Feeding a out building 77mtrs

[springfield]

Hi All,
Am installing a ring circuit of 5 sockets,10 x 5ft twin flourescents & 6 x 400w pir flood lights into a outbuilding used for storage. I am thinking a 10mm 3 core swa will be suitable.

The run is 77mtrs. Am going to stick a 40amp RCBO at main fuseboard and a rcd board in the outbuilding.

Is the 10mm 3 core swa cable suitable for the above loading/distance.

 

[micknew]

Best do a course on electrical installation and calculations and get qualifications required to carry out the works..
The installation would need testing and a Part P certificate.

 

[Octopus]

me thinks you'll have discrimination problems

 

[johnboy6083]

max vd = 3% of 230 = 6.9
max mV/A/m = 6.9/(77x35) = 2.56 mV/a/m(i used 35A as Ib, no diversity applied)

so 10mm is not suitable, but 25mm2 is.


whats your Ze at the main board, so we can see iof iot will meet disconnection times?

 

[johnboy6083]

me thinks you'll have discrimination problems

i agree, you will have discrimination problems. It would be better to feed the outbuilding from a BS88 fuse. that way your overload protection will discriminate.

Even if you still choose not to go with a fuse at the supplyu end, an RCBO-RCD is not advisable. The only way you will achieve true discriomination with RCD's is to use S-type. It will be much more cost effective to go with the fuse.

 

[Octopus]

i agree, you will have discrimination problems. It would be better to feed the outbuilding from a BS88 fuse. that way your overload protection will discriminate.

Even if you still choose not to go with a fuse at the supplyu end, an RCBO-RCD is not advisable. The only way you will achieve true discriomination with RCD's is to use S-type. It will be much more cost effective to go with the fuse.

I really dispair people here clearly giving all the answers to DIYers. Every time this happens you are damaging the trade.

 

[johnboy6083]

to be honest, the amount of sparks i see who dont know how to do this depairs me. Its sad that i didnt even think to see if it was a DIYer. I assumed it was a spark.

Most sparks i work with, only know how to read the standard circuits listed n appendix 8 of the OSG.

 

[topquark]

What is the rating of the fluorescent tubes? What are your earthing/bonding arrangements to be? (you may need 4 core swa as using the armour for your earth may not be sufficient if it works out that you need 16mm, depending on the type of swa sheathing).

You should just use an MCB at the main "fuse board" as you are intending to use RCD protection in the outbuilding.

 

[micknew]

Totally agree, B&Q must love this website!!!!
The site for advice for DIYers.

 

[clicon357]

Case in point, my best mate (a chippy) rang up one time, the conversation went roughly like this:

"I'm after a bit of armoured"
"What for?"
"The hot tub, the bloke said either 4mm or 6mm will do?"
"What bloke?"
"The hot tub bloke, he said if I run the cable their "electrician" will connect it"
"Well how longs the run, what load?"
"I ran a bit of string down the garden and its 33m"

He came down to my place with his bit of string. I measured it at 27m". I did a quick calc and gave him a length of 6mm and off he went. The hot tub people came in. Fitted a new 32A breaker to his existing board that stuck out too much, closed the clear plastic lid on it and broke one hinge. At the end of it all no certs given either! My mate and his missus paid by cheque as well. The hot tub install cost them £8K. Said he should take it up with them but he's too nice? Mind you he's also been caught twice by people phoning up and asking for his bank details.

It's a tricky one especially with friends and family do you try and help to a point or let them go and fit the length of 2.5 SWA they nicked from work?

My own brothers attitude to outside power - two extension leads run the length of the garden. The reel of one and the plug of the other jammed up a plum tree and covered with a couple of Sainsbury's bags. I HAD to say something I mean I might need a kidney one day!

IMO places like B&Q should only sell to someone upon presentation of qualifications / proof of competency at the till!

 

[Engineer54]

As i've said before and i'll say it again now ....We are NOT the ''Electrical Police'' and nor should we be!! I can understand about you may needing a kidney in the future, but how are you going to stop your brother or anyone else, running an extension reel up the garden and leaving it wedged up a tree?? lol!!!


When you start ledgistration like you propose, it tends to have far reaching affects on you and everyone else. Not to mention increases in materials that is going to put your own costs up. So leave the numbties of this world to get on with it, you'll never going to stop them anyway. It'll be you, or people like you after all, that will charging fee's to put the lash-ups right at the end of the day...lol!!!

 

[needasparks]

Don't worry, Wickes and B&Q both sell swa but don't sell glands for it. It still amazes me the different ways people connect them. The best iv'e seen was chock block in a jelly mould.

 

[i=p/u]

i learnt the sum in the big red book for this last week ,pretty easy when you shown how... id say mcb tooat main board but can go either way if you know what you at...

What is the rating of the fluorescent tubes? What are your earthing/bonding arrangements to be? (you may need 4 core swa as using the armour for your earth may not be sufficient if it works out that you need 16mm, depending on the type of swa sheathing).

You should just use an MCB at the main "fuse board" as you are intending to use RCD protection in the outbuilding.

 

[i=p/u]

i was putting up cctv in a house in south of ireland and seen the mans son connecting up swa in the garden , he just cut back the armour andput in connector blocks in box and put about 100mm below grass....

 

[clicon357]

As i've said before and i'll say it again now ....We are NOT the ''Electrical Police'' and nor should we be!! I can understand about you may needing a kidney in the future, but how are you going to stop your brother or anyone else, running an extension reel up the garden and leaving it wedged up a tree?? lol!!!


When you start ledgistration like you propose, it tends to have far reaching affects on you and everyone else. Not to mention increases in materials that is going to put your own costs up. So leave the numbties of this world to get on with it, you'll never going to stop them anyway. It'll be you, or people like you after all, that will charging fee's to put the lash-ups right at the end of the day...lol!!!

You're right, its me just sounding off! The friends and rellies I get asking for "advice" when invariably they've already done it! Constantly have the argument with my brother in law over twisting the cores together to go into the back of double sockets - losing battle! Another relative - his RCD doesn't work - I've offered to change the whole board FOC but that's too much trouble seemingly - FOR HIM! The best one I've come across is a friends ring circuit where he got some 5 core 2.5mm Y-Y cable "from work". Cores are labelled 1,2,3 & 4 - all black plus a CPC. Must try and get a photo its a corker!

 

[Big n Daft]

I have no truck with DIY "sparks"at all.To coin a phrase "they should all be taken outside and shot"

 

[clicon357]

I have no truck with DIY "sparks"at all.To coin a phrase "they should all be taken outside and shot"

Now you've done it, 20,000 complaints incoming, public apology etc etc!

 

[1shortcircuit]

With respect whilst it may seem that the OP may be a DIYer there was nothing to confirm.

I too have seen many posts where I have thought this may be the case.

Either way, whether it be a spark being lazy (which we also see all too often) a 5dw DIYer or a relative why can't we if asked provide an answer?

Yes it may be putting someone out of a job but if the person wants to do it themself then they either believe they are competent or they don't have the money to pay a spark? If it's the latter then advising them to get a spark in to quote may waste more than one persons time and efforts.

WITHIN REASON I do believe that there is no reason why the answer shouldn't be given, so long as the OP is informed that Local Authority Building Control will need to be informed before the work commences and when the work has been completed so that it can be tested and THEN energised and signed off. That advice alone may just save someones life.

I look at this post and see that someone has made the effort to find out what they need to do beforehand, who's to say that the OPwon't realise that they're out of their depth and quickly get a spark in?

Remember also, this is a PUBLIC forum so everyone with access to the internet can read what has been posted about things like replacing their own consumer unit and running power to Hot Tubs etc so I think it should be encouraged that members of the public come on here to request sound advice and if they kilk themselves in the process or burn their houses down the sobeit? They'll try even more if all they read is "Get a qualified spark in" oh but then that then raises the issue of make sure it's not a 5dw because they undercut REAL sparks. Oh but then having said that, your neighbour the real spark who has just been laid off of that huge construction site can't do it because he isn't part p registered blah blah blah.

If members don't want to help then they should click the back button and move onto the next thread.

Sorry to have taken this off topic but it annoys me to see people with the ability to assist moan about people posting on an ELECTRICIANS public forum about work that they are considering having done.

There sre some very blinkered SPARKS on here!

That's all folks lol have a great weekend

---

1SC

 

[clicon357]

I do err on the side of trying to help when asked and I know some folk are dead against it quoting putting sparks out of work etc etc. In the back of my mind I always hope they take away just a little bit of what I've said so even if they attempt it, it lessens the chance of them or theirs getting a belt. Just making the point that a lot of people do it first THEN ASK as if by some miracle their asking an electrician after the event will make everything ok. The calls I get on the lines of "I've done so and so, that'll be alright won't it?". So yes, credit to the OP for the asking. I must admit though on this forum that because of some of the "against" comments to DIY'ers posts being so "strong" it means that I PM the DIY'er and try and help that way. Maybe a collective move to answering the DIY'ers a little more gently even if only to say get someone qualified in? A lot of the posters must Google the forum, see it says the "place for electrical advice" and post a fair question. Seeing some of the answers and they must really think "What a bunch of I MUST NOT SWEAR"!

 

[1shortcircuit]

they must really think "What a bunch I MUST NOT SWEAR"!

Exactly, then they take that away and tar every spark with same brush. Add to this how much a spark wants to charge and it becomes "what a bunch of rip off I MUST NOT SWEAR"

Provides a real reason to use a qualified, professional spark wouldn't you agree lol