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New shed - advice on electrics please

Postby PJH2903 » Tue Jun 03, 2008 4:33 pm

I am installing a new shed in my garden and would appreciate some advice about the electrics please.

I intend to get an electrician to connect and test the system for me once it has been completed but would like some advice on the following:

1) I understand that swa is normally burried but would it be acceptable to secure it above ground on the concrete fence bases?

2) I intend to have a light and 6 sockets in the shed to run a freezer and occasional power tools.
A) what size cable should I use
B) can I spur off the conservatory - 15 m or do I need to run from the consumer unit - 26 m

Thanks in advance
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Simply Build It

Postby ericmark » Tue Jun 03, 2008 5:30 pm

1)Yes you can normally attach the SWA to a fence etc.
A) Cable size will depend on total length, earth loop impedance etc. etc but in most cases we look at between 6 and 10 mm.
B) Maybe.
So lets look at information required.
1) Type of earth system feeding house.
2) What is the PSC at the house.
3) What is the Ze at the house.
4) Are there any exterior metal parts to the shed that will need bonding.
5) What is the max demand likely from shed i.e. 3Kw electric fire, Lights, Screw cutting lathe, etc.
Once these questions are answered it will likely generate more. It can be very simple it can also be complex and with consideration it will come under Part P and every thing done will be checked it needs to be correct.
Any new circuit can be split into three parts.
Inspection and testing
If a Part P registered electrician does all three parts he can self certify the whole installation. On the other hand if some parts are not done by him the council building control needs to get involved and their fees paying. So to do part your self can cost more than getting a registered electrician to do whole job. If the shed is metal or if it has any services into it like water the earthing arrangements can become complex especially if the house uses a TN-C-S system (PME) the IET web site has a two or three page info sheet on how to wire sheds we are not allowed to give links.
It might be very easy but if we tell you it is easy then you find out with what you intend it is more complex you would not thank us better to find out exactly what you intend.
All best Eric

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