Supply electricity to a shed.

[Lectrician]

No mention of an RCD anywhere in your plan.

And yes, why 3amp fuse for each socket?? I can see them blowing!!

I would put a 32amp min MCB at the start, and a 20amp in the shed for the sockets and a 6amp for the lights.

 

[Laine]

OK my bad i forgot about the ring formation i would use that anyway, i thought one of you guys told me to fuse all the socket individually?

RCD is on the consumer unit in the home (63A), BTW is it uncommon to have a electric meter which can take a max of 40A?

 

[Lectrician]

BTW is it uncommon to have a electric meter which can take a max of 40A? - Err...yes....is it the supply companies one?

OK my bad i forgot about the ring formation i would use that anyway. What do you mean RING info??

 

[ban-all-sheds]

Ok i have done my homework, had a look round the web and re done my plan.

I had a look in my home consumer unit all looks dandy, easy to fit a 20amp MCB.

At first you said "The only bit i am not that competent on is fitting the MCB on the switchboard" - are you now sure you're OK to do this?
Also, Lectrician has repeated his advice to use 32A - why do you keep saying you're going to use 20A?

From there i will run a 6mm SWA 3 core cable underground around 40 metres to the shed. This will then be terminated by a smaller consumer unit for ease.

I still don't think you'll be able to terminate the SWA in the CU.
And digging a 40m trench nearly 1m deep is not a quick job - to avoid any possibility of ever having to do it again I would strongly advise laying in 10mm cable - the extra cost of the cable is negligible.

Have you now determined what you need to do re. earthing?

 

[ban-all-sheds]

i thought one of you guys told me to fuse all the socket individually?

No - that was your idea. Although to be fair, nobody picked up on it first time round.

RCD is on the consumer unit in the home (63A)

Having the whole house on an RCD is a bad idea anyway, particularly when one of the circuits supplies a CO detector. Having the whole house on an RCD and supplying circuits in a shed 40m away is an even worse idea.

You should replace (or have replaced) the CU with a split-load board, and come off the non-RCD side for the shed, and have local RCD protection out there.

 

[Laine]

Can i not just put another RCD in the shed consumer unit?

and is it alright to use the earth that the home CU is attached to aswell for the shed? Or wil i need another earth pole for the shed?

got pix of my 40A meter here

www.laine.ndo.co.uk/site/meter1.JPG
www.laine.ndo.co.uk/site/meter2.JPG

 

[ban-all-sheds]

Can i not just put another RCD in the shed consumer unit?

You can, and indeed you must if you do change the house end and have a split load board with a the shed on the non-RCD side. But if you don't change the main CU (which as I said you should do anyway, shed or no shed), putting an RCD in the shed may not help - there is no guarantee of discrimination, i.e. a fault could just as easily trip the one in the house as the one in the shed.

and is it alright to use the earth that the home CU is attached to aswell for the shed? Or wil i need another earth pole for the shed?

Does "another earth pole" mean that you already have one, and that is how your house is currently earthed? Do you know if you have a TT, TN-S or TN-C-S (PME) supply? (see here for descriptions).

got pix of my 40A meter here

40A is too low - I'd ask the DNO to replace them.

 

[Laine]

Well the house has been newly earthed. We just moved in last month and the spark had to do it.

Before that the previous tennants that had lived there for 26 years had no earthing installed

 

[Laine]

everything is earthed via the CU.

www.laine.ndo.co.uk/site/earth.JPG
www.laine.ndo.co.uk/site/top.JPG
www.laine.ndo.co.uk/site/cu.JPG

 

[plugwash]

while that CU could be converted to a split you don't really have enough room in it (to convert to split and add you existing cuircuit you would have to remeve 2 current cuircuits which is probablly impractical)

probablly best to replace the CU but this usually entails pulling the service fuse and there is someone here that will jump down my throat if i suggest that to a diyer

 

[Laine]

Who is DNO? Is it just a case of ringing them up and saying that the appliances i use frequently exceed 40A (even tho they dont and probably wont)

 

[ban-all-sheds]

Who is DNO? Is it just a case of ringing them up and saying that the appliances i use frequently exceed 40A (even tho they dont and probably wont)

DNO is the network operator - not the people from whom you buy your electricity. Looks like it is (or used to be - who knows what they call themselves now) Eastern Electricity.

That looks like an earth rod to me, which means you have a TT supply.

So firstly, your CU is not ideal - it should be a split-load unit with a 100mA RCD protecting the entire installation (ideally time-delayed) and a 30mA one for the socket circuits.

Secondly, I would advise not coming off the house CU for the shed.

After the meter, install a henley block to split the tails - 1 set to the CU, another set to a metal box with a switch and an MCB. From there 6mm or 10mm SWA to the shed, terminated in a metal box. Shed CU with RCD protection, and local earth rod.

 

[plugwash]

erm if the only earth is a rod then there needs to be a rcd at the source of the shed cuircuit

 

[ban-all-sheds]

Why?

House supply - after the meter the tails run to the CU, which has an RCD, and a connection via the MET to an earth rod. There is no RCD at the beginning of the tails.

I'm proposing that after the meter, the tails&SWA run to a CU in the shed, which has an RCD and a connection to an earth rod. Just as with the house supply there will be no RCD at the beginning of the tails.

 

[plugwash]

i mean if the only earth availible in the house is a rod

if you are setting up a shed with its own earth system and the rcd is at the shed end then the cable armour should be connected to the house earth (and should not be exposed at the shed end)

a rod earth will not short cuircuit disconnect a cuircuit without rcd protection (with a few exceptions for a very good rod or a very low current cuircuir)