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Discuss Garden Shed Wiring in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

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daver

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Hi Guys and Ladies

Sorry for asking at a late hour, but I am DJing in a club at moment. Luckily we have WiFi, but I dont have any reference books with me. Doorman has just asked for a price to wire his shed. This is my first outside job, so be gentle.

All he wants is 1 socket for lawnmower and a light. Shed is 30M from the house. House is fully RCD'd. TNCS. The only option is to come of ring and fuse spur.

What size SWA.
What size Fuse.
Will it need spiking

Just want to try and cost tonight while we are quiet

Cheers

Dave
 
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iceman

  • Thread Starter Thread Starter
  • #2
hi u'll need a 20A circuit breaker if ya supplyin power to shed cable wise id use 6mm swa i hav used 4mm before now but 6mm is better if ya runnin it under the ground unless you want to run ya cable threw plastic conduit surface mounted, then you could use 2.5mm twin and earth flex straight into a switched fuse spur or 2way 40A c/u with 30mA trip depends how much the guy wants to pay. hope this helps
 
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adamh

  • Thread Starter Thread Starter
  • #3
i'd use a 4mm 2core swa on a 20 amp breaker (voltage drop2.1 %) connect the swa to earth at the house cu, 2way cu in the shed with a 16amp breaker for the socket and a 6 for the lights with an earth rod.
 
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iceman

  • Thread Starter Thread Starter
  • #4
you can use an earth rod but i wouldnt bother you only realy need an earth rod if ya supplyin at caravan static etc ;-)
 
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adamh

  • Thread Starter Thread Starter
  • #5
i thought your not supposed to export the earth on a pme system?

just noticed its 30m not 20 so as iceman says its a 6mm
 
Last edited by a moderator:
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Spudnik

  • Thread Starter Thread Starter
  • #6
Dave,

If the sockets in the house are already RCD protected then if there is a socket on the back wall, easiest thing is to spur off the double to a switch fuse spur along side, through wall to steel conduit end box, 4mm SWA into that down the garden to shed.

SWA into metalclad socket and spur down again for the light.
 
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daver

  • Thread Starter Thread Starter
  • #7
Thanks to everyone for your assistance - Much appreciated
 
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ezzzekiel

  • Thread Starter Thread Starter
  • #8
for a single socket and light in a shed i think seperat consumer unit is a little ott, fuse down from house to shed.
 
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spark1

  • Thread Starter Thread Starter
  • #9
If the shed has any extraneous conductive parts...i.e. metallic pipework or any mettalic structure in contact with the ground then it will require Main equipotential bonding back to the M.E.T at the house end..........this would require 10mm2 for a tncs supply, therefore the armoured cable would need to be a minimum of 10mm2.........in such a case consideration would have to be given to making the shed a TT installation and isolating the sheath of the armour at the shed end......6mm2 cable would then suffice


spark1
 
I agree with spark 1; if you have a fault in the house which raises the potential to the mass of earth (the house) then as your shed mass of earth is of a different potential then you could get a shock.:eek: The safest method (but not the cheapest:mad:) is to spike with an RCD at the shed end - no earthing from the house.
 
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Spudnik

  • Thread Starter Thread Starter
  • #11
If the shed has any extraneous conductive parts...i.e. metallic pipework or any mettalic structure in contact with the ground then it will require Main equipotential bonding back to the M.E.T at the house end..........this would require 10mm2 for a tncs supply, therefore the armoured cable would need to be a minimum of 10mm2.........in such a case consideration would have to be given to making the shed a TT installation and isolating the sheath of the armour at the shed end......6mm2 cable would then suffice


spark1
Very rare that a garden shed would have any metal parts that would need bonding.

I also think that whatever size cable was used, if there were extraneous parts in the shed this would need running back as a separate 10mm, in addition to the supply cable.

Therefore, it would make sense to make the shed a TT.

All IMHO.
 
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spark1

  • Thread Starter Thread Starter
  • #12
Jason the cpc and the Main equipotential protective bonding conductor in the distribution circuit to the shed are allowed to be one and the same provided the size satisfies both criteria.....no need for seperate bonding cable ...hence the minimum size usually being 10mm2.


spark1
 
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Spudnik

  • Thread Starter Thread Starter
  • #13
Jason the cpc and the Main equipotential protective bonding conductor in the distribution circuit to the shed are allowed to be one and the same provided the size satisfies both criteria.....no need for seperate bonding cable ...hence the minimum size usually being 10mm2.


spark1
Yes you are right.

However, i was assuming a less than 10mm supply:)
 
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