Electric supply to shed

[cono]

Hi
I wish to take a supply to my shed. My interest is woodwork and sometime in the future I will be purchasing a bandsaw, the one I have in mind requires a 20amp supply. Plus the usual DIY tools such as a chop saw, router etc which will run from a 13amp supply.
The consumer unit which supplies electric to the house is in the garage. It is an old fashioned one, i.e. it uses rewireable fuse carriers, there are 6 in total, there are no spare fuseways. I guess it would be adviseable to change this with a modern one which also includes an RCD. Is it a good idea to use what I believe is called a split box?
The distance from existing consumer unit to shed is 24 mtrs.
I intend to use armoured cable buried 450mm deep with paving slabs over the top. In the shed I will have 4 flourescent lights and 6 double metal socket outlets, at any one time only the lights and one socket outlet will be in use. I intend a radial circuit for the socket outlets with a junction box feeding the lights.
What rating would be adviseable for the armoured cable?
I realise that I will have to comply with the latest regulations and will have the work checked by a qualified electrician who will I understand notify the appropriate body of the work carried out.
Any advice and recommendation will be greatfully received, many thanks for help. Apologies for a rather lengthy post, no doubt I will have missed something.

[Steve]

Given that you are having a dedicated 20A supply for one piece of equipment at the shed, i would recommend a submain of no less than 40A. This will require 10m² SWA and yes, you will need to change that outdated old wylex board in the garage.

please ask an electrician first, becaus it is actually illegal for them to sign off someone else's work. if your house burns down, they will get the blame because they put their name to your work. Also ask your local council building control for advice regarding complying with part p of the building regulations.

[WabbitPoo]

crafty1289 wrote:

This will require 10m² SWA .

M? isnt that a BIG cable? Forgive my ignorance of terminology if not, but should that be mm?

[cono]

crafty1289 wrote:

Given that you are having a dedicated 20A supply for one piece of equipment at the shed, i would recommend a submain of no less than 40A. This will require 10m² SWA and yes, you will need to change that outdated old wylex board in the garage. please ask an electrician first, becaus it is actually illegal for them to sign off someone else's work. if your house burns down, they will get the blame because they put their name to your work. Also ask your local council building control for advice regarding complying with part p of the building regulations.

Crafty 1289
Many thanks for your helpful advice. Regarding the illegal aspect would it be OK if everything was made ready for the electrician, i.e. trench dug, socket outlets (backs) put where I require and the fluorescent lights placed in position but not connected? Also is it a good idea to have a split consumer unit when replacing my old one?
cono

[RF Lighting]

cono wrote:

Regarding the illegal aspect would it be OK if everything was made ready for the electrician, i.e. trench dug, socket outlets (backs) put where I require and the fluorescent lights placed in position but not connected?

Yep. No problem with that.
If you put a duct into the trench, then you could back fill the trench too.

I would recommend installing a duct, as this will allow you to replace the cable without the need to dig up the garden again, should you ever want a bigger supply, or in the unlikely event that the cable gets damaged.
If you do fit a duct don't forget to put a draw rope through to enable the cable to be drawn in.

Also it may be worth running a second duct to the shed, as now is the time while you have the trench up, even if you don't use it now, it will be there for the future. This will allow you to run things like a burglar alarm cable (not a bad idea with all those power tools), telephone, TV, internet etc.

Quote:

Also is it a good idea to have a split consumer unit when replacing my old one?

You will need to provide RCD protection to any socket outlets likely to supply equipment for use outdoors, and the most common way of doing this it to fit a split load board, but another way of acheiving this is to fit a standard consumer unit fitted with RCBOs to protect the sockets. This is a bit more of an expensive way to do things, but if a fault occours on one of the protected circuits, it will only trip the affected circuit, rather than a split load board which would cut the power to all the protected circuits.

[cono]

RF Lighting wrote:

cono wrote: Regarding the illegal aspect would it be OK if everything was made ready for the electrician, i.e. trench dug, socket outlets (backs) put where I require and the fluorescent lights placed in position but not connected? Yep. No problem with that. If you put a duct into the trench, then you could back fill the trench too. I would recommend installing a duct, as this will allow you to replace the cable without the need to dig up the garden again, should you ever want a bigger supply, or in the unlikely event that the cable gets damaged. If you do fit a duct don't forget to put a draw rope through to enable the cable to be drawn in. Also it may be worth running a second duct to the shed, as now is the time while you have the trench up, even if you don't use it now, it will be there for the future. This will allow you to run things like a burglar alarm cable (not a bad idea with all those power tools), telephone, TV, internet etc. Quote: Also is it a good idea to have a split consumer unit when replacing my old one? You will need to provide RCD protection to any socket outlets likely to supply equipment for use outdoors, and the most common way of doing this it to fit a split load board, but another way of acheiving this is to fit a standard consumer unit fitted with RCBOs to protect the sockets. This is a bit more of an expensive way to do things, but if a fault occours on one of the protected circuits, it will only trip the affected circuit, rather than a split load board which would cut the power to all the protected circuits.

RF Lighting
Thank you for your helpful advice. I shall certainly put ducts in, I intend to use either 40 or 50mm plastic pipe, the lengths connected with straight connectors. Will this be OK?
This is the first time that I have used a forum--hope I am responding to the posts giving me such helpful advice correctly.
cono

[RF Lighting]

40mm might be a bit on the small side, but 50mm should be fine. Try to keep joints to a minimum and avoid any tight bends as the cable may catch on these when being pulled in, which may result in having to redig part of the trench

Dont forget to put a strong rope in each duct.
Also you should put warning tape in the trench. 1 length just above the cables, and 1 length near the surface.




Buy it here

[JohnD]

RF Lighting wrote:

... another way of acheiving this is to fit a standard consumer unit fitted with RCBOs to protect the sockets. This is a bit more of an expensive way to do things, but if a fault occours on one of the protected circuits, it will only trip the affected circuit, rather than a split load board which would cut the power to all the protected circuits.

Well done that man!

[toasty]

10mm² ? Are you sure?

You can use 6mm² for a 40amp load up to 30 odd metres for pvc or xlpe and save your self a few quid not to mention the hassle of working with a thicker cable.

Crafty, I think you are confusing T&E with SWA.

[securespark]

I back Crafty. That way, you have future-proofed the installation.

__________________
As George Michael once said, "..if you're gonna do it, do it right, right?"

[toasty]

Agreed, future proofing is a good idea, but the point I'm making is that 40amp over 24meters doesn't require 10mm.

6mm is more than adequate.

[securespark]

Toasty - I don't have my regs with me - remind me what the VD values are for SWA multicore 6 & 10mm2...

__________________
As George Michael once said, "..if you're gonna do it, do it right, right?"

[cono]

securespark wrote:

I back Crafty. That way, you have future-proofed the installation.

A big thanks to everyone on this forum for their comments. They are very, very helpful and have put me right to have everything done safely and future proof the installation-which is great! I shall start digging the trench soon, unfortunately I have to move a couple of trees and will have to wait until there dormant, but in the meantime can dig either side
cono

[toasty]

securespark wrote:

Toasty - I don't have my regs with me - remind me what the VD values are for SWA multicore 6 & 10mm2...

Me neither, just use the TLC calculators, they are pretty good.

http://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html