Requirements to power a shed

quattroman · 22 Aug 2011

Hi all. I am planning on running power to a shed and then power 2 x spurs, with one twin socket on each, and 3 separate lighting circuits (2 x 60W and 1 x 500W floodlight).

Unfortunately the shed is 60 metres from the Consumer Unit in the house that I need to take the power from. Was planning to used Armoured Cable and bury it.

Can anyone let me know :
1.what I need to use at the House Consumer Unit (RCB / MCB);
2. the size of cable from house to Shed;
3. the size of RCB/MCB's in the shed to run the circuits described.

Thanks,

Quattroman.

ban-all-sheds · 23 Aug 2011

But realistically? You can't do it yourself, not any time soon.

The thing is, installing new CUs, outside supplies, submains etc is not a trivial job, and I can assure you that it involves knowing far more than you think it does.

Asking questions here can be a useful part of a learning process, but they are not a substitute for proper structured studying. The key term there is "learning process" - you cannot learn all the things you need to know just by asking questions here. It isn't structured enough - it won't provide you with a way to progress where each step builds on what you learned before.

You can't carry out a job of this magnitude by asking whatever random questions happen to occur to you. It's clear from the questions you've asked that you really do not have anywhere near enough experience to be tackling a job like this - what if you get something wrong because you have no idea your knowledge is wrong? What if you miss something because you simply have no idea it even exists, and just don't realise you don't know it?

//www.diynot.com/wiki/electrics
//www.diynot.com/wiki/electrics:books
http://web.archive.org/web/20080213151445/http://www.kevinboone.com/electricity.html
http://web.archive.org/web/20080213151445/http://www.kevinboone.com/domesticinstallations.html
http://www.tlc-direct.co.uk/Book/1.1.htm[/list]I suggest you get stuck into the last link right away - it won't give you design ideas, and unfortunately it doesn't refer to the current edition of the Wiring Regulations, but it's free, and will still give you a good grounding which you can augment with more up to date publications.

ericmark · 23 Aug 2011

The answer by BAS is spot on. However I also realise people will go ahead anyway so real basic wiring to a shed first you want a metal box to be able to terminate SWA into without warping. Using a socket box is easy option. Also limiting total supply to 13A makes life easy. So if you use a RCD FCU like this

or this

at the supply end it makes life easy use cheap type active normally but use expensive passive type if a fridge or freezer are to be used. Because of distance I would consider 4mm sq although I have not worked out volt drop just a guess. And at the shed I would use Switched FCU's as light switches and fuse down to 3A.
This is a very basic way to wire a shed and if you want to use heaters and other heavy equipment then it's no good.

However it will likely pass when you submit your plans to the LABC before starting work. If you think you may wish to up-grade latter then use thicker cable.

To be honest by time you hire the test gear needed to submit your results to the LABC and pay the LABC fees it is likely cheaper to just dig trench then get a local scheme registered electrician to do the job for you.

But once you go over the 13A limit the price will rocket up. So consider what you want to use in the shed.

ericmark · 23 Aug 2011

A PS using over 150W light outside also needs permission from council so you may also want to consider size of light used.

mikerodent · 23 Aug 2011

Hi,
Home owners are allowed to do small work on thier own electrics.
Final sub circuits are okay.

Your load is 500w for lights.
Sockets the biggest item you will plug in. You will only use one at a time unless you are an octopuss.
say 1000w for a bench tool

That gives you 1500w. About 6amps.

You can use 2.5mm 3 core pvc swa. Or 4mm if the price is not a lot
higher. These will give you less than 10vd. If I have my decimal point in the right place.

You need a 10Amp RCD. And bury the cable at a depth where it will not get hit with a pick at some future date.

The floodlight will only be a council issue if a next door complains about it. or you dazzel traffic. Look in the council guidlines.

Mike

MalcofArabia · 23 Aug 2011

Hi all. I am planning on running power to a shed and then power 2 x spurs, with one twin socket on each, and 3 separate lighting circuits (2 x 60W and 1 x 500W floodlight).

Unfortunately the shed is 60 metres from the Consumer Unit in the house that I need to take the power from. Was planning to used Armoured Cable and bury it.

Can I ask why you want to fit 2 spurs and run a double socket of each spur, or do you mean fit 2 double sockets and then spur for the light.

Do you know what earthing system you have as if it is TT then the chances are you will need to fit RCD protection to the SWA.

I'm assuming that the shed is not a metallic type, or there are any services out to it ?
[/i]

ban-all-sheds · 23 Aug 2011

mikerodent said:
Hi,
Home owners are allowed to do small work on thier own electrics.

They are allowed to do any sort of work, as long as they are competent.

Some work is notifiable and requires approval to be sought in advance.

Final sub circuits are okay.

They are notifiable - of that there is zero doubt.

You can use 2.5mm 3 core pvc swa. Or 4mm if the price is not a lot
higher. These will give you less than 10vd. If I have my decimal point in the right place.

Just being less than 10v is not sufficient, and 2.5mm² won't do.

You need a 10Amp RCD.

MCB, surely?

The floodlight will only be a council issue if a next door complains about it. or you dazzel traffic.

quattroman · 26 Aug 2011

Thanks mikerodent. Not sure about the other responses yet... esp BAS.

It is legally acceptable to do the electrics yourself under the supervision of a qualified electrician who can then check the installation and sign it off.

My main concern is to get the correct size of cable for teh length involved and then what circuit breakers willbe required to account for the voltage drops, etc.

In the shed, I was hoping to run 2 spurs with a double socket on each of them, and 2 lighting spurs along with 1 x 500W exterior security light.

Have already had a friend run the details through electrical an computer program which reckoned on 10mm cable which seems a bit extreme.

So that is why I am looking for other recommendations.

Thanks,

Q.

Alarm · 26 Aug 2011

Not according to this.

[/URL]

[/img]

riveralt · 26 Aug 2011

quattroman said:
It is legally acceptable to do the electrics yourself under the supervision of a qualified electrician who can then check the installation and sign it off.

It is though the extent of your supervision needs to be discussed in detail with the electrician. As for mikerodent, ignore him, he doesn't seem to know what he is talking about.

quattroman said:
My main concern is to get the correct size of cable for teh length involved and then what circuit breakers willbe required to account for the voltage drops, etc.

Something to be agreed with the person who will supervise, test and sign off the work to the Local Authority Building Control.

quattroman said:
Have already had a friend run the details through electrical an computer program which reckoned on 10mm cable which seems a bit extreme. So that is why I am looking for other recommendations.

Trying to bypass the rules and regulations is the surest way to end talking to the devil

Paul_C · 26 Aug 2011

mikerodent said:
Hi,
Home owners are allowed to do small work on thier own electrics.

That needs clarifying. A homeowner is allowed to do any electrical work he wishes. The statutory limitation is to whether the particular work is supposed to be notified to the local authority or not, and the question of whether or not it's "small" work is rather irrelevant: It depends upon what the work involves and in some cases where it's located. For example, you could quite legally add a dozen sockets to existing circuits in the living room and bedrooms without notification being required. But add one external socket by taking all of a foot of cable through a wall from an inside socket, and it's notifiable, at a cost of anything from £100 to over £400 depending upon the area.

The list of non-notifiable works can be seen here:
http://www.legislation.gov.uk/uksi/2010/2214/schedule/4/made

Final sub circuits are okay.

Again, it depends what you're doing to a final circuit, as per Schedule 4.

say 1000w for a bench tool

That gives you 1500w. About 6amps.

Allowing for a mere 6 amps maximum load to multiple 13A sockets is not a good idea in my opinion, regardless of whether you might think it adequate at the outset. And even if a 1000W grinder, drill, circular saw etc. is likely to be the highest rated appliance used, don't forget that the switch-on surge for such motors will be considerably more than that. Over 60m. of 2.5 sq. mm. feeder, the momentary voltage drop at switch on is likely to be unacceptably high.

quattroman · 26 Aug 2011

Hey Alarm.. thanks for that.

Guess it will have to be the 10mm cable then... once I get round to it.

flyingsparks · 26 Aug 2011

mikerodent said:
Hi,
Home owners are allowed to do small work on thier own electrics.
Final sub circuits are okay.

Your load is 500w for lights.
Sockets the biggest item you will plug in. You will only use one at a time unless you are an octopuss.
say 1000w for a bench tool

That gives you 1500w. About 6amps.

You can use 2.5mm 3 core pvc swa. Or 4mm if the price is not a lot
higher. These will give you less than 10vd. If I have my decimal point in the right place.

You need a 10Amp RCD. And bury the cable at a depth where it will not get hit with a pick at some future date.

The floodlight will only be a council issue if a next door complains about it. or you dazzel traffic. Look in the council guidlines.

Mike

Considering you clearly have no idea what your talking about, you really shouldn't be trying to advise people what to do regarding electrical work. Moron.

ban-all-sheds · 26 Aug 2011

Alarm said:
Not according to this.

[/URL]

[/img]

Curious.

According to 4E4B, 10mm² XLPE SWA has a VD of 4.7mV/A/m.

So how does 26.09A over 60m drop 6.3V?

According to my trusty Casio, 0.0047 x 26.09 x 60 = 7.4...

Alarm · 26 Aug 2011

ban-all-sheds said:
Curious.

According to 4E4B, 10mm² XLPE SWA has a VD of 4.7mV/A/m.

So how does 26.09A over 60m drop 6.3V?

According to my trusty Casio, 0.0047 x 26.09 x 60 = 7.4...

Look very carefully at this at the top

Calculator for General Guidance Only

Seems close enough to confirm the 10mm though, or do have a better online calc?

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Requirements to power a shed

Alarm

Paul_C

Alarm

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