Another external wiring question

[davelx]

I need some ideas on how to replace the existing cable run to my garage (which is 24 year old white PVC 2.5T&E strung on a catenary at 2.5m and running through the center of an apple tree, distance 15m).

Problem is that said apple tree makes it impossible to bury the cable as the roots prevent digging the trench. ALso the both sides of the garden have mature trees/shrubs that prevent digging a trench, and soil is solid clay with water about 12" down.

Over head is a problem too - even at 3.5m, which would require a pole on the back of the garage, the cable would still go through the tree and an overhead cable right up the centre of the garden is not acceptable.

Fences are wooden both sides and there is a 4m deep paved patio at the back of the house. Distance is 15m.

The only think I can think of is to lift the patio and bury in the lawn - which is going to need a mechanical digger cos the clay is far to heavy to dig by hand - except there there is no access to get said digger in without wrecking the rear fence, and it would ruin the lawn anyway

Ideas welcome! (I'm tempted just to replace the existing cable with hituf and plead ignorance)

 

[Maxxy]

Chuck some pictures up, someone may see an idea that you havent noticed

 

[davelx]

Chuck some pictures up, someone may see an idea that you havent noticed

Good idea, I'll do that - but will have to wait till the weekend so I can do it in daylight as the flash won't be powerful enough.


Thanks

 

[Maxxy]

Have you thought about running it along the fence? It wont look too pretty, so maybe run it a few inches down from the top, and put some kind of fancy wood covering over it. Not sure how it stands with the regs, no doubt someone will see this and fill in the blanks

 

[plugwash]

digging by hand should be possible just slow, and you should be able to use a mechanical digger without destroying the lawn if you are carefull and run the digger on wooden boards.

another alternative could be to hire a mechanical mole (of the kind they use to put pipes and cables under roads) not sure how much they cost to hire or how big the support equipment for them is though.

 

[JohnD]

Problem is that said apple tree makes it impossible to bury the cable as the roots prevent digging the trench.

I think not...

 

[davelx]

Problem is that said apple tree makes it impossible to bury the cable as the roots prevent digging the trench.

I think not...

But then I and my next door neigbour would loose our supply of bramleys for apple pie

I've tried digging in that garden by hand - the clay is almost yellow and it's backbreaking work - I'm too old for that!

 

[kevnurse]

You're probably not going to get a cheap or easy solution from any professional electrician here, which is quite understandable.

In my unqualified view, the answer is in the question. 24 years after you ran that cable through the tree its still working. Now, you cannot possibly sell your house with that arrangement, but, hey, who cares, when the time comes you simply tear it down and the leave the problem to the next guy. In the meantime you have to consider if a replacement cable running through the tree is going to be hazardous to anyone, bearing in mind the litiguous world we live in. As a regular householder I would replace the cable, run it loosely through the tree, ensure that there is a drip loop at both ends and, of course, fit an RCD. Incidentally, I would also leave it live all the time, because the micro-second a problem begins to develop, the RCD will activate, giving you both safety and the opportunity to check the dead cable when you eventually need it and find it doesn't work. If you leave it off, then it rains and the cable becomes immersed in water with a dormant fault, you don't want to be switching it on, even with an RCD. I would test the RCD periodically, of course.

Waiting for incoming.......

 

[plugwash]

is there any reg against running cables on cantenery wires through trees?

if you are going to keep it overhead then i'd at least replace the cable with something more appropriate (4mm or 6mm split con seems like a good move) and possiblly raise it up to the reccomended height.

 

[securespark]

The regs just say that every item shall be selected & erected so that is is suitable for its environment...

BT happily string dropwire through trees...

And I've seen TT supplies strung huge distances through trees too, but I'm not sure if the regs apply there....

 

[plugwash]

afaict the recs/dnos have never worked to BS7671, i belive they work to a combination of the statutory ESQCR (and possiblly also the older ESR, not sure if theese were ever actually repealed or not) and thier own internal rules.

 

[securespark]

and thier own internal rules.

[Scoff] Do they have any?! [/Scoff]

 

[davelx]

Well, I didn't run the cable - it was there when I moved in, and it's been live all the time for at least 24 years, through the hurricaine a few years ago etc with no problem at all.

As an ordinary householder, I don't have to comply with the wiring regs, of course. I just have to comply with the building regs.

So it could be argued that running the cable through the trees at 9ft up in this specific location where there is no possiblilty of anyone or anything snagging it (apart from the tree), with suitable protective devices, meets the building reg requirements. I think putting the cable higher would actually be less safe as there is more movement in the tree higer up. Where it is now, it is below the moving parts - I'll post a piccy later today.

I think maybe I'll put an RCD at the CU end of the feed, replace the catenary wire with a new one, replace the cable with hituf (or split con - how easy it that to work with, I've never used it?), put a new mini CU in the garage with 16A and 6A MCBs for power and lights and leave it at that.

Now, of course, this is notifiable work - I've not yet tried an electrics only notification with my local council, so I've no idea if they've got their act together, or if they will accept my test documentation.

Thanks for all the advice.

 

[davelx]

Here's a pic of the cable through the tree. You can jsut about make out the catenary wire.

 

[plugwash]

I think maybe I'll put an RCD at the CU end of the feed, replace the catenary wire with a new one, replace the cable with hituf (or split con - how easy it that to work with, I've never used it?),

pretty easy from what i can gather, no need for glands or anything just sleeve the earths (i've heard its often easier to use two sleeves because of the way they come out of the cable) and gather the neutrals together.