Running Cbus Cable... Official Best Practices

Could some one please state what the BEST design is in terms of running CBUS Cable.

1) Is it better (if possible) to have just one long length with all the devices spread over this length (ie no branches or 3 way connections)

Some times this is achievable but may make the bus longer. Is it better to have a shorter bus and lots of branches on the bus. or a longer cable with less branches

2) Have all the power supplies at one end, Some at each end, Spread over the total length of the cable. All in the middle ??

3) Have all the higher current devices (Touch Screen) nearer the power supplies on the cable ??

4) If burden required better at end of cable ?? middle of cable ?? near the power supplies ??

When doing the Power Calculations (Using Cbus Calculator). You work out enough power to supply devices with a small margin. If a Circuit breaker trips and one output module with power supply is effected there may not be enough power on the Cbus network now to power all devices. What happens in this situation ?? Does cbus stop working ?? Do just some modules stop working ?? Is it good design practice to make sure that 1 Circuit breaker failure does not take enough power supples out to cause under power of the cbus network ?? If all circuits on same phase (for dimmer modules) is it good practice to wire the incomming power connections to the modules together on 1 seperate circuit and run the dimmers and relay load circuits on seperate circuits this way a fault on a load circuit will not trip the power supply circuit of the output module?


I am after BEST Practices if you were doing the design to optimise Cbus comunication and least interfearance.

Please add any other best practices..

 

Branches have little effect on C-Bus. This is one of the REALLY excellent features of C-Bus which most people don't appreciate enough Other systems are very painful in this regard...

In general, aim to minimise the total length of the cable, and in particular the total length from the power supplies to the end of the cable.

Have a read of http://www.clipsal.com/cis/pdf_files/CBus-Voltage-Calculation.pdf

For a small network, it makes little difference. For a large network, you should aim to spread the power supplies around the network or spread the network around the power supplies.

Yes, preferrably.

It shouldn't make much difference.

It depends on the exact circumstances. Any devices with sufficient voltage on them will continue to operate.

 

Thanks Darren.

That PDF is excellent.

 

Couple of additional poits Charlie, treat the runs of C-bus Cat 5 cable like any other Data Comms cable as far as seperation from mains conductors is concerned but where the C-bus Cat 5 HAS to come close to mains ie; in the swichboard, keep max possible distance and securly anchor cables. Note the 'Dashing Pink' colour of the Clipsal C-bus Cat 5 not only is convenient for tracing in the midst of other Cat 5's but also denotes that the outer sheath is mains rated and so meets electrical safty requirments where it enters a switchboard and may be exposed (so to speak) to single insulated mains cables.

 

Quote: "Branches have little effect on C-Bus. This is one of the REALLY excellent features of C-Bus which most people don't appreciate enough Other systems are very painful in this regard..."

So are you saying a cable layout that has Power at the ends and the middle. With a bus in the ceiling (Say linking all the occupancy sensors) with branches off this bus to all the light switches is fine.

Ie power distributed and Cable keep to minimum. I was a bit worried that all the branches may cause termination type problems thus leading to reflections and data corruption on the bus.

Why did clipsal decide to put screw terminals on all the switch plates etc ??
Why did they not go for a insulation displacement connector. Would have made termination a breeze. They also could have terminated all 8 wires to it would be easyto keep the "Master ON" "Master OFF" circuits complete when you have power supplies distributed.

Charles

 

Yes, you can have as many branches in C-Bus as you want.

There are no issues with terminations and reflections with C-Bus. This eliminates a great deal of the problems normally encountered with routing networks.

 

This is fantastic.

Now I know why I love CBUS and not Dyna something....