Physical separation of mains and CBUS cables

Hello
Would be grateful for a bit of advice.
Doing a retrofit install in a flat in a high rise building of poured-concrete construction. Most of the wiring will be through stud walls where I can maintain the recommended 150mm separation between Network and Mains cabling.
BUT there's one wall where I'm going to have to chase the cables into very hard concrete for a length of about 4 meters. Maintaining the recommended separation will need 2 chases and I'm not keen to do more of this than I need to.
So- my question is... (leaving aside issues of SELV/mains physical separation safety) How critical is this separation over a short distance from an interference point of view. It's in a domestic setting (which I imagine to be quite EMI un-hostile)? Do you experienced guys reckon I can get away with it?
Thanks in advance

Phil

 

Phil,

I am guessing you are referring to domestic mains cabling and C-Bus network cabling ??

From a network communications point you would have no problem with the C-Bus comms for such a situation. If you consider C-Bus cabling inside a switchboard where there are breakers, dimmers (especially) there is much - much more EMI to consider in these environments. There are forum posts hanging around about how robust C-Bus comms is, fence wire and wet string, but don't start me on that.

The minimum separation inside walls has a more important less technical reason for being in place. Once the walls are sealed back up it is not evident to the uninformed average punter what may be lurking behind.

More informed trades people might notice taps on a wall, or a light switch and start to imagine what path the pipes / cables behind might be taking. Having seen and heard of many occasions where punters and tradies have drilled a hole in a wall only the let the "water" or smoke out, it seems lots of people don't know or don't think.

So think about separation for the poor bugger who might buy your unit in the years to come and drill an innocent 5mm masonry to hang a picture.

Definitely do not put mains and C-bus cable in the same conduit, if someone was to hit this arrangement with a drill there would be a very high chance of getting 240v onto the C-Bus network.

A bigger chase with dedicated conduits side by side would mean a drill down the track would get one but probably not be able to break both at once...

A bigger chase again and a fixed gap is even better.

Even better still would be to do the job properly cut 2 x 20mm chases with the recommended separation, 2 bits of conduit then treat yourself to an extra beer at the end in the knowledge of a safe job done well.

SO DON'T

Hope this helps

 

Don't understand why this is an issue? If separation is required, separation it is. Charge out all the required extra chasing work at the hourly rate for whatever needs to be done!

 

Thanks. Looks like I'm going to have do it properly and look forward to an extra beer!

Phil

 

If you're using the C-Bus Pink Cat5 (which has a mains rated sheath) then you can run it in the same conduit, you don't have to have any seperation because the insulation is 240v rated.
The seperation you are refering to is for data networks where the insulation of the cable is not 240volt rated and of course they can be affected by EMI.

I can see what your saying Lucky555 but in that case of "what if someone does this" then really we should not run any cable through walls at all

My option for what its worth is chase the one run but make it nice and deep so that the avarge joe putting the 20mm long red plug won't go deep enough to hit any cables.

 

Not sure about the wiring rules in the UK - but I would not recommend anyone follow the above suggestions - just in case you need to run cables inside walls, masonry or stud...