New garden shed supply and garden sockets RCD protection?

[AussieP]

Hi, I need some advice on a garden supply project. An existing small garden shed is being replaced which had a supply to it for a light and two sockets , and a radial socket circuit which continued around the garden. The old installation had a 6mm supply coming into a 63A 30mA RCD as a main switch.
I am wondering how best to supply the new shed and outside radial sockets. The power demand will be a small fridge , kettle use occasionally , electric lawn mower of the sockets etc. The radial socket circuit is quite long ( 40meters or so ) Origin of supply is a split board both sides RCD protected.
Should i run a 6mm or 10mm SWA from DB in the house ( RCD protected ) to a 3way DB in the shed ? The volt drop will be too great for the outside sockets on a 2.5mm T&E due to the run being so long. The shed DB will need a RCD as a main switch right? due to lighting and sockets being on the supply?

Cheers

 

[Mikegh]

The best way is no Rcd on the swa itself


Incommer at the shed and Rcbos in the sub board

 

[Spoon]

Welcome to the forum mate.

Let me get this straight:
You have an existing supply going to your shed. 6mm SWA cable. Wired to a RCD in the shed?
You then have a radial circuit from the shed, 40 meters long, going to sockets in the garden and a circuit inside the shed for a couple of sockets?

Questions.
What is the distance from the house CU to the shed RCD?
What is the 6mm wired to at the house CU?

Seeing that the house CU has RCD protection then the shed CU doesn't need to have it, as it's protected by the RCD in the house CU. Otherwise you then have to have selectivity between the house RCD and the shed RCD/RCBO's.

 

[AussieP]

Welcome to the forum mate.

Let me get this straight:
You have an existing supply going to your shed. 6mm SWA cable. Wired to a RCD in the shed?
You then have a radial circuit from the shed, 40 meters long, going to sockets in the garden and a circuit inside the shed for a couple of sockets?

Questions.
What is the distance from the house CU to the shed RCD?
What is the 6mm wired to at the house CU?

Seeing that the house CU has RCD protection then the shed CU doesn't need to have it, as it's protected by the RCD in the house CU. Otherwise you then have to have selectivity between the house RCD and the shed RCD/RCBO's.

Hi ,
My sister just moved into the property, the supply to the shed was taken from an upstairs socket !!! (so spurred off the upstairs ring, gut feel is that is naughty) through the wall and run on a wire to the shed !!! (PVC twin&earth). I have disconnected that and stripped out everything in the shed (as it is getting knocked down and rebuilt).
I paced out the run for the SWA to the CU in the house and is roughly 20 odd meters when you track round where it can be buried out of site.
There needs to be some sort of switch control in the shed for the circuits there right ?

 

[DPG]

Hi ,
My sister just moved into the property, the supply to the shed was taken from an upstairs socket !!! (so spurred off the upstairs ring, gut feel is that is naughty) through the wall and run on a wire to the shed !!! (PVC twin&earth). I have disconnected that and stripped out everything in the shed (as it is getting knocked down and rebuilt).
I paced out the run for the SWA to the CU in the house and is roughly 20 odd meters when you track round where it can be buried out of site.
There needs to be some sort of switch control in the shed for the circuits there right ?

You're saying the 6mm feed to the shed was taken from an upstairs socket?

 

[AussieP]

You're saying the 6mm feed to the shed was taken from an upstairs socket?

Yep ! I isolated supply to that ring and disconnected it and stripped everything out of the shed.

 

[pc1966]

If you really don't need much power then feeding out 20A RCD protected supply for a radial with a few sockets, and using a 3A FCU for light switch would be simple.

 

[AussieP]

Fused-switch, was a brand's part number name at one point (like hoover, etrc)

Sorry for the silly question now ! I am confused by splitting the tails now . I only have 2 spare spots on the CU which is RCD protected. I want to take a feed from the CU to the shed which will have 3 circuits . can I still have a 3/4way DB in shed as long as no RCD? is it a case of a fused switch controlling those circuits?

 

[Mikegh]

There's 3 ways

The way I told you gives the best discrimination

The least desirable method is connecting to the house rcd

 

[AussieP]

The best way is no Rcd on the swa itself


Incommer at the shed and Rcbos in the sub board

Hi Mikegh , when you say " Incommer " at the shed , do you mean it connects to a sub board with just a main switch, and 3 x RCBO's for the circuits ? I will run with that if that's what you mean.

I appreciate everyone responses , thanks for taking the time to reply. I probably sound like an annoying idiot now!

 

[DPG]

Have you got a calibrated MFT?

 

[AussieP]

Have you got a calibrated MFT?

yes , Fluke 1664

 

[westward10]

Your posts suggest this is way beyond your area of competence and whilst the forum is happy to help DIY members within reason it draws a line under giving step by step advice. You may well be helping your sister but the most appropriate advice is for her to use an electrician who can certify the installation and where necessary notify it to Building Control.