Wiring to shed/outbuilding

[CortinaV8]

I've asked about this before, in passing as it was a job I was getting round to doing, but never did. Anyhow my father in law was helping out in the garden and managed to find the buried conduit i had been telling him about 5mins earlier with a spade, for now i've disconnected the outside suppy at the source.

Currently the supply to the shed is/was fed from the back of a double socket on the downstairs ringmain which isnt ideal, this runs in some buried plastic conduit to my brick shed/outbuilding, at this point it goes to a single socket then a spur from this to an FCU feeding a small striplight.

I was planning on adding a spur from a (13amp) FCU in the garage, fixing a batten to the concrete fence posts and plastic conduit to this a couple of foot off the ground away from spades etc. I was intending to use 2.5mm T&E (40m length) TLC's voltage drop calculator seems to suggest this is more than adequate.

I dont really see the point of going to the extent of fitting a small CU in the shed for the sake of a light and somewhere to plug my lawnmover/pond pump into once in a blue moon.

I apreciate I could use SWA, but its more expensive and i've got plenty of new T&E spare from a previous job, obvious I'm breaking the law by doing this work myself, but **** happens.

Just looking for any pointers or other suggestions really, does the conduit have to be a specific distance from the ground or is it just common sence?

 

[ericmark]

Twin and earth even in plastic conduit is not really tough enough to be in the garden. Even if clipped to a fence. I would use SWA every time.

As to shed consumer units yes I agree that a 13A socket with barrel nuts connecting to a FCU in most cases is enough for single socket and lights.

I have nothing against breaking the odd law or two I have let my speed drift over the limit from time to time. But one still must use some common sense and ensure that any installation is tested and is safe for all the family.

To ensure an insulation is safe then one must do all the tests required to complete a minor works cert or and insulation cert. However the equipment required is not cheap.

Do remember if you get it wrong although you may escape death you could still find yourself with a manslaughter charge if you can't prove you did all required tests and some one else gets a lethal belt.

Next time we read how some one has died due to tests not being carried out I will think of your comment.

but s**t happens

 

[CortinaV8]

How come you say T&E in plastic conduit isn't suitable, I ask because the current stuff seems to have done a good enough job for the last 20 years, its probably worth mentioning I had the house PIR'd 3 months ago and it passed with flying colours.

Perhaps I will just call my electrician and see what he says, if I do the bulk of the work I can't see it taking more than an hour or two to make the terminations and test.

 

[SparkyNinja]

How come you say T&E in plastic conduit isn't suitable

Ask the spade

 

[ericmark]

Flat twin and earth cable is designed to lie flat against a wall either surface or buried inside a house.

It was never designed for out side use. By using conduit extra protection is afforded but the nature of the twin and earth makes it very hard to draw into conduit which is designed for singles. Plastic conduit affords the same protection for singles as the outer sheaf gives to twin and earth and is designed to be used in the same sort of environment as twin and earth.

When used out side it will need to be black to resist UV rays and to put twin and earth in black conduit to protect from UV does make some sense.

However this would only be done where the cables are out of harms way as when firmly attached to a wall.

Metal conduit does offer more protection but is very rigid and if mounted to anything likely to flex like a fence could be subject to as a result.

This leaves the use of wire armoured cable. There are two main types, the black type has quite thick wires and so less likely to be severed by a spade of if damaged less likely to be damaged by rust. The SY cable is more flexible and still give protection when hit by a spade in that it will earth the spade before it cuts inner cables but easier to cut in first place and once the outer plastic is damaged is quickly damaged by rust. The transparent plastic does however give indication of such damage.

Both SWA and SY cables are normally glanded but the SY cable can be used without glands where it is hard to use the SWA cable without glands and ensure it is neither crushed or the earth to armouring is lost. There are some methods where a ring of metal is placed under the armour before a clamp is placed around it but in the main this is only done inside a cable joint which is then sealed in some way.

To use twin and earth out doors is similar to using bell wire indoors and although in both cases it may work for years without any problems it is asking for problems to happen.

Often it is not the person who does the substandard work who gets injured and because of the number of cases of injury due to substandard work the government brought in Part P. This regulation makes it much easier to prosecute where there is substandard work as no longer do they have to prove it was not fit for purpose they only need to show it was installed in a special location which includes out doors without Part P approval.

As yet I have only seem court cases where not only did the person not comply with Part P but it was also substandard. Or they said they were Part P approved when they were not.

As to a periodic inspection report this is up to the person doing the work. No qualifications are required to complete the report, you should have the skill required and professional indemnity insurance but in many cases those inspecting do miss items especially if not included in the paperwork for the installation.

514.9.1 states "a legible diagram. chart or table or equivalent form of information shall be provided indicating" and gives a list of all that should be documented. Often this is missing with domestic premises and when missing it gives the person doing the PIR a get out where they can claim they were unaware of a circuit.

Some land lords have been know to deliberately withhold information with the idea the tester can't copy information from last test report but in doing so risk items being missed and by breaking the rules nullify any claims they may have been able to have on the electricians professional indemnity insurance. That is of course if the electrician has it! It is common for electricians to rely on their public liability insurance which in some cases may cover but because they have not done any work as such and have only given a professional opinion then it may not cover.

However at the end of the day it is all up to the guy who signs the paper work and if you can get the LABC to sign off what you are doing then no problem.

If not any anything goes wrong then "s**t happens" and we will read all about it in local newspapers and trade mags.

Never quite worked out why people bother to ask advice and when given want to do anything rather than follow it? I suppose "s**t happens"!

 

[CortinaV8]

If what you are trying to suggest it that the existing outside spur was not up to standard or not tested during the PIR you would be wrong, every fitting, socket etc was checked, I pulled the place apart when I renovated it and know the locations of all the cable runs.

I ask for your reasons re: the conduit method due to the fact i've read posts from other electricians on here stating otherwise, not because i'm not interested in using SWA Cable.

Tell you what makes me laugh, people going on about testing this, testing that, yet anyone can replace a socket without the need to do any testing, it makes no sense at all to me, surely there is just as much scope for error here as there would be adding a new spur into a ringmain, which would then require testing..........

Anyhow thanks for the advice.

As to Widdler, I dont usually dig the soil over 3 foot up a garden fence.

 

[ColJack]

T+E has not metal sheath and as you found, a spade can easily go through a plastic conduit..
now if that spade had cut into the live wire only, then your spade is live..

as for testing..
if you add a spur, then you are testing that the new cable is not broken or it's insulation broken down, and that the Zs at the new point is not too high for the protection device used.

 

[ban-all-sheds]

Metal conduit does offer more protection but is very rigid and if mounted to anything likely to flex like a fence could be subject to as a result.

What about using singles in pliable conduit, such as Kopex LS1/LS2?

 

[JonoPashley]

Pretty sure your PIR will have a limitation on Hidden/inaccessible cable/joints/accessorys. Which will be why the hidden death trap in your garden passed.

 

[SparkyNinja]

As to Widdler, I dont usually dig the soil over 3 foot up a garden fence.

Wah??

 

[mikhailfaradayski]

I apreciate I could use SWA, but its more expensive and i've got plenty of new T&E spare from a previous job, obvious I'm breaking the law by doing this work myself, but s**t happens.

With a comment like that, i don't really understand why you bothered to ask in the first place. Just whack it all in however you see fit. After all, thats what you were going to do anyway...

I suppose its a least one saving grace that you don't just have a load of CAT5 cable left over from another job.

..... if i just twist a few of these cores together, will that double the cables current capacity?...