OUTSIDE SHED

[mngray]

I would like to run electricity to my shed in the garden, and will obviously have to get a qualified elecytrician to do the difficult bit. However I want to lay the cable myself and run it to the MCB in the house for the electrician to fit. I have a couple of questions, but first the details:

50m from house to shed.
Planning a lighting circuit (3 x 60/100W pendant lights plus an outside halogen on a sensor)
A plug circuit (4 x double sockets inside and a waterproof outside socket) to run drills, strimmers, power saws and lawnmowers.

The questions:

What sort of MCB do I need in the shed?
What type of armoured cable should I lay (in mm and numbers of cores)?
Anything else I need to Know?

Thanks

 

[big-all]

heeelllooo mngray

this is the consumer unit i have in my workshop
http://www.toolstation.com/search.html?searchstr=garage+consumer+unit&Search=1

http://www.toolstation.com/messages.html?closeUp=46766

 

[plugwash]

first you have to decide on a current rating for the cuircuit to the shed. 20A is about the absoloute minimum you should consider designing for but many would advise more like 40A to allow for any future uses of the outbuilding (you only wan't to dig that trench once)

for a 40A cuircuit due to the volt drop issues over such a long run at least 10mm cable is in order 16mm is preferable to allow for some volt drop in final cuircuits etc.

 

[mapj1]

If it is essentially a toolshed rather than a workshop, then a 16A radial for the sockets plus 6A mcb for what is really less than an amps worth of lights will probably be OK.
If its more or less garage sized, or you might one day have something big in there, then a 30A power circuit with a proper ring or 4mm radial layout is in order (or 2 independant 16A radials has advantages). As has been indicated, over that distance, acceptable voltage drop will define the cable size, rather than the current rating in the conventional sense, and you will need 4mm or 6mm cable for the lighter options, and as suggested 10 or 16mm for the 'full monty'
Is your incoming supply TT, TNC or TNS? this affects if you need a local earth rod, or if you would be using the earth as supplied from the supply end. In any case I'd strongly recommend an RCD at one end or the other, as it sounds like outdoor tools will be used.
If taking the earth from the supply, it is as well to use 3 core cable, rather than rely on the armour, although for certain sizes the armour may, or may not, be low enough resistance to be acceptable as the only earth.
The other consideration is where the supply is coming from - is there a free 32a breaker or 30A fuse in the consumer unit or is another one of those needed too? And is theincoming supply up to the possibel combined load.

The best bet, if you are not DIY ing is to ask the sparks what he would consider appropriate.

Otherwise size it for the most you might reasonably do, rather than the least.

good luck

 

[ban-all-sheds]

Do a search here for shed, garage, outhouse, outside, etc - you'll find all the info you need.

Also, are you aware of Part P? I know you're getting an electrician, but if he's self-certifying he'll want to see how deep the trench is, check the material the cable is bedded on, check that warning tape is used etc. If he's not self-certifying you need to decide what you're going to do regarding the legal obligation to submit a building notice.