Posts: 167
Threads: 20
Joined: Apr 2017
Reputation:
2
Did you check in ETS monitor, check what happend on the KNX bus traffic?
maybe to much traffic on the KNX bus why LM got to heat?
Posts: 94
Threads: 29
Joined: Nov 2020
Reputation:
1
I checked, it seems like there's no traffic at all, only a few messages on the bus.
Could it be a short circuit on a branch or something like that?
Posts: 7720
Threads: 42
Joined: Jun 2015
Reputation:
446
Have you measured bus voltage and current? If the current consumption is high then maybe one of the devices if faulty.
Another possibility is a loose cable or an incorrect connection somewhere.
Posts: 94
Threads: 29
Joined: Nov 2020
Reputation:
1
12.04.2022, 07:47
(This post was last modified: 12.04.2022, 08:36 by Kilogica.)
I'm not at the site right now but there was one of the electricians yesterday, he measured 29 V on the bus but I don't know if he measured the consumption.
Thanks for the tip though, I'll check it ASAP.
I suspect that there is a faulty connection somewhere, maybe a rat or something ruined the bus cable, but it's really hard to find.
Another possibility is that the power supply or the webserver are faulty, but it sounds really strange because I know that they worked at the time I programmed the system.
Posts: 4572
Threads: 23
Joined: Aug 2017
Reputation:
206
Maybe add a repeater and new psu for this branch.
------------------------------
Ctrl+F5
Posts: 94
Threads: 29
Joined: Nov 2020
Reputation:
1
Yes, that's what we've done just a minute ago and it seems to work.
The question is: what could possibly cause that kind of behaviour? I can't figure it out...
Can't be a short circuit because power supply and all the devices seems to work.
Can't be cable length because, according to what the electrician said (but we estimated the same thing), it is under 350 m.
There is a star with 5 branches but only one seems to cause problems, we changed the bus cable and we tried even with a zipline minimizing the distance...it didn't work so can't be the cable integrity.
Can't be webserver or PSU because we changed them.
Can't be number of devices because there are only 19 including the repeater.
This is really insane for me, I feel like a ghosthunter...
Posts: 7720
Threads: 42
Joined: Jun 2015
Reputation:
446
Star topology with long cable length can cause issues because the signal is reflected on each branch. As Daniel said adding a line coupler can help.
If you have an oscilloscope you can check the how the signal looks on all branch ends.
Posts: 94
Threads: 29
Joined: Nov 2020
Reputation:
1
It sure helped adding a line coupler as a repeater, but it's really really strange because we had bigger installations with star topology and no problem at all.
Maybe some field singularity but who knows.
Thank you all for helping though!