Running CBUSv2 on CAT3 cable

I have a 1996 CBus installation with CAT3 cabling which was the recommended cabling at the time. I've had a few C7 related failures over the years, and Clipsal have been good enough to replace these failed units, but with CBusv2 units.

I've had all sorts of trouble getting these CBusv2 units to coexist with the CBusv1 and CAT3 installation. The network does not scan consistently, keypads sometimes need to be pressed twice. I've had to install extra burden on the network to even get it working to this point. Restoration after power failures is a disaster. As soon as I remove the 2 CBusv2 units, everything returns to normal and all these 'introduced' problems go away!

My understanding is that CBusv2 is less tolerant/more demanding of CAT3 cabling, and I am concerned there may not be an easy solution to my predicament. Ripping the cabling in a whole house is clearly not an option.

Have other people had experience of CBusv2 on CAT3, or coexisting with older installs?

What other options do I have please?

 

C-Bus V2 on Cat3

Hi,

You mention the keyswitches often take a couple of presses to get them to function. When they are pressed, do they sometimes turn on the load, and the LED on the switch a couple of seconds later. I had a similar problem a few years ago, and found the new V2 gear is less tolerent on impedence. In that situation the only fix was to install a network bridge.

Hope it comes good for you.

 

The Cat3 cable is not the issue. Cat5 is no better/ worse form the point of view of C-Bus signalling. Re-cabling would be a complete waste of time unless it uncovers things like melted insulation against plumbing (I've seen this cause the same symptoms you are observing) or intermittents, etc.

If I could, I would whack an oscilloscope on your bus and observe the waveforms, but am probably not close enough to you to help out there.

It might be possible that the system voltage is being brought down by the V2 units to below 15V somewhere in your system. Have you checked that this is not the problem?

There are a few small changes in the V2 hardware with regard to the bus interface, but they should not make comms worse. They should make it better

 

Agree Don as long as we are talking about Unshielded Twisted Pair (UTP) cat 3 but if it is not UTP then there is a big difference betwixt CAt 5 UTP and non UTP Cat 3 as far as noise imunity is concerned - and that may explain poor comms disrupting scans and conmmands etc but it wouldn't explain why it would be different between 'old' and 'new' C-bus. In addition there have been a number of sites where wholesale change over of products has occurred or where existing C-bus installations have had 'new' C-bus products added in as part of extensions etc and I don't recall any major issues. But in this particular instance, I recall that there is an issue with running DIN units on a system that is using the hardware burdon that is on the old 5100PC PCI - so first up Mr Halford what PCI and Burdon are you using?

 

My house is currently a mix of old c-bus gear and the new cbus-2 units.
I would have to say maybe 70% old cbus and 30% new cbus-2.
Cant say I have too many problems with both talking to each other.


My whole house is cabled in 2pr telephone cable and have had no real problems at all.

I think i would be checking voltages and burdens to see if any are out of spec.


Jason.

 

Thanks for the replies everyone. I have four cBusv2 units on the network: a PCI, a relay unit, and 2 keypads. Everything else is cBusv1 (circa1996).

The voltages readouts on these 4 units (which are spread around the house) all show 36V - no problems here.

The CAT3 cable is std phone twisted pair.

To get the system 'working' I've had to add extra burden on the relay switch - so 2*burdens on the network.

 

I have to configure 2 burdens on the network to get it partially 'working'. There is clearly something wrong here.

The cBusv2 units appear to have slightly different impendance characteristics to the v1 units. If I remove the v2 units, the network works fine.

At this point I appear to have a few options:

1) replace the v2 units with v1. This would provide a quick fix and I'm fairly sure would work. Added benefit is that the relay units would have compatible wiring. Not sure if anyone knows where I can source v1 units? Happy to swap for brand new v2 units! No c7 duds please!

2) Try to improve the existing CAT3 wiring. Whilst it works fine for v1 units, it appears marginal for v2. I'm not sure where I should start with this, and I'd prefer not to spend alot of time on a wiring 'witch-hunt'.

What approach should I take? Some suggestions already:
- try inserting a network bridge(s) - maybe this is a quick and easy way of 'cleaning-up' the CAT3 network?

- check signals at various points with an oscilliscope. What signal characteristics should I be checking for? Is there a FAQ on this? How bad does the clock have to be before its out of spec?

- are there other tools around that can be used to debug the physical characteristics of a a cBus network?

 

Just a thought ..How many cbus devices do you have...?? Is there enough devices with built in power supplies to handle everything???
Apologise if this has already been posted..

Frank

 

I don't believe there are problems with the power. Adding the v2 relay unit adds additional power over and above the v1 power supplies already on the network.

 

The network burdon effectivly sets an 'electrical envelope' that C-bus will work in that should cater for a small network on a short length of UTP to a 100unit network on 1km of UTP and all points inbetween. occasionaly you may find that a largeish network (say 60+ units) will work ok with no burden and that small netwoks (say <10 units) will work ok with two burdons. On some occasions I have seen two burdens used to effectivly clean up a network that had a lot of mains electrical interference on it ( the burden is also a reasonable 50Hz filter). Pleas confirm that the cat 3 UTP you are using has the twist maintained between the C-bus conductors ie one wire from a twisted pair should go to C-bus +ve and one to C-bus -ve and if you are parelling up two twistewd pairs then one wire from each pair should go to C-bus +ve and one from each pair to -ve. This will provide excellent common mode noise protection. To read all about C-bus wave forms etc go here:

http://www.clipsal.com/cis/pdf_files/Advanced_C-Bus_Training_Manual_V1-0-0.pdf

This is to be found on the CIS web sit (www.clipsal.com/cis) which has lots of technical and training docs under literatue.

 

just a thought

Just a thought , have you had a network analizer on the network yet . This would at least check and rule or confirm problems like supply voltage and burden issues.

 

Do you mean the C-Bus Diagnostic Software? I thought this needed a v2 network to run all the diagnostics.

 

Elaboration

Could you please tell me the exact list of CBusV1 products that work on your project.
Also, inform me about the type of the 2 keypads you are using.
The C-Bus products (V1+V2) are installed in the same or different panel?
Awaiting for your reply...

 

No he means the 5100NA Network Analyser hardware product.

 

I have approx 52 units on the network. 4 are v2 - 2 single keypads, a PCI and a 12 relay unit.

I can send the network file via PM if you wish