Control Stage Wiring

Just wondering how people are wiring control stage mains feeds?

As I understand it to prevent the dimmer dropping off the Cbus network these should be wired seperately to the main dimmer stage and should not be connected to the mcb protecting the main stage.

Are people wiring them to a seperate mcb with several dimmer control stages wired to a single mcb? If so what rating should this mcb have?

Thanks
Mick

 

Well Relay

The reqirement to have the two mains connections wired in to a C-bus DIN dimmer on seperate circuits is only realy needed in comercial installations where some form odf generator or UPS back up is used and it is required to keep the bus powered but may be not all of the controlled circuits. This can then be used to seperate those controlled circuits that are deemed 'esential' and those that are not. In domestic installations (assuming there is no back up generator) it would normal to loop the mains from the supply to the output channels over to the units mains input to the power supply.

As far as circuit protection we must be aware that what is required in some countries is not necessary in others and reference to the local wiring regulations should be made before following any advice shown on this or any other product forum. Often there is no clue as to where the original enquiry comes from or where any of the reponses originate either and as C-bus is sold in many countries other than Australia please bear this in mind when writting or acting on suggestions.

In a way having 4 or 8 dimmers in a DIN package is electricaly pretty much the same as having 4 or 8 individual dimmers spead around a house, now in Australia the wiring regs (and I am no sparky so feel free to correct me if I'm wrong) allow for all of those dimmer circuits to run on a single lighting circuit normally protected by an 8A or 10A MCB (or fuse). The purpose of MCB's in the wiring regulations is to provide protection to the wiring not necessarily any products hanging of that wiring (ie you could have a TV connected to a power circuit that in Australia would normally be protected by a 16A or 20A MCB. That TV could have a fault dissipating 5A, plenty enough power there to start a fire, but not enough to trip the MCB).

I guess what you are asking is will an 8A MCB on the power feed to the output channels of a C-bus dimmer protect the dimmer channel in the case of a s/c on the load side of one of the channels, test done by the manufacturer suggest that it will but this may not be a 100% gaurentee as there may be uncontroled variables such a line voltage and source impedence PCB track thickness, terminal resistance and TRIAC manufaturing tolerence etc that could effect the outcome. putting a MCB of a lower rating on individual output side channels may provide better protection but concider if the fault is a dead short how much longer will current flow if a circuit is protected by an 8A MCB rather than a 2A MCB? The MCB cannot limit the size of the current that flows only the duration. Of course if the current flow increases over a period of time the 2A MCB will trip before the 8A item but most s/c tend to be of the sudden variety.

Not sure if that has answered your question but perhaps it will prompt concidered advice from forum members who actually install the stuff


Also have a look at this thread

http://www.cbusforums.com/forums/showthread.php?t=745

 

Thanks for the response I must admit I hadn't considered the need to split loads for standby generators.

I have already created lots of discusson on the protection of outputs and have decided on a method for that which suits me and that I can justify to my clients

This particular install isn't commercial but like many I get involved in there will be a standby generator (an Irish winter night with no leccy is miserable!).

So in the case where there is a need to wire the Control Stage seperately what sort of rating of MCB should I be using and is it ok to wire multiple control stages to a single MCB?

I guess what I am asking is what is the control stage rated at for protection purposes.

Thanks