Is this normal ?

I am fixing a design for CBUS in a large mission-critical installation (99.99% uptime) and I found several omissions from the design.

I am reluctant to point fingers until I see the document which specifies who actually put the design together but since the specifier used normal CBUS and not professional CBUS I am stuck with whatever is there.

Each floor of the single occupier building has its own network. And from what I can see there is no interface and no bridges. No MCB on each modoule. No RM modules. No filters. Nothing. Just whack, stack and goodbye.

Please ... if someone wants to tell me how to get a job doing such poor work. I will lower my standards to get more work.

Just from the forums point of view what do you use in a 5 level building with absolute uptime requirements. I would have thought at least Professional.

 

You would only need a bridge if you needed interconnectivity between networks such as common loads. Otherwise you could leave them as seperate installs - much like you and your neighbour having C-bus with no bridge between the systems.

An MCB on each module is not required, as long as the entire lighting circuit has an MCB it complies, but we all know the disadvantage of that. Trip the MCB and all lights go out. A circuit breaker is recomended by Clipsal on each device so I would say tha tit is deficiet here in that respect.

Filtering - not a C-Bus requirement but good practice in bad areas.

I think you know the answers to most of your questions and I am not trying to indicate what I believe is the right way to do the job, just playing devils advocate here.

As for 99.99% uptime - this can't be achieved with C-bus. It does not support redindancy of any sort so a failure of any output unit will blow that figure out the window straight away. Power will also have to be available 99.99% of the time so I assume that a UPS is also being used on each network.

Mick

 

While this is true of the C-Bus units themselves, there's nothing stopping an installation being wired with multiple relays to ensure that the lights can always be either turned ON or turned OFF. Relays can be given the same group addressing so they work together.

Series connections can ensure that the circuit can always be turned OFF. Since relays in my experience generally fail through contact welding (stuck ON), the series connection would make more sense to me.

 

While C-Bus is theoretically a distributed system single device failures can still bring the whole system down so true redundancy is impossible. Over the last 6 months I have had 2 devices fail (a Shutter Relay and Fan controller) that took out the whole system. This is difficult and time consuming to fault find. I'm actually a bit surprised this is possible, but it's very repeatable. Plug in the device, complete system failure, disconnect device, system launches back into life.

 

I too have a dimmer that will not recover after a short power fail and it takes out the whole network and makes it unusable. (I need to get a delay make timer I think to keep that dimmer off long enough to recover properly)

Its not just the 240V side of the system that needs to be considered.

Mick

 

Please make sure that tech support knows about this and that these units are returned for investigation (Attention: Don). While I'm aware of a few cases where a unit can bring down a whole network, analysis has always revealed an intermittent component or intermmittent connection. If you have units that can bring down a system every time they are connected, we need to look at the mechanism and prevent it from happening in future.