CBUS problems - the ones that are hard to diagnose!

My self and my company have been dealing with CBUS in the UK for over 20 years.

In recent years we have been contacted by many clients with intermittent CBUS problems. Some are relatively easily solved others are more problematic and we are increasingly finding the customer does not have the funds to employ our services to get to the bottom of the problems and hence they reman unsolved.

We currently have a case in point that has very bad intermittent problems and I'm hoping that someone will provide some guidance on what steps to take next.

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Fault - random I have witnessed it
- many channels (on rare occasions all) but not all come on
- system locks up LED's on switches on do reaction from buttons will clear witin spce of 5 min !
Standard CBUS install - relays, dimmers, saturn switches an old b&W touch screen, RS232 interface, Wiser 1

Here is what I've done to date.
- Checked each power supply (supply and bus)
- Checked overall bus power supply capacity
- Isolated individual cable lines and individual items (not all) (notably the touch screen and wiser
- isolated only external PIR I could find.
- replaced 1 dimmer and 1 relay for new (when these original items were removed from the bus the overall problems appeared to improve !)
- Checked burden and TClock - they are located and active in RS232 interface ( not at address 001 !!!)
- Have run Software diagnostic utility but not been able to witness the fault while running !

The problem is still there couple of hours after we leave and it all kicks of again
Any ideas most welcome

A

 

Also have taken the time to get hold of a scope - I can see the timeclock in operation !
May this be of some use?

 

Its an old installation that apparently has been ok for some years.
I did think of looped cable but not checked what would the symptoms of this be !

 

We have experienced installs where by LV 12V drivers have caused mains borne interference on the bus !!! YES TRUE - Schneider paid us to change the drivers! Could it be that the property has noisy mains?

 

System locking up as you describe it I would start to think loss of clock or Power supply issues.
Cheap easy idea take the clock and burden off the PCI and have them elsewhere 001 relay or dimmer.
Make sure you have 3 clocks enabled only one will be active
Power supplies a little more effort check the voltage open circuit, search the forum lots of good info on PSU fault finding.
May need to have a laptop on site
If possible run a log to see if it is a C-bus command causing the issue and from where it.

 

Wonkey
Thanks for reply - lots ofthings in post that have been done but too numerous to mention....

Power supplies have done all check ref to ground and isolating with burden and clock only in interface.
So ruled this out.

I have only 2 clocks enabled ! surely both cannot go faulty... I will add another
Q - If i isolate a power supply remove burden and leave a time clock active - when I rmove the interface with the burden in should the CBUS led flash in line with the clock ?

Only option is to try and get a laptop set up monitoring as you suggest.

 

Flashing C-Bus LED indicates low voltage.
Which you could expect if you remove PSU, as you probably won't have enough current for the network.
Removing the interface may cause the C-Bus LED to go out if it was providing the clock.
But a few seconds later when another unit takes over clock duties it should be on.
Are you sure that the change happened when you unplugged the interface not the PSU as that doesn't seem right based on my above comments.
Sorry for not replying sooner as away at the moment.

 

OK been to site again since
We now have three time clocks active
I have removed the RS232 interface
Attached diagnostic utility result (all perfect!).

The problem...... is that randomly (mostly at night) all of the channels of a 12ch relay come on - possibly other dimmer/relay channel as well (but not ALL).

We replaced a dimmer and a 12 ch relay both with power supplies - the first dimmer unit did show signs of being on its way out and the situation did appear to improve after it was replaced. The customer then purchased a new 12 ch relay as he seemed certain that this was the remaining cause of the lingering problems - not the case.

Next move is to break down the cable runs to the switches - one arm has already been isolated as it as the old (Comfort style) b&w touch screen on and this was the first thing I thought may be causing problems!

Customer is V accommodating and next step after this would be to setup a PC and monitor - HOWEVER I'm a bit worried that this is going to store masses of info and wont really tell us the cause of the problem - is any body able to enlighten us as to what to look out for and what to set up etc etc.

Any other ideas most welcome !

 

All channel going on or off on one or more devices can often be caused by intermittent triggering of the remote on or off wires. Even a small amount of moisture or dirt ingress (or rodents) can trigger these, paticularly if they are left floating (which occurs often as they frequently not connected at switches etc). Try isolating the remote on/off at the relay and see what happens. In my opinion you are much better leaving them disconnected as they are never used and just a source of problems.

 

Ashley
Thanks for reply
Already isolated green and brown pairs on switch arms..
Ill recheck
Any thoughts or comments on monitoring ?

 

Monitor the network and ask the customer to note the time of the event, then you will be able to confirm if it's a C-Bus command and where it's generated from.
Also have a look at traffic analyser in the utility software.

 

In conclusion

The problem intensified to a point where it was worth attending site again as I had somethin positive to work with (from a diagnostics point of view !).

Basically I was ale to remove CBUS components and still see the fault occurring

I narrowed it down to a single CBUS dimmer and disconnected this from the bus.

All problems on the connected bus side disappeared and while I was explaining to the customer my findings the dimmer that I had totally isolated from the bus had the lighting channels suddenly come on !!!

Replaced dimmer with a second had unit ( as NO WAY should anybody use the new dimmer and Spacelogic software its a mess ! ) and its all ben fine ever since !