Outdoor Lighting and Summer House Supply

llcooldl · Mar 30, 2011

Hi All,

I'm installing outdoor lighting and electrical supply to a summer house at the bottom of a 100ft garden.

The overall load is going to be as follows:

10 low energy decking lights (up to 50 foot away from summer house / 40-70 foot from house), running from a 12V transformer.

6 Outdoor lights on the patio at the end of the garden (m.ains powered)

Standard lighting in a small shed (1 light socket) and in the summer house (2 light sockets)

And the summer house will contain a fridge freezer and stereo (two double sockets)

Will also run garden electrical equipment (lawn mower, strimmer etc.) from outdoor sockets (1 double).

I will be using SWA cable from the house to the end of the garden in the summer house.

Most probably fitting a garage consumer unit so that the lighting is off one side and the sockets off the other.

There will be a spur switched fuse at the house to be able to shut down the whole supply.

All the lighting will be on one light switch at the end of the garden (rather annoyingly as I can't work out an inexpensive way of doing it!).

All outdoor switches / sockets will be IP66 rated.

The CU in the main house has no capacity for a dedicated outdoor circuit and is RCD protected.

My concern is that this will be too much load for a spur from the main house (I planned to use a 30A junction box?

Should I extend the downstairs ring main instead of a spur (doubling the amount of SWA!) or does that make no difference?

What SWA should I use for the main run? Does it need to be more than 2.5mm? (I only ask as I have about 100m!)

All advice greatly appreciated!

Andy

P.S. If you are "qualified" to do the above work and live near Hockley in Essex please get in touch! Given my dad is a sparky I can't believe I'm having to pay someone to do the work! LOL

malcolmsanford · Mar 30, 2011

llcooldl said:
If you read the complete post you would have noticed that my father has had a stroke...

I do apologise I never saw that in your post 5 and I wish him well ....................then it is back to getting a competant sparks in.

llcooldl · Mar 30, 2011

Is it possible to buy a 16 Amp consumer unit?

Maximum load for a 30 metre run of 2.5mm cable is 17Amp.

Otherwise I have to buy 6mm armoured cable when I already have the 2.5mm!

pushrod · Mar 30, 2011

llcooldl said:
Is it possible to buy a 16 Amp consumer unit?

Maximum load for a 30 metre run of 2.5mm cable is 17Amp.

Otherwise I have to buy 6mm armoured cable when I already have the 2.5mm!

You buy a small 2 way CU, often called a garage unit, and put whatever mcbs you need in - from what i remember you saying, probs a 16A for the power and a 6A for lighting. The 2.5mm² is at least good for this unless there is some derating going on you have not mentioned. If your max load is only around 10A (2.5kW) then Vd isn't a problem for the lights either. Mind think you have made a bit of a mistake with your earlier post of 0.12W, won't get much light there

Spoon · Mar 30, 2011

When we have required a cable for a 1250A MCB we ran 2x400mm SWA cables in parellel. Cant llcoolld just run 2 2.5mm cables in parellel to the new CU if he requires to?

llcooldl · Mar 30, 2011

pushrod said:
You buy a small 2 way CU, often called a garage unit, and put whatever mcbs you need in - from what i remember you saying, probs a 16A for the power and a 6A for lighting. The 2.5mm² is at least good for this unless there is some derating going on you have not mentioned. If your max load is only around 10A (2.5kW) then Vd isn't a problem for the lights either. Mind think you have made a bit of a mistake with your earlier post of 0.12W, won't get much light there

Thanks for the comments. Yes they are indeed 0.12W, 3 x 0.12W per light, they are decorative LEDs - not for reading

This type of thing (these are cheap manure though!):

LED Ground Lights 10 x 3 White LED .12W - IP38 + Driver + cables

pushrod · Mar 30, 2011

Can't llcoolld just run 2 x 2.5mm cables in parellel to the new CU if he requires to?

He could... but he won't need to for the loads mentioned.

llcooldl said:
Thanks for the comments. Yes they are indeed 0.12W, 3 x 0.12W per light, they are decorative LEDs - not for reading

apologies - was right about there not being much light though lol

llcooldl · Mar 30, 2011

I think I'll need a torch to see them

Really daft question coming up...

If the outdoor power is going to be from main cu to a garage cu in the shed do I need to lay one length of cable or do I need to run a loop (length there and length back)????

Please remember the only thing I'm doing myself is laying the underground cable! The connection work will be done in a few
months time once I have the money!

pushrod · Mar 30, 2011

llcooldl said:
If the outdoor power is going to be from main cu to a garage cu in the shed do I need to lay one length of cable or do I need to run a loop (length there and length back)????

!

From what you have said 1 length of 2.5mm² SWA will be more than enough.

edit if you are burying, 18" is usually considered adequate and when refilling put yellow warning tape about 6" above cable.

Penance · Mar 30, 2011

One length mate.

Engineer54 · Mar 30, 2011

Are you direct burying the cable or planning to install it in a suitably sized duct/pipe?? It might be worth that little extra outlay, as if direct burying, you ''will'' need to thoroughly sift the the bed and back-fill soil of sharp stones etc!!!

timdaily · Apr 5, 2011

Thanks all for such great replies.

I also installed the similar outdoor lighting last year but could not get any result because i was not aware of the electrical supply needed. I hope this post would help others like me also.

llcooldl · Apr 5, 2011

Engineer54 said:
Are you direct burying the cable or planning to install it in a suitably sized duct/pipe?? It might be worth that little extra outlay, as if direct burying, you ''will'' need to thoroughly sift the the bed and back-fill soil of sharp stones etc!!!

Direct burrying. I wanted to cut a small section off the end to just check the diameter of the cable. I took my 10lb very sharp axe, swung over head in to the cable laying on hard ground and all I achieved was to squash it slightly. Having then used an electric hacksaw (and a lot of patience) to cut through it I noticed that where the axe had hit has had no impact on the integrity of the inner cores sheath.

The cable I have is industrial, used by British Rail.

Do I really need to go to all that trouble?

pushrod · Apr 5, 2011

llcooldl said:
Direct burrying. I wanted to cut a small section off the end to just check the diameter of the cable. I took my 10lb very sharp axe, swung over head in to the cable laying on hard ground and all I achieved was to squash it slightly. Having then used an electric hacksaw (and a lot of patience) to cut through it I noticed that where the axe had hit has had no impact on the integrity of the inner cores sheath.

The cable I have is industrial, used by British Rail.

Do I really need to go to all that trouble?

The correct way of installing an armoured cable adhering to guidance would be to dig a trench (depth dependent on the land usage) then part fill with soft sand , then loosely lay the cable(to allow for earth movement), then some sort of capping, more refill then a yellow warning tape then finish refilling. However if you are doing it in your own back garden some might say it is not unusual to cut a few corners especially as you have already proved how tough the cable is lol. What i personally would not compromise on is the yellow warning tape below the surface of the soil and i would sketch the route of the cable and put it in an envelope and tuck it in behind/beside your consumer unit so that in 20 years time it is still known about. Hope that helps

Oh and with regard to cutting the cable to measure diameter - close inspection of the outside and you will usually see the size printed on it !

Edit: however whatever you decide bear in mind that it will have to be in agreement with whoever is going to sign the certificates as any outdoor circuitry is notifiable. I suspect that most part P sparks would not have a problem with signing to 15"-!8" depth and the warning tape.

llcooldl · Apr 5, 2011

pushrod said:
The correct way of installing an armoured cable adhering to guidance would be to dig a trench (depth dependent on the land usage) then part fill with soft sand , then loosely lay the cable(to allow for earth movement), then some sort of capping, more refill then a yellow warning tape then finish refilling. However if you are doing it in your own back garden some might say it is not unusual to cut a few corners especially as you have already proved how tough the cable is lol. What i personally would not compromise on is the yellow warning tape below the surface of the soil and i would sketch the route of the cable and put it in an envelope and tuck it in behind/beside your consumer unit so that in 20 years time it is still known about. Hope that helps

Edit: however whatever you decide bear in mind that it will have to be in agreement with whoever is going to sign the certificates as any outdoor circuitry is notifiable. I suspect that most part P sparks would not have a problem with signing to 15"-!8" depth and the warning tape.

I'm going three foot down and it will be running underneath a path. It's clay soil, no stones (no really!). I have 1.5 Tonnes of sharp sand that I need rid of so I will use that to lay the cable on and then cover. I really like the idea of tucking the map behind the consumer unit! That's a great idea!