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Just after some clarification of you guys.

My dads asked me to do some lights and sockets in a garage outbuilding he's building 10foot from the house.

It requres 1 lighting circuit 6A, 1 socket radial 20A and a 1 supply for 2 electric gates in the future. Been looking at the amount of power that required for an electric gate of this type, and its generally 5A max. So for 2 I'm going to allow a 16A MCB with 2.5 Swa on the safe side.

With all that in mind. My max demand is 16A plus 26x0.42 = 26.92Amps which means a 4mm swa at a length of 10 meters.

will the garage need TTing for such a small supply, or is it a case of TT everything that is outside the equipotential zone.

 
if its 1 socket radial do it on 16amp mcb or would a 20 amp cover the socket and gates

 
no sorry its one socket circuit with 3 sockets on it, 20a radial

the lighting is 3 single fluorescents inside and 4 outside feature lights on a photocell.

The gates would be on their own circuit.

 
This answers the OP's question thoroughly and concisely! ROTFWL
:D

bit vage and not really what he was looking for.

is it pme in the house if so people will say different things

i dont no a definate answer for exporting pme but i will find out as i know some one who works for central networks and i will ask him

 
some do some don't TT it... its an ongoing argument... personally i prefare to do both( Export earth and TT) ... helps me sleep at night , i know that loads of people will now tell me your not allowed to export earth!!

 
:D bit vage and not really what he was looking for.

is it pme in the house if so people will say different things

i dont no a definate answer for exporting pme but i will find out as i know some one who works for central networks and i will ask him
Glad you took that in the spirit it was meant. Guiness Drink

 
Glad you took that in the spirit it was meant. Guiness Drink
its all good fun. mocking is fun as long as its in good humor:)

 
Just after some clarification of you guys.My dads asked me to do some lights and sockets in a garage outbuilding he's building 10foot from the house.

It requres 1 lighting circuit 6A, 1 socket radial 20A and a 1 supply for 2 electric gates in the future. Been looking at the amount of power that required for an electric gate of this type, and its generally 5A max. So for 2 I'm going to allow a 16A MCB with 2.5 Swa on the safe side.

With all that in mind. My max demand is 16A plus 26x0.42 = 26.92Amps which means a 4mm swa at a length of 10 meters.

will the garage need TTing for such a small supply, or is it a case of TT everything that is outside the equipotential zone.
"or is it a case of TT everything that is outside the equipotential zone"

No IMHO that is definitely not the mindset to approach it by!

you need to ask yourself a couple o basic q's

1/ what is the construction of the outbuilding/garage?

a) Brick / wood (Nonconducting!)

B) Metal frame prefabricate jobbie.....

c) Maybe some parts are conducting & could introduce and earth potential?

2/ Are there any incoming gas / water / oil pipes that could introduce and earth potential?

If possibility of earths and/or loadsa metal bits I would probably TT!

If non condcuting... short run (10m <) export supply from House (inc earth)!

 
Thanks SL.

Its brick with timber roof with no other services. So looks like exporting will be fine.

Why is it, that with other potential paths to earth pose a problem. Is it the fact that in a fault situation the fault current may go to earth in a different way other than through the house CU?

 
yer but i think its only when the supplier losese the nutral

 
Why is it, tha with other potential paths to earth pose a problem. Is it the fact that in a fault situation the fault current may go to earth in a different way other than through the house CU?
Because the 2.5mm earth on the SWA is taking your fault current, and all your neighbours, then it melts!

 
The problems associated with exporting the Earth, only really apply to PME installations.

With PME, the Earth and Neutral are combined. If there is a fault on the supply side of the Neutral, the Earth will then carry the load.

Further with PME installations, the main Earth bonding has to be a minimum of 10mm

 
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