Network issue or dead 5512RVF

Hi guys

I'm hoping someone can help confirm what's going on with my C-Bus install - I suspect it is a dead 12-channel relay, but happy to be convinced otherwise!

My C-Bus system was installed about 3 years ago. Layout is a main distribution board at the front of the house, and a sub-board on each of the three levels. Each board has 1, 2 or 3 C-Bus output units installed. The C-Bus data cable is a star topology from the main board to the sub-boards, and then daisy-chained from each sub-board to all the switches on that level. My electrician did all the cabling/install, I supplied the C-Bus hardware and did the programming. This setup has been working perfectly fine up until a few weeks ago, until the following symptoms appeared:

• Some lights on the first floor would occasionally flicker or go out, only to come back on anywhere from a few seconds to a few minutes later. The LEDs on the relevant switches stayed lit when this happened. This happened very occasionally, but increased in occurrence to perhaps once every few days. The affected lights were on an 8-channel dimmer, not the 12-channel relay (These are the only two output units on the first floor).
  
• I then started noticing that lights would be off, but the LED indicator on the switch would be lit, ie I'd go downstairs leaving lights on upstairs, then when I went back up later, the switch plate would be lit but the lights out. Pressing the switch off then on again would turn the light back on. This became a multiple times per day occurrence, but only affecting the first floor. At this point, I was thinking there was an issue with the 8-channel dimmer.
• About a week ago, all the output units in the house stopped responding one night. Lights that were off could not be turned on and vice versa. The local override buttons on the 1st floor and ground floor output units weren't responding. About 15 minutes later, I went to the main board near the front door, and tried the single 5504RVF and it worked. All the lights in the house at that point started working normally again.
• Late last week, some of the LEDs on the first floor switches started flickering intermittently. Around this point, the 12-channel relay, which looked like it had been behaving up to this point, just stopped working. Three lights were on from this unit and could not be turned off by the relevant switches, nor the local override buttons. Neither could I turn on any other lights from this relay. Both the unit light and the C-Bus light on this unit are out, but the 3 local override buttons remain on (see photo attached). None of the local override buttons work. I've tried flicking the breaker for this unit, but when I turn it back on, it remains in its unresponsive state. Because one of the lights stuck on is my bedside lamp, I've had this unit turned off at the breaker for the past few days.
• Since then, the rest of the lights upstairs (on the 8-channel dimmer) seem a little more stable. I still have had occurrences of lights turning themselves off, but it's not as frequent. Like before, I sometimes can't turn them back on for a few minutes. The fact that it is still occurring though bothers me, and is making me wonder if there is a network issue, or if the dimmer is on the way out too.

Some further information that may be helpful:

• There are 34 units on the network.
  
• I have three clocks enabled, one on a unit in each sub-board. The relay in question does not have the clock enabled, but the dimmer mentioned does.
• I have one hardware burden, installed in my PACA (also used as a PC interface when I fire up toolkit), located in the basement.
  
• According to toolkit, current consumption is 524mA with a supply current of 1600mA. Impedance is 406 ohms.
• Power supplies are well distributed (all embedded in output units). When I run the diagnostics, unit voltage is pretty constant across the whole network, with a low of 30.2V and a high of 31.6V.
• All C-Bus units were bought new, except the 12-channel dimmer and 8-channel relay used on the first floor, can't remember the manufacturing date of these two units (when was green a C-Bus colour?!), but they are probably 8-9 years old. Was a bit short on cash at the time...might be paying for it now though!
• The only logic in the PACA is a schedule for turning on 4 or 5 lights at sunset, and then back off again around midnight. Two of these lights are running from the dimmer on the first floor.
• I've checked for loose connections in the relay, all good.
• In the first floor sub-board, the C-Bus cable from the main board goes into the 12-channel relay, then to the 8-channel dimmer, then to all the first floor switches. Even with the relay powered down, the network still works and scans fine, presumably because the two RJ45s in the unit are physically connected together.

The only other potentially relevant detail is that about two months ago, we had mains supply issues. Voltage would drop enough to cause lights to dim and flicker (actually, constantly flicker at times). Some neighbours (no C-Bus) reported the same issue. Once the power company fixed a dodgy connection at the pole, the issue stopped. They confirmed it was just affecting the one phase, which my house happened to be on. Don't know if the under-voltage could do any damage.

Anyway, sorry for the essay (I work in software development and appreciate detailed bug reports...) My expectation is that the 5512RVF needs to be replaced, and possibly the dimmer. But thought I'd put it out there in case there is something else that I've missed.

Thanks in advance.
Paul

 

So last night the network went nuts. Connectivity was really flakey throughout the whole house, with switch buttons flashing, toolkit scan failing, etc. Toolkit eventually pulled back enough info for me to tell that the active clock was on the first floor dimmer. After several attempts, I was able to disable the clock from that unit (leaving two other clocks). Toolkit was also reporting that my PACA had a software burden enabled, even though the address was 002. Once I disabled the software burden (I have a hardware burden in the PACA), the network seemed to stabilise and work properly.

However, I was still noticing issues with the first floor lights, ie the lights connected to the dimmer would go out, but the switch LEDs would remain lit.

And this morning the network went nuts again for a few minutes, with switch LEDs flashing all over the place. After being perfectly stable for 3 years, I don't get what's going on now. Any suggestions?

Cheers
Paul

 

First thing I noticed from the photo in your first post was there was the C-Bus and Unit LED are not illuminated.
This would indicate no clock and mains power on that unit. which is strange given the fact the other LEDs are illuminated (hence implying there is mains power).
Software burden restriction to unit address 001 only applies to Output units not system support units eg PACA
The aqua coloured units are probably 15 + years old
I would be suggesting that you are loosing C-Bus clock in the first instance. This could be due to clock failure or and possible more likely C-Bus voltage dropping to low or even to zero volts
There are some training manuals still floating around the internet with fault finding sections and charts which may help.
Heres one I found
http://automatedhome.dp.ua/wp-content/files/C-Bus_Basics_Training_Manual_Vol_2.pdf
Colin

 

Thanks for the suggestions Colin. I'll check voltage levels with the multi-meter and report back.

This morning the upstairs lights went nuts again, so I watched the lights on the output unit whilst it was happening. The unit light was flashing, or perhaps more specifically, was going out and coming on again, as it wasn't entirely regular. I have some lamps plugged into regular GPOs that weren't showing any signs of flickering, so I don't think there is a 240V supply issue. The switch LEDs stayed lit the whole time, suggesting there were no network messages turning off/on lighting groups. My money is still on the relay being dead and the dimmer in its death throes, putting noise on the bus and messing up the clock.

In searching the archives, I found this thread /threads/c-bus-errors-diagnostic-help.8429/ which sounds very similar to my issue. On the weekend (ie when I'm around home in the daylight and don't need to put lights on), I'll unplug the two upstairs C-Bus units from the network and observe the effect on system stability.

 

Well it looks like I got to the bottom of it, although I'm not completely sure of the cause...

TL;DR The relay and dimmer are fine, it was a switch on the fritz that caused the problem.

I decided to split the network into two at the first floor sub-board, so that whatever was happening upstairs wouldn't cause grief in the rest of the house. As I mentioned in my first post, the C-Bus cable from the main board goes to the relay in the first floor sub-board, then a short link to the dimmer, then to a daisy-chain of all the first floor switches. The plan was to just unplug the cable coming from the main board. In the process, I briefly unplugged the cable from the dimmer going to all the first floor switches, and immediately the "dead" relay came back to life! I plugged it back in a couple of seconds later and the relay died again. I unplugged it again and the relay was resurrected once more! I then plugged the cable from the main board back into the relay and both the relay and dimmer remained operational.

At this point I thought I knew what was going on - somewhere along the daisy-chain of first floor switches there must be a fault - that's fine, I can check each switch until I figure it out. By now a few minutes had passed, so before putting the cover back on the sub-board, I thought I'd plug the cable back into the dimmer just for kicks, expecting the relay to die again. But it didn't! And everything was still working fine! The only explanation that I can think of is that by disconnecting all the first floor switches from the dimmer, they were powered off completely. A few minutes of no power to which ever switch unit was playing up was enough to get it out of its fritz, so that upon reconnecting and powering up, it started behaving sensibly. It could be that I have a switch (SC5034NL) on the way out that needs replacing, or it could have just been some temporary issue. I figure it can't be a cable fault, otherwise the problem should have occurred again pretty much immediately. I'm not going to worry about it unless it happens again, at which point I'll try to isolate the problematic switch.

But I am curious as to how a switch can put enough noise on the network such that a C-Bus output unit can be completely unresponsive, including from local override buttons. I get it not responding to network commands, but local overrides?? Maybe I just put it down to it being an old relay that perhaps isn't as robust as more recent versions...

 

Are any of your switches from the same era as the aqua coloured dimmer. If so there was a couple of faults that took years of service to develop the fault and caused problems on the network.
Do check your wiring and especially any cable that may be exposed to water/ outside. maybe a cable that was not terminated for something planned for the future

 

Quite possibly! I bought most of my switches (SC5034NL) second-hand to keep the cost down, figuring I'd replace them gradually as needed. Can't remember the exact manufacturing dates, but most of them pre-date the blue LEDs, although from memory, I don't think any were pre-2005. Do you know the date/serial number after which they were considered good?

And you're right, I do have 3 un-terminated cables for future use! I'll check them over the weekend. Thanks for your help with this.

Cheers
Paul

 

Cannot remember the exact dates but it was before your dates.