, where each individual thermo drive (or in some cases more than 1 when two or more heating circuits belong to one room) is connected to.

Avoid 2-Step control (PI-control tries to compensate for the over-reaction which happens when just doing 2 step).

What type of heating actor do you have?

So long, Swen

[tbi]

As mentionned above, I intended to use a standard actuator (if possible).

Not a good solution. Heating aktuators uses triacs not simple relais. Triacs have a much better life time and this actuators have also a PWM included.

So simple ?
Why bother to something else then ?

Diskuss with only yes and no. you will see the altitude of the discussion will be high. Same here, if the valve is 100% open till the temperature is reached, you will have every time a swing over. This is not very nice.

The PI hat values between 0 and 1 and if there it is setup correct, you don't have swing overs or offsets.

So prefer this, if you can.

Do you see in the PI-continues setup a binary output ?

Regards

Tbi

[Uwe!]

You are touching the core of the problem.
The RTR does not have an option "PWM" or at least not labeled as such.
As mentionned above, I intended to use a standard actuator (if possible).

I didn't read the docs for your RTR, but the "switching PI controller" configuration should be what you are looking for. The RTR calculates by PI-method a %-value and makes this by PWM to an On/Off for the actuator. This would work even with a normal actuator. But as tbi said, this could be a problem for the durability.

[klaus407]

Hello Warichet
Voilá, this is what you need. Although a pure heating actuator is to be preferred you can do it with a normal one, specially if you´ve got a spare channel and you don't want to buy a whole four or six channel heating actuator for just one circuit.

[Warichet]

@swenga

put the mode to "continous PI" and put the "underfloor heating" in

I think this is inapropriate to my case.

What type of heating actor do you have?

As mentionned above, I've a standard Merten actuator, which I intended to use (unless convinced to drop it and buy a heating actuator.

@tbi

Not a good solution. Heating aktuators uses triacs not simple relais. Triacs have a much better life time and this actuators have also a PWM included

OK, I understand, although I was hoping for a cheaper solution.

if the valve is 100% open till the temperature is reached, you will have every time a swing over. This is not very nice

I agree, this is explained in the doc.
But is it relevant to the case of a FBH ? with such a laaarge inertia (3Hr) does it really matter ? Those "extra" would be "absorbed", unless you mean that this "swing over" will have a negative impact on the power consumption (I think it will not be noticed at the comfort level).

Do you see in the PI-continues setup a binary output ?

I thought I should avoid "anything continues" as I'm using thermal devices which can only operate On/Off (as opposed to EMO).
To answer your question:
under the heading "two step heating"
under the heading "continuous PI controller", I see:
continuous PI controller
switching PI controller
continuous 2-step control
switching 2-step control
Could it be that "switching PI controller" = PWM ???

@Uwe

but the "switching PI controller" configuration should be what you are looking for. The RTR calculates by PI-method a %-value and makes this by PWM to an On/Off for the actuator. This would work even with a normal actuator. But as tbi said, this could be a problem for the durability

Got it !
I understand very quick, just that you have to explain 5 times

@klaus407
"this is what you need."
Thank you very much.
Can you please confirm that "switching PI" = PWM ???

specially if you´ve got a spare channel and you don't want to buy a whole four or six channel heating actuator for just one circuit

Right to the core.
It's even worse, as I eventually need 1 dual channel actuator at one place and 1 single channel actuator at another place.

Thanks to all for your time and patience.

[Uwe!]

But is it relevant to the case of a FBH ? with such a laaarge inertia (3Hr) does it really matter ?

It matters especially by a FBH!
Example: your valve is 100% open, temperature is rising slowly. At the point the desired temperature is reached you were heating still at 100% and switch now to 0%. The FBH will heat the room for the next few hours and you maybe will get 1-2K above target.

[Warichet]

It matters especially by a FBH!

Lesson learned, Sir !
(guess who is looking for a Theben HMG)

[makki]

For exactly this reason, I expanded the PI-RTR-Baustein to deal with actuators not able to process 1byte values and output 0/1 cyclic.
Downloadable somewhere here, my actuators (17xFBH, not willing to pay for these) is a dumb UK/S 32.1+SSR relays..

But using common actuators with a physical relay might not be that future-proof.. It has to die within some years, thats not what I wanted..

Makki

[Warichet]

For exactly this reason, I expanded the PI-RTR-Baustein to deal with actuators not able to process 1byte values and output 0/1 cyclic.

Clever trick !

(17xFBH)

ûûûh !

is a dumb UK/S 32.1+SSR relays..

and the UK/S is able to drive the input current to the SSR ? Which kind of SSR are you using ?
I thought the output current of the UK/S is just a couple of miliAmps.
Nevertheles, clever trick !
I feel concerned about the maintainability of my system (by someone else then me), hence I try to use standard solutions whenever possible.

Thank you for this interesting feedback.