Outdoor Lighting and Summer House Supply

[llcooldl]

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

 

[rick.oshea]

Andy,

A few concerns mate ..... firstly, just to let you know its all notifiable work.

All the sockets need to be protected by and RCD (17th Ed)

Your cable size needs to be calc'ed from your max demand (after diversity) and at 100m, you are going to struggle with too big a voltage drop on 1.5mm2.

The length of cable in the ELV circuit is also going to cause you concerns with Vd

Your fused spur will only supply 13A......you would normally be better to run a dedicated supply off the tails through a dedicated rcd and then down....

A 200m ring extention is def not the way to go...

If an earth fault occurs in the house, this will be introduced to the out buildings and is better to install a TT spike and run a separate earth.......

If you are starting out and are newly qualified, you may want to seek some additional help from a local spark on this one buddy....

Hope this helps..

 

[Dunc]

Andy,

A few concerns mate ..... firstly, just to let you know its all notifiable work.

All the sockets need to be protected by and RCD (17th Ed)

Your cable size needs to be calc'ed from your max demand (after diversity) and at 100m, you are going to struggle with too big a voltage drop on 1.5mm2.

The length of cable in the ELV circuit is also going to cause you concerns with Vd

Your fused spur will only supply 13A......you would normally be better to run a dedicated supply off the tails through a dedicated rcd and then down....

A 200m ring extention is def not the way to go...

If an earth fault occurs in the house, this will be introduced to the out buildings and is better to install a TT spike and run a separate earth.......

If you are starting out and are newly qualified, you may want to seek some additional help from a local spark on this one buddy....

Hope this helps..

Agree with some of the above, the main thing is the OP is talking in feet with everything so the supply to the end of the garden will be 40m ish rather then the 100m you originally thought Rick

I would suggest getting a spark in though as this job isn't a straight forward one and unfortunately for yourself being an electrician isn't hereditary. I would also think that running a separate supply to the end of the garden from the consumer unit would be a better idea but i don't know how practical this would be as i don't know how your house is laid out.

 

[yellowvanman]

For remote switching of outdoor lights try these:

Welcome to Luminite Electronics Ltd

Agree with other comments best get a qualified sparky.

 

[llcooldl]

Thanks for the replies so far!

I will not be doing this myself! I know "sparky" is not an inhertited gene, dad has just had a stroke in his communication centre so is unable to do the work / advise plus he retired 10 years ago anyhow! (London Liverpool St was his handy work The life of my three kids, wife and myself is worth far more than a few hundred quid to pay a sparky to do it properly!

I really should have pointed out that at the moment my garden is a blank canvas. I am redoing the drive and front and back gardens, buying the summer house, building brick walls etc and that part I am doing myself, it will take me about 6 weeks. I will be getting a sparky to do the electrics IF I can afford to do what needs to be done, otherwise I won't be having electric in my garden!

At this stage all I really want to do is understand what needs to be done so that I can at least lay the armoured cable (unconnected at both ends!) in the right location before laying the patio / driveway / pathways as the cable is going to run underneath these! This way I can get a sparky in a few months time to do the rest of the work.

I know the depth needs to be at least 450 mm (some say 600mm?) and identification tape needs to be burried at 150 mm and I need a detailed drawing plan (I have drawn my house and garden in 3D on CAD to scale and will put underground cables on this once I know where they are), before anyone says it the cable will be run along the property boundary.

Getting to the main consumer unit is not a problem as the drive will be up for a short while and I plan to lay the cable then. As I said in my original post there is no spare capacity on the current consumer unit to add a dedicated ring main for the garden which is ideally what I would want to do.

So two remaining questions...

Will the outdoor circuit HAVE to connect to the main consumer unit? (I do only need 13 Amp!)

What core thickness armoured cable do I need? (If not 2.5mm does anyone want 100 m ???

many thanks
Andy

 

[llcooldl]

For remote switching of outdoor lights try these:

Welcome to Luminite Electronics Ltd

Agree with other comments best get a qualified sparky.

I never knew such a thing existed that's great! Thanks!

 

[rick.oshea]

Agree with some of the above, the main thing is the OP is talking in feet with everything so the supply to the end of the garden will be 40m ish rather then the 100m you originally thought Rick

I would suggest getting a spark in though as this job isn't a straight forward one and unfortunately for yourself being an electrician isn't hereditary. I would also think that running a separate supply to the end of the garden from the consumer unit would be a better idea but i don't know how practical this would be as i don't know how your house is laid out.

Cheers Dunc.... my eyes were shutting while writing and my brain had obviously already taken itself to bed

The misus keeps complaining when I estimate sizes as well...?

 

[PC Electrics]

This thread just has to be a wind up! The very idea of extending a ring by an extra 60m in swa just boggles the mind.

I really do feel like I've wasted 3 minutes of my life on this.

 

[llcooldl]

This thread just has to be a wind up! The very idea of extending a ring by an extra 60m in swa just boggles the mind.

I really do feel like I've wasted 3 minutes of my life on this.

Thanks Mr PC! That most certainly answers the question about having to get a new main CU!

Next can anyone tell me the correct core SWA that will be needed?

 

[pushrod]

Split the tails with henley blocks to a switch fuse unit then swa to summer house, then small rcd CU for circuits. Need to calculate Vd carefully. Would be the way i would go.

edit :unless you want/need to replace main CU

 

[malcolmsanford]

Here should endeth the advice ................just say the once ..............if your on speaking terms with dad he'll sort it out, if your not then a competant electrician will.

 

[Chr!s]

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

What wattage?, low voltage high current

 

[llcooldl]

Thanks Pushrod, that certainly sounds like a cheaper option (assuming it's safe!)

I've already calculated the voltage drop. Presuming everything I will have plugged in down that end is all turned on at once (you never know when you might want to mow the lawn in the dark!) the the total wattage is only 2,500W!, making it safe I calculated using 4,000W. Which is just shy of 17 Amps. So being the over careful sort I am based on a 30 Amp pull, the VD across a 2.5mm cable for a 200 foot circuit (there and back) is only 7.2 Volts!

Surely a 2.5mm cable is safe?!

 

[llcooldl]

what wattage?, low voltage high current

0.12 w

 

[llcooldl]

Here should endeth the advice ................just say the once ..............if your on speaking terms with dad he'll sort it out, if your not then a competant electrician will.

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

 

[malcolmsanford]

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]

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]

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]

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]

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]

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.

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]

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]

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]

One length mate.

 

[Engineer54]

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]

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]

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]

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]

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!