KNX/EIB Merten 648729 Jalousieaktor

[Warichet]

Hello,

I'm plagued since day 1 with a problem in the Merten 648729 Jalousieaktor REG-K/4x24/6 mit Handbetätigung.

I've 2 of those actuators, they are used to control 4 Velux windows and shutters. Under normal conditions, they work just fine.

The problem is: after a general power loss, they loose their status, and a a new position status request doesn't work. An actual action/move on each window & shutter brings the status again in sync.
According to Merten's TechSup, it's due to the fact that part of the actuator's logic supply is coming from the auxilliary power instead of from the bus. The recommended suggestion is to put the actuators on UPS. Giving my environment, this is not a valid option. I'm considering buying 2 new actuators.
The question:
Can someone recommend a Jalousieaktor 4x24V which is still working fine after a power loss ? Those "details..." are usually not in the specs , but maybe someone can comment on practical experience ? I mean, having done it !

Maybe you guys don't have power loss ? . I get it sometimes 3 times in a week.

[Warichet]

Hi,

I'm still puzzeled about this issue.

I wonder, is it possible for an actuator to "know/remember" it's position before the power loss ?

If the answer is "No", it makes no sense to replace the actuators.
Any comments, please ?

Also, in the HS, I could mark the GAs about the position as "remanent".
Would that be a good solution ? although it doesn't give any guarantee about the actual actuator position as the Velux has no external switches.

Thanks

[MatthiasS]

Marking a GA as rememanten does not have an effect on the actuator itself. I think, this will not solve your problem.

I think, no actuator will know the position of the blinds after "booting". This is only possible with drives that have a measuring system.

[Warichet]

Marking a GA as rememanten does not have an effect on the actuator itself.

Understand

I think, this will not solve your problem

Yes and no. My main problem is that the Visu doesn't reflect the real situation after a power loss. The first time I've seen all windows open, I was really in panic.
In summary, after the power loss, I get a status "0", which is "Open", hence the Visu shows the window in a state "Open", although the window is closed.
If the status gets carried over after a power loss (I guess it is the purpose of the flag "remanent") I wouldn't see this effect. Right ?

I think, no actuator will know the position of the blinds after "booting". This is only possible with drives that have a measuring system.

You are probably right. Although modern devices could host a 16 Bytes NVRAM, no ? Instead of those actuators having 36 features which most of us don't use, I would appreciate a status that reflects the real world.

[Warichet]

Hi,

Reply from Merten's TechSup

In the new actuator 648704 the problem was eliminated.
So when the 24v supply is lost, the status will be saved.

[MatthiasS]

You are probably right. Although modern devices could host a 16 Bytes NVRAM, no ? Instead of those actuators having 36 features which most of us don't use, I would appreciate a status that reflects the real world.

The real world is the problem. Maybe the actuator has manual switches. How can the actuator notice this during bus power down? Maybe there are other use cases as well.

So storing the actuators state is not the problem, this can be fixed easily. But the actuators state is not the state of the real world in many cases.