External Electrical Cabling

[DOD]Asprilla · 22 Apr 2014 at 10:28

Morning,

I've currently got power in my garage and my shed run using armoured cabling. The cabling runs from the house to the garage and then from the garage down to the shed at the bottom of the garden.

We've had some changes to the garden and I need to change the routing, but the existing cabling isn't long enough for the new route and so I was thinking about cutting the existing cable, adding a junction box (possible for wiring lighting into a wooden playhouse at a later date) and then replacing the original cabling with a new run down the fence.

Trouble is that I don't know what I need in terms of cabling and junctions / terminations. Can anyone provide any advice?

Current cabling is marked 3x2.5mm 1600v and is approximately 15mm in diameter.

Tappits · 22 Apr 2014 at 10:39

2.5mm seems quite small for a run to an external garage. is it a very small run (5-10m) to a single 13amp socket or something.

I know on our 25m run we used 6mm.

Anyway just use an ip67/68 junction box and extend it.

Or get a professional electrician to do it for you.

[DOD]Asprilla · 22 Apr 2014 at 10:56

Total run is about 15m.

Two double sockets and two strip lights in the garage and one double socket and one strip light and one double socket in the shed.

It was in-situ when we bought the house and we've had a full electrical survey (to see if we needed a full rewire) and it was deemed to be fine. Consumer board was replaced following the survey (by a different electrician to the one that did the survey) and they were happy with the installation of the external cabling.

Mynight · 22 Apr 2014 at 16:43

Been a while since I've done any external wiring but you'd need;

SWA wire a rubber sheaf for each end and a gland (think that's the right name) at each end to connect the earth.

http://m.screwfix.com/p/prysmian-lv-armoured-6493x-3-core-cable-2-5mm-x-25m-black/38769

http://m.screwfix.com/p/bg-nexus-4-pole-junction-box/33518?_bck=1
(I assume its not being buried and mounted on a wall? Otherwise will have to be ip67 min as mentioned above)

http://m.screwfix.com/p/tower-external-gland-kit-20s-ip66-pack-of-2/25996?filtered=true&_bck=1

A decent hack saw would be very useful along with a sharp knife. If you can borrow a ratchet style cutter do it they're a bit expensive for a one off and standard cable cutters aren't man enough for swa. It can be done with a hacksaw and standard cutters but a ratchet style will make life a whole lot easier.

Should be fine. I'm pretty sure you'd need a qualified sparky to do it(legally anyway).

Hardest part is cutting the damn wire.

Easiest way to find the correct cable would be to see what size breaker its connected to on the main consumer unit.

C.R.A.Z.Y · 22 Apr 2014 at 23:00

Just make sure that the fuse/mcb protecting the SWA cable is 16A or less.
Unless you plan on running lots of high current devices in your garage than a 2.5mm radial should be sufficient, it will allow for approx 3.8kW.
It also MUST be RCD or RCBO protected, I'd also recommend using both the Armour and the spare core for CPC as this will ensure the earth bonding is solid. Belt and braces :-)

To terminate SWA all you need is a junior hacksaw (A £1 Draper poundland will suffice) and a Stanley knife, just take your time and visually inspect to make sure you haven't nicked/damaged the conductor.

Sone · 22 Apr 2014 at 23:07

Mynight said:
Been a while since I've done any external wiring but you'd need;

SWA wire a rubber sheaf for each end and a gland (think that's the right name) at each end to connect the earth.

http://m.screwfix.com/p/prysmian-lv-armoured-6493x-3-core-cable-2-5mm-x-25m-black/38769

http://m.screwfix.com/p/bg-nexus-4-pole-junction-box/33518?_bck=1
(I assume its not being buried and mounted on a wall? Otherwise will have to be ip67 min as mentioned above)

http://m.screwfix.com/p/tower-external-gland-kit-20s-ip66-pack-of-2/25996?filtered=true&_bck=1

A decent hack saw would be very useful along with a sharp knife. If you can borrow a ratchet style cutter do it they're a bit expensive for a one off and standard cable cutters aren't man enough for swa. It can be done with a hacksaw and standard cutters but a ratchet style will make life a whole lot easier.

Should be fine. I'm pretty sure you'd need a qualified sparky to do it(legally anyway).

Hardest part is cutting the damn wire.

Easiest way to find the correct cable would be to see what size breaker its connected to on the main consumer unit.

I don't do SWA but work with sparks who do loads of it. All gland using a hack saw and a stanley knife. Need 2 spanners is a real pita with adjustables. Weird size i think 24 or 26mm normally.

abbotsmike · 23 Apr 2014 at 01:19

Don't quote me on this, but I don't think you'll need a sparky to do it as you are modifying an existing circuit and sticking to the current ratings/spec.

I'd use a metal junction box. Much tougher, SWA is a bitch and I could see the glands pulling out of a polycarb box. Also makes it much easier to earth the armour!

Mynight · 23 Apr 2014 at 09:06

Your right modifying an existing circuit doesn't need a spark but there's a couple of exceptions iirc depending on the area outside/bathroom and kitchen tend to be iffy I think. Also I believe you're only allowed to do a like for like to modify if I've read the op correctly he's changing the routing and splitting the cable to two. Ill dig out my regs book and double check.

Edit:regs book is hiding but page 2 of this is pretty useful;

http://www.niceic.com/Uploads/File1247.pdf

You can use metal junction box outside? Didn't know that.

abbotsmike · 23 Apr 2014 at 10:46

I guess it depends on your interpretation of like-for-like! Excepting the talk around the playhouse, Running a longer piece of cable on a different route fits in that to my mind. It wouldn't surprise me if those in charge disagree...

RE: metal box outside, I've just scanned through the 17th ed, can't find anything, but I'm also revising so brains not quite in it. I've seen it done and don't see anything wrong with it assuming a galvanised steel box is used, which most are.

Mynight · 23 Apr 2014 at 11:05

Even with the regs its a bit of a minefield. As long as the length of cable isn't greatly increased then I personally don't see an issue. I also don't really see there being any difference between having the ability to replace a cable and altering it slightly. I mean if you've kept the same gauge and instead of wiring it in twice to the CUs you wire in an inbetween. If you're capable of one you're capable of the other.

Ill have to look into the metal boxes they've got to look better than the plastic crud. Cheers

C.R.A.Z.Y · 23 Apr 2014 at 21:50

Provided it's RCD protected and you fully test the installation once complete then you can get away without glanding the SWA.

Just use the spare 2.5mm core for the CPC and a couple of connector blocks to bond together the SWA inside a IP66 external box. (make sure you use the bottom of the box for both your entry and exit cables (mavity on your side and makes it pretty much impossible for the box to fill with water))

Provided the SWA cable is sufficiently mechanically secured before entry into the IP66 box it will then be both electrically and mechanically sound, and a damn sight quicker than glanding both cables.

I'd only recommend this method on a double insulated IP66 external box, for metal clad you really should gland to the metal fixture.

BTW) ToolStation > screwfix ;-)

http://www.toolstation.com/shop/Ele...P66+Rated+120+x+120+x+61mm/d190/sd3138/p89709

Mynight · 23 Apr 2014 at 22:11

Was the first link that popped up

wholeheartedly agree though.

I've got a local shop that only sells to sparks a whole lot cheaper.

Beer_MonsterUK · 23 Apr 2014 at 22:11

C.R.A.Z.Y said:
Provided it's RCD protected and you fully test the installation once complete then you can get away without glanding the SWA.

Just use the spare 2.5mm core for the CPC and a couple of connector blocks to bond together the SWA inside a IP66 external box. (make sure you use the bottom of the box for both your entry and exit cables (mavity on your side and makes it pretty much impossible for the box to fill with water))

Provided the SWA cable is sufficiently mechanically secured before entry into the IP66 box it will then be both electrically and mechanically sound, and a damn sight quicker than glanding both cables.

I'd only recommend this method on a double insulated IP66 external box, for metal clad you really should gland to the metal fixture.

BTW) ToolStation > screwfix

http://www.toolstation.com/shop/Ele...P66+Rated+120+x+120+x+61mm/d190/sd3138/p89709

Errr the SWA armouring is classed as a extranous conductive part and as such needs to be bonded. Gland the SWA properly using SWA glands and make sure you use the banjo's and fly leads to maintain earth contiunity.

As previously said, if the run is only 15mtr the volt drop shouldn't be an issue, make sure the protective device doesn't exceed 16amps and make sure the circuit is protected by an RCD.

Liampope · 23 Apr 2014 at 23:53

Mynight said:
Your right modifying an existing circuit doesn't need a spark but there's a couple of exceptions iirc depending on the area outside/bathroom and kitchen tend to be iffy I think. Also I believe you're only allowed to do a like for like to modify if I've read the op correctly he's changing the routing and splitting the cable to two. Ill dig out my regs book and double check.

Edit:regs book is hiding but page 2 of this is pretty useful;

http://www.niceic.com/Uploads/File1247.pdf

You can use metal junction box outside? Didn't know that.

Apart from having quite a 'you should get a NICEIC spark to do everything' spin on the truth, it's also about a year out of date. As of April 2013 the latest building regs considerably reduced what is notifiable work (in England). It is now only:

1. The installation of a new circuit
2. The replacement of a consumer unit or
3. Any addition or alteration to existing circuits in a special location

Where a special location is:

1. A room containing a bath or shower, the space surrounding a bath tap or shower head where the space extends vertically from the finished floor level to a height of 2.25M or the position of the shower head where it is attached to a wall or ceiling at a height higher than 2.25 metres from that level or horizontally where there is a bath tub or shower tray, from the edge of the bath tub or shower tray to a distance of 0.6 metres. Or where there is no bath tub or shower tray from the centre point of the shower head where it is attached to the wall or ceiling to a distance of 1.2 metres.
(which would be rather easier to describe with a diagram - lol!)

2. A room containing a swimming pool or sauna heater.

As ever though - all work has to comply with Part P - which is pretty much just that you shouldn't hurt anyone with your crap work. So all work should comply with the wiring regs and be properly inspected and tested to ensure it is safe.

So as long as OP does this by the book and tests it, all is good.

Beer_MonsterUK · 24 Apr 2014 at 07:43

I like the 'you should get a NICEIC spark to do everything' spin on the truth comment.

I'm no fan of the NICEIC, but I agree that carrying out any work in an area of increased risk should be done by someone who knows what they are doing. and any work in bathrooms, kitchens or external work certainly qualifies as this.

It very easy simply saying all work must comply with the regulations, but try giving the untrained person a copy of the 400 page BS7671 book and tell them to interpret it to make sure their work is safe is nigh on impossible.

Mynight · 24 Apr 2014 at 12:37

My bad I didn't realise it was out of date. I need to find my regs book lol. Cheers

C.R.A.Z.Y · 24 Apr 2014 at 14:15

Beer_MonsterUK said:
Errr the SWA armouring is classed as a extranous conductive part and as such needs to be bonded.

Hence why I said bond the SWA inside the Box, there are more ways to bond the SWA other than just glanding

You can also use the following to earth the SWA inside a double insulated box, but personally I feel a couple of 32A connector blocks and earth bonding cable is electrically more sound due to the increased contact.
(When you are using one of the cores as a CPC/Earth then only one end of the armour needs bonding, however I always recommend a belt & braces mind-set when dealing with electrics so would personally recommend bonding at both ends :-)

)

Plenty of ways to bond the Armour on SWA, glanding is both expensive, time consuming and difficult for people who haven't done it before. Metal clad box's I'd insist on it double insulated IP66 external box's have other quicker, easier and cheaper options that are perfectly safe and electrically sound

Mynight · 24 Apr 2014 at 14:51

I have never seen those before. How do they compare price wise with standard glands?

Would you say they're easier to work with? Any benefits over glands?

Sorry for 20 questions just love learning new ways especially if it can save me money and time

Liampope · 24 Apr 2014 at 18:20

Beer_MonsterUK said:
I like the 'you should get a NICEIC spark to do everything' spin on the truth comment.

I'm no fan of the NICEIC, but I agree that carrying out any work in an area of increased risk should be done by someone who knows what they are doing. and any work in bathrooms, kitchens or external work certainly qualifies as this.

Totally agree. In fact I think any work should be done by someone who knows what they are doing! I was surprised they relaxed the notification requirements so much - but then have-a-go DIYers who don't know what they're doing probably never knew or cared about notification in the first place, so it probably didn't make any difference in that regard. On the other hand, DIYers who have bothered to learn the law, regs, etc and know the notification requirements probably also know what they are doing with the actual work (or how to find out), so it has just made it a bit easier for those people to do work in their own homes of a good standard.

It very easy simply saying all work must comply with the regulations, but try giving the untrained person a copy of the 400 page BS7671 book and tell them to interpret it to make sure their work is safe is nigh on impossible.

That's what the OSG's for

. That and the DIYnot forum search function got me through a full rewire when I renovated my last house, including doing all the testing and filling in the EIC. Had a copy of the regs but barely needed to look at it. All above board, notified, etc. Not only got my completion cert, but they even added me to the council's 'list of approved electricians who have chosen not to register with a self certification scheme', (which I didn't know existed). Meant if I wanted to do any notifiable work I would just have to notify, do the work, inspect, test, cert, then I'd get a completion cert automatically.

So that was nice.

[DOD]Asprilla · 24 Apr 2014 at 19:45

Good god fellas. Looks like I have some reading to do.

Cheers for all all the advice. I'll plough through it when I have a moment and come back if I've got any questions.