laying cable for driveway lights

[DeadBeat]

im in the process of re laying a drive way, its about 8m long and i would like to put in place 2 or three driveway lights down the side of the drive and maybe one light on the post at the end of the drive. however, im unsure how to safely do this. ill get a sparky to properly sign it off but how would you install it if you were doing it? would the cable have to come up from the ground to where the light will be and loop back down to wire the lights in series or is it more complicated than that. id like to use proper lights as opposed to low voltage stuff.

also im going to be cementing in some kerb stones, could i put the wire in a casing under that where it would bw protected or better have it away from the concrete down in the clay?

thanks

 

[PrenticeBoyofDerry]

Ideally I would recommend that you firstly get a competent electrician on board, and discuss your project with them, as they will need to see that the correct cable and the correct methods of laying the cable has been used.

You will need to calculate the cable current carrying capacity, this would depend on load requirements, distance in length of cable and the method installed.

There are no distances of the depth they must be buried, given in the regulations. But they must be reasonable to prevent damage and consideration given to ground movement.

Rule of thumb would suggest a distance of at 600mm in an area that could be tooled such as a garden, where the surface above is not to be tooled many settle for no less than 400mm. I would personally run the cable in ducts and use SWA (steel wired armoured cable). Bed the route in sand and place a warning tape above the duct to indicate a live electrical cable is benneth.

I would also draw plans/diagram of the cable route.
Looping between lights is fine.

 

[ban-all-sheds]

You must also choose your lights before any cables can be installed.

Many cannot accommodate 1, let alone 2, SWA glands, so that will need to be taken into account.

Get the lights, get an electrician, and let her tell you what to do, and supervise it. She won't be able to sign the EIC unless she does the design, construction, inspection and testing, and if it's a new circuit she won't be able to self-certify compliance with the Building Regulations.

As long as she directs and supervises she can let you do the donkey-work of digging trenches etc.

[ASIDE] Why do we say things like that? Donkeys are useless at digging trenches. [/ASIDE]

would the cable have to come up from the ground to where the light will be and loop back down to wire the lights in series

The lights would be wired in parallel.

id like to use proper lights as opposed to low voltage stuff.

1) //www.diynot.com/wiki/Electrics:Voltage-Bands

2) Light is light, and the stuff from ELV is as good as that from LV. Although if you're using incandescent lighting LV would be better as you'd need a thinner cable.


Use a duct large enough to take a 2nd cable in case you ever want electric gates, and install a 2nd duct alongside it to take other cables if you ever want an intercom, camera etc.

 

[ericmark]

id like to use proper lights as opposed to low voltage stuff.

Since 230 vac is low voltage not sure what you mean? The proper lamps use transformers wired with the primary in series the idea being the same current will go through each transformer however long the run is so each lamp will be the same brightness. This is the way to light mile long drives or runways which I am sure is not required.

So I would assume you there for want extra low voltage which instead of using a transformer in series use voltage droppers in parallel which use a switch mode method to adjust the voltage to compensate for volt drop.

To be frank at 8 meters neither method is required and by using low voltage (230 vac) LED lamps these have a built in compensation anyway.

Heat is the biggest problem with lights outside. Unless left on 24/7 each time they are switched off they will suck in any moisture as the air inside cools and contracts so the cooler the lamp the better and also don't leave any air filled voids even if only filled with petroleum jelly it will reduce the amount of water drawn in.

With LED the wattage required is low so you can have the voltage dropper in the dry with a relatively long extra low voltage supply clearly running along the drive line you will know where the cable runs and it will not be in much danger from the spade so can use cheaper cable than would be required with low voltage. With LED also DC so RF from cable is not a problem.

There is now a provision for electricians to sign off other peoples work in the building regulations but this has not been taken up by the major scheme providers neither is it endorsed by the IET/BSi regulations which require the person who is responsible signs for design, installation and inspection and testing.

So if you want it done following regulations then step one is get an electrician who then can supervise the work telling you what you should do and where he feels it's appropriate doing those bits himself. As he is in control he can then sign. However I know my son agreed to do this once and it caused him such a problem with broken promises specially on when something would be done ready for next stage he decided never again. Unfortunately this is common so finding an electrician who will supervise the work is rather hard.

So likely best option is extra low voltage if you want to DIY. In the main the extra low voltage or low voltage selection is as much to do with the market and often the best looking lamps for your drive will only be available in either or not both so may be better to select the lamps you want first then return to installation method.

 

[ericmark]

would the cable have to come up from the ground to where the light will be and loop back down to wire the lights in series

The lights would be wired in parallel.

On the air port jobs I have been on the transformers for the lights are wired in series not parallel to ensure all lights are the same brightness. But it is the special transformers wired in series not the lamps themselves and a 8 meter drive is hardly long enough to use runway lights on unless using model planes or something.

So in real terms an 8 meter drive way will have the wiring in parallel not series but with an 800 meter drive then series may be an option, however once you have seen the price of the special transformers you likely would change your mind.

 

[bernardgreen]

The other advantage of series fed current transformers supplying lamps is that a transformer that fails as short circuit turns can be tolerated ( the rest of the lights stay on ) without the need for local fuses.

 

[winston1]

With transformers in series if a lamp fails, it's transformer will see no load which will be reflected to the primary by mutual inductance. So the primary will appear high impedance and drop most of the supply voltage leaving the rest under powered.
Is my thinking correct?

 

[DeadBeat]

thanks for the input guys, really im just trying to get a handle on what should be needed and what im looking for when speaking to a sparky. and also making sure i dont get too far down the road with the driveway and its too late to put something in place.

the house is a semi, so unlikely to want too much in the way of electric gates and stuff, but i agree putting in something would be worthwhile. what kind of tubing can i put in place for future use, drain pipe or plastic plumbing pipe, something like that?

what i meant by proper lights is, i dont want some pre made led system where im running wires across the garden and they only last 5 mins, i want individual lights that wire up to the circuit and are nice and bright. low cost would be nice for running too, so im not against LED at all, just the argos garden lights etc.

I have a sparky who will be coming to make sure i do it correctly, but he is out of the country a few weeks so wanted to make sure im going down the right lines before he turns up

 

[PrenticeBoyofDerry]

A coiled duct might be worth considering, restrict the number of bends and you can always leave some drawstrings within duct to help assist with draw in any additional cables through. For what you are doing 100mm dia should be ample.

 

[bernardgreen]

Is my thinking correct?

For the average transformer yes.
for transformers designed for series connection no

For series connected transformers with out a load the primary changes to be more like a very low value wire wound resistor than an inductive load.

This is achieved by careful design of core and coils and I never did get my head round it. It is also used in distributing audio to multiple outlets.

 

[winston1]

Is my thinking correct?

For the average transformer yes.
for transformers designed for series connection no

For series connected transformers with out a load the primary changes to be more like a very low value wire wound resistor than an inductive load.

This is achieved by careful design of core and coils and I never did get my head round it. It is also used in distributing audio to multiple outlets.

Interesting. However audio distribution I have had anything to do with used about 1volt level with parallel transformers at each speaker outlet with switched taps to change the volume. Redifusion used to distribute this eay.

 

[westie101]

How to make a mountain out of a molehill in one easy move

Probably all the OP wants to do is fit/have fitted a few of these on his short 8m driveway
http://www.amazon.co.uk/Traditional...qid=1405607746&sr=1-13&keywords=garden+lights

All they need is a suitable sized SWA looped between metal or plastic boxes at the base of each to allow for glanding either placed in duct or laid direct.
(and for a route length of say 12m and a load of 9W there is little doubt on the size without going into the fine detail of calculating volt drop etc)

Then he can fit some suitable 3W LED bulbs to them and control them from a suitable switch, photo cell or timer (or purchase lamps with built in photo-cells.


Like this, with matching wall lights

 

[ban-all-sheds]

A coiled duct might be worth considering, restrict the number of bends and you can always leave some drawstrings within duct to help assist with draw in any additional cables through. For what you are doing 100mm dia should be ample.

DB - this sort of product:

http://www.drainageonline.co.uk/Ducting/Black-Twinwall-Duct-x-50m-coil.htm

IMO 100mm would be overkill. Remember you can't put phone/data/CCTV cables in the same duct as the electrical one(s), so there's a limit to how many services you'd ever want to get in.

 

[sparkwright]

The best way to lay armoured cable for garden lights is use a continous length of cable, and leave loops at each position.

This will give you scope for any alterations during the cable laying stage.

If you are making concrete bases for the lights to fix to, make sure the cable is in the concrete and vertically as possible, and the cable bends to the horizontal position below the concrete.

This way you are less likely to damage the cable if you are drilling holes for fixings for the lights.

 

[DeadBeat]

thanks guys, i replied to this but its gone missing!

ok so a few different suggestions, if i put down armoured cable would something like this be what im looking for ? if i was putting four lights on the cable only which side would you go for bear in mind, im onlu lighing up a 3m x 8m driveway not anything huge

http://www.toolstation.com/shop/Electrical/Cable/SWA Single Phase Armoured Cable/d190/sd2730/p88246

can i use this kind of conduit outside?

http://www.toolstation.com/shop/Ele...duit+25mm+x+50m+Coil+Black/d190/sd2743/p47607

thanks