What external wiring should I use, to comply with regs?

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When I built my house four years ago, I asked the electrician to include an outside box on a separate circuit breaker so that later I could run 2.5mm2 SWA for electric gates/lights.

I'm about to build the brick pillars on the drive and I want to bury wires inside the pillars, for a couple of 12v led outdoor lamps mounted on the pillars, fed from a 20W garden lighting transformer in a box at the base where the SWA will terminate.

My main question is:

What type of wire should I bury inside the brick pillars to feed the 12V leds? 1.5mm2 12V "garden lights" cable or some kind of mains cable? I'm slightly concerned that when I come to sell the house someone could potentially switch the leds to mains bulbs and try and run mains down the garden cable. But on the other hand, if I use mains cable for the 12V leds, what type should I use, but surely then it's wrong because the wire colours don't match the 12v use?

My secondary question is:

Even though Part P no longer requires notification for outside electrics, I'll get an electrician to connect up the SWA at both ends to make sure the circuit protection is compliant, but out of interest, in the box, how would I make a compliant mains connection to the sealed 12v transformer, which I want to switch using a Light Symphony single channel lighting controller, next to it. The controller is two wire, double-insulated, with a thermal fuse, and connects between the mains and the transformer primary. Is a permanent connection ok? Thanks!
 
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Instead of burying cable in the pillars install ducts for the cables so if necessary the cables can be changed to suit if the types of lamp are changed later ( by new owner ).

It may be better to earth the electrics around the gate area to an ground rod and not export the "earth" from the house via the armour ( or a core ) of the SWA
 
Thanks bernard, ducts is a good answer. Does the type of earthing depend on the distance? It's 37m

Yes, there will be electric motors and the gate company will install those. I just wanted to get wires in now to avoid trying to drill through the pillars later, as they have large steel i-beams inside.
 
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You should also consult the gate people.

You will also need cables for the IR detector beam on each pillar.
Also you may need a call button/manual release/keypad.

All this will need to go into and on your pillar to and from the control box.
 
The photocells use 6-core alarm cable so no problem there. I was going to use a 20mm flexible corrugated conduit just for the intercom/door entry which is two cables.

Thing is, if I use a conduit for the photocell, a conduit for the intercom, two conduits for the two lights (one at front, one at back), that's four large tubes arriving at roughly the same place at the back of the pillar. Is there any alternative?
 
I built hollow pillars on concrete slabs for lights and power outlet at the bottom of my garden. This allowed for the ducts to come vertically up through the centre of the slab and the pillar was then built around the ducts.

If you are unsure about what is needed then install a large diameter duct from the pillar to a point where it's capped and buried end could be accessed to add cables or ducts later. The capped end being far enough away from the pillar that digging down to it in the future will not affect the foundations of the pillars.
 
The photocells use 6-core alarm cable so no problem there. I was going to use a 20mm flexible corrugated conduit just for the intercom/door entry which is two cables.
Good luck pulling all those cables through a long run of 20mm flexible conduit...
 
The photocells use 6-core alarm cable so no problem there. I was going to use a 20mm flexible corrugated conduit just for the intercom/door entry which is two cables.
Good luck pulling all those cables through a long run of 20mm flexible conduit...

It's ok, it would be only from the front of the pillar, somewhere near the top, to the back of the pillar, somewhere near the bottom, with a slight bend around the steel core. Less than 2m, I would think.
 
The two slabs are already done, nearly a tonne of concrete each, with steel i-beams for cores sticking up. And the brick pillars, when built, have to be filled with concrete, too, so they can't be hollow.

So ducting is a nice idea, it's just that I think I would need four (two lights, intercom, photocell). I wonder if there's a way to somehow combine them, as they all need to meet up where the control box will go. Or maybe use thinner ducting than 20mm where there's only one wire. Garden hose?
 
Where to they go after that?

All the wires go to the gate control box on the back of the gate pillar. From there, will be a trench to contain the SWA and a two-wire 1.5mm2 or 2.5mm2 12v cable for the EntryVue video intercom bus. This goes to an existing wired box outside the house put there for this purpose.
 

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