Separation From Mains Cable

[jphilweybr]

I am doing some additional mains and telephone wiring for a friend in her lounge.  The floor is solid, having been filled in to combat severe rising damp, and all the pipework and cabling is behind the skirting.

 

Unfortunately, this is the last chance to lay cables for a future buglar alarm without serious inroads into the decoration elsewhere. I have laid the cables (unscreened which I now realise was stupid).  I have a few days before new skirting board is fixed.  I intend to cover the mains and the burglar alarm cable with PVC capping, but the maximum separation I can achieve between the two sets will be about 30mm.  There will be three runs of about 4m each round three walls where they will run parallel.  Is there something I can still do to minimise the risk of induced AC voltage? 

 

I see from other posts that metal conduits for the alarm cables are recommended, as is a filter in the control panel.  I suppose my real question is do I have to replace the cable with screened cable, which is possible but a real fag - over 100m in total split into six!

 

The alarm cables are not powered yet, but if I do an AC voltage test across one of the conductors to a nearby ring main earth, will that tell me anything?  Obviously to be repeated with several of the conductors.

 

The control panel and sensors have not been selected, but I was leaning towards the Texecom Premium, or possibly Veritas.

 

Supplementary question - is it OK to run telephone cable alongside alarm cable?  I need to do so to get a dialling facility to the future panel - about a 5m run and then through a wall two bricks thick.

[PeterJames]

Induction is not instant, and can get worse over time. Its the magnetic field transmitted by the ac and as ac isnt constant the ac noise isnt, the magnatism can take time too. You can fit a AC noise suppressor this will remove the ac noise but not always perminantly. You can also use Ferric beads on both ends of the cable.

[Rulland]

Mains run in 'safezones' as per BS7671 I assume as well?-not by the sounds of it!.

[Oxo]

As above ACT 1313 filters. Ferric beads.

In fact go the whole hog and fit the complete panel kit from ACT. Will filter the mains, bond down the ac induction and put an Earth choke on it.

If it goes unstable after that I`d be surprised.

 

Safe Zones

 

 

[antinode]

You could also earth the spare cores at the panel end to help reduce any interference, although the segregation distances are primarily to prevent mains voltages being sent down low voltage cables if damage occurs, which is not good!

 

Or you could avoid all the hassle and fit wireless (professional wireless, not the cheap ***** from Yale/Response etc)

[james.wilson]

i love safe zones. Just where we want to put a sensor

[goncall]

too much blame for fa's on induced ac,alarm cables will run along side mains in most cases somewhere in a building,you cant help it,try to keep runs to a min,cross over at right angles etc,fit suppresion if required,

[sixwheeledbeast]

All been covered above, one additional note wouldn't bother with screened cable unless the panel manufacturer requires.

It can just act like an RF aerial anyway.

[Oxo]

i love safe zones. Just where we want to put a sensor

Exactly, mentioned this to another the other day.

 

 

too much blame for fa's on induced ac,alarm cables will run along side mains in most cases somewhere in a building,you cant help it,try to keep runs to a min,cross over at right angles etc,fit suppresion if required,

Not really, seen it destroy TS`s especially an earth fault on the RKP as well.

There are of course seevral other reasons for FA`s but induced is well known and documented.

[Rulland]

i love safe zones. Just where we want to put a sensor

Very true James, right in the corners, I've known people hit mains cables, central heating pipes, aerial cables, bt cables-all in the safe zone, who's it safe for? lol.