Burying Cable

Hi,

Next month Im planning (in conjunction with my patio work) to fit recessed LED lights into the actual patio slabs.

From previous posts Ive got the wiring worked out but now I need to

think about what happens to the electrical cable that feeds the lights once it comes out of the house and needs to go underground.

The fittings that I plan to use allow 3 fittings to be wired in series. Im using 6 fittings so I need two feeds. My plan was to run 2 x 1.5mm SWA out of a hole in the wall of the house and then down the wall in some conduit.

Speaking to a mate of mine reservations were raised about whether this would be possible. I gather that SWA isnt very flexible and I may have trouble bending it around in the condiut box the required 90 degrees to run down the wall.

He also mentioned glands. I plan to fit a conduit box to the exterior wall with a hole in the back for the cable to run into the house. So basically, one conduit box on the wall with approx. 1 meter of conduit going down the wall into the ground. Where would I need to fit glands?

Any other thoughts on if Ive got the right idea here?

Cheers,

CM.

Reply to
Charles Middleton
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On 17 Sep 2005 07:03:08 -0700, "Charles Middleton" scrawled:

No need for the conduit, just run thew SWA down the wall or run singles or other cables in conduit, no need to go OTT.

Quite right, you've not got a prayer of getting SWA through conduit and around corners.

On the ends of the cable. Run the cable up the exterior wall, terminate into a galv end box and run from the back of their into the house.

Well, I've seen worse ideas. I take it these lights are low voltage then? If the transformer's going in the house and only the SELV supply is going outside then I'd not use SWA, OTT again.

Reply to
Lurch

Thats the question - there are two options on the lights: Low Voltage with a transformer where I can run them all in series and as you say put the transformer in the house. The option is mains powered, three in series at a time and costly messing around with SWA.

I think for the convenience and what you have said above its a transformer in the house job and then presume standard 1.5mm twin (or twin and earth). Ill probably use condiut down the wall to keep it tidy.

Cheers,

CM.

Reply to
Charles Middleton

On 18 Sep 2005 11:20:57 -0700, "Charles Middleton" scrawled:

This series thing is worrying me. What exactly is wired in series?

Probably easiest, just use PVC rigid and\or flexible tube to run the LV cables in. Try and keep the runs short and you might want to use a slightly bigge rcable for volt drop on the SELV side, something like

4mm.
Reply to
Lurch

Im possibly using the wrong terminology. What I mean is the cable loops in and out of each fitting. So you connect from transformer to fitting

1, 1 to 2, 2 to 3 and so on. Take a look at:
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Probably easiest, just use PVC rigid and\or flexible tube to run the

Will bare that in mind cheers.

CM.

Reply to
Charles Middleton

On 18 Sep 2005 13:56:44 -0700, "Charles Middleton" scrawled:

Reply to
Lurch

You don't need 4mm cable. LED lights take very little current.

What will determine the cable is the size of the glands as you need to use round flex to get a seal.

I suggest some of the low temperature stuff that they use for fountains, etc. is the correct stuff. Run it through some old hosepipe so you can repair it without taking the slabs up.

Reply to
dennis

On Sat, 24 Sep 2005 12:37:27 GMT, "dennis@home" scrawled:

Quite right, as I said use something bigger.

But they also take very little voltage, which fades away rapidly on long lengths of small cable.

Er, no. The cable will determine the size of the glands to buy to fit the cable.

Low temperature stuff??

Hosepipes are for watering gardens and washing cars.

Although this is uk.d-i-y it doesn't mean that everything has to be bodged together.

Reply to
Lurch

Waste of money and difficult to work with. Anyway the product data sheet states 1mm and thats for >20 units

The initial voltage doesn't matter they will drop by the same percentage.

The fittings come with glands.

The rubber stuff which stays flexible when cold (unlike PVC).

So pay 20 times as much for some flexible conduit which offers no better protection if you want. He could bury the stuff without the hose if he wanted, it doesn't need protection at such a low voltage.

Anyway using available materials isn't a bodge its engineering. There used to be a time when some trades people could actually do things without having to follow a table of instructions like they do now.

Reply to
dennis

Not according to Ohm's Law.

The stuff I have itsn't rubber; it's just another form of plastic.

Reply to
Bob Eager

On Sat, 24 Sep 2005 16:13:55 GMT, "dennis@home" scrawled:

But the product data sheet doesn't know how much volt drop is in the circuit so is basically just a number.

Er, well. Either way, volt drop is more noticable on SELV lighting than 230V hence the larger cables needed for SELV.

Then get different glands to suit. You don't size cables according to how big the glands that you happen to have are.

Rubber? Don't think they make that anymore. Doesn't need to be that anyway, the wiring is staying where it is so no need for it to be flexible.

It does actually as hosepipe offers no protection.

Think you'll find it does.

No, definitely a bodge as it's using incorrect materials.

Right, but things weren't bodged and rules were followed. I agree, there are plenty of rules about, many of which are ridiculous.

Reply to
Lurch

But LED lamps are low current.

The nine LEDs will be in series and only take about 0.2A. The recommended 1mm cable is OK upto 20m with>20 units on it.

You haven't seen some of the patios and wood decking that is around.

Niether does plastic conduit especially the flexible stuff. Steel conduit would rust and be useless after a few years.

The hose was there to make it easy to replace the cable if needed.

As is using 4+mm cable.

Reply to
dennis

On Sat, 24 Sep 2005 18:23:41 GMT, "dennis@home" scrawled:

You seem to have this thing about current, the volts still drop whether it's LAD or halogen lighting.

Depends what flexible conduit you use.

How is using a larger than required cable (your words) classed as a bodge?

Reply to
Lurch

There is zero volts drop if you don't have any current. Basic physics.

Reply to
dennis

But the lower the current, the smaller the voltage drop.

Reply to
Rob Morley

And LED lights have low currents. So you don't need thick cable.

Reply to
dennis

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