wiring to garden sheds.

[johnston1991]

hello im new to this i am a level 2 qualified electrical apprentice,

we have decided to wire up the two sheds in the garden and i have drawn up a basic plan of the wiring, could you take a look and let me know if it looks safe? the plastic conduit will be clipped to the bottom of wooden fence pannels,

many thanks

 

[Badger]

firstly, use 6mm 3 core armoured instead of 4mm and pvc conduit. to top shed as the main supply, and use 4mm 3 core armoured to the bottom shed between those shed and rate that at 20 amps. other than that cant see a major probem there,

 

[johnston1991]

okai thanks for the advice will replan it around that

thanks

 

[Badger]

oh and the bottom shed sockets should be rated at 16a not 32 maybe 20 if you really think as 2.5 can take 27amps clipped direct.

 

[Andy™]

for the bottom 'ring', maybe a 4mm radial instead?

 

[Badger]

yeah that might be better and easier.

 

[Evans Electric]

A ring main in the bottom shed ?? Sounds over the top, how big is shed, how many sockets ? Other wise I'd go with the Badger.

Deke

 

[Evans Electric]

Posh drawing though !! Applaud Smiley

Deke

 

[Badger]

just a point evan elec i put a ring main in our shed and niceic looked at that as one of my first installs i did.

 

[johnston1991]

thanks for all the information and the ring in the shed was only having 3 or 4 double plug sockets, so 4mm radial a better idea?

 

[KR Sol]

Firstly Hi Johnston1991 and good choice of career I hope the apprenticeship is going ok? The circuits don't appear to be RCD protected? Also you are exporting the cpc from the house I can see Mr Steptoe having a few thoughts on that lol.

 

[batty]

Hello Johnston welcome to the forum.

The two things I have picked are it is not good practice to fix cable to wooden fences at some point they may need replacing and also if they are blown over cable could be damaged.

The second point is it is not good practice to export the earth from the house especially if it is pme.

Batty

 

[johnston1991]

hi the circuit is pretected by an 63A rccb up at the main consumer unit? would that not cover it? and thanks its going well and yes i was planning on running the cpc straight off of the supply in the main c.u no good? now iv been advised to use SWA il be running it underground..

thanks

 

[Andy™]

hi the circuit is pretected by an 63A rccb up at the main consumer unit? would that not cover it? and thanks its going well and yes i was planning on running the cpc straight off of the supply in the main c.u no good? now iv been advised to use SWA il be running it underground.. thanks

itll need a 30mA RCD - you havent said what rating the 63A is, but there is a good chance its 30mA. But you might want to install a seperate RCD for outside. a fault outside could put the entire house into darkness

its normally a bad idea to export TNC-S. you can export TT and TNS

SWA is the best choice for what you want. dont forget to bury it 450mm deep and it needs marker tape

 

[johnston1991]

ye sorry the rcd is 30mA there isnt any room in the main c.u for another one would it be ok to put it into the second one in the first shed?

for my cpc i would use a TT setup with an earth rod ect then ye? ?:|

thanks

 

[Andy™]

ye sorry the rcd is 30mA there isnt any room in the main c.u for another one would it be ok to put it into the second one in the first shed?for my cpc i would use a TT setup with an earth rod ect then ye? ?:|

thanks

If the house is TT, then the RCD must go in the house. otherwise optional, but strongly recommend the house. you could always split the tails and install a 2nd mini cu. or a breaker not on the RCD then through a seperate RCD.... or i DP switch before the SWA to if there is a fault outside, you can easily disconnect both live and neutral

Whats the current earthing in the house?

 

[SLIPSHOD & SLAPDASH]

May i add the following points for your perusal. As you area adding a new circuit the 17th edition prohibits the use of just one Rcd on an installation. Putting that aside, from a practical point i would not group this new circuit onto the house rcd. Split the tails before the existing rcd and fit a new mini board with a Rcd main switch and your choice of breaker.

I recently fitted some Hagar 25a Mcb's to get round the discrimination over the32A in the Main board. They only cost

 

[johnston1991]

ok im sure i can make space for a small c.u and just run the rcd tail to the primary ye?

and im pretty sure the earthing system is TN-C so i shouldnt export that right?

 

[Andy™]

ok im sure i can make space for a small c.u and just run the rcd tail to the primary ye? and im pretty sure the earthing system is TN-C so i shouldnt export that right?

correct.

you should add RCD to house, use PME earth to earth SWA. at shed, terminate into a plastic enclosure, do not connect to the earth of the armour. install rod and use that as your earth

or you could install rod at house, then to SWA armour, ditching the PME earth

 

[johnston1991]

ok thanks il draw up a plan for tomorow and get it on here if you wouldnt mind checkin it all looks good ,

many thanks