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Garage supply


sellers

Question

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.

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16 answers to this question

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Andy™

dont forget if your usin the armour as the earth, if you intend to use it for equip bonding, you need to get the copper equivalent CSA

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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.

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

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

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Apache

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!

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I wouldn't TT it (but I know others would!), what's the earthing arrangement for the house?

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oh yeah sorry forgot vital info.

TNC-S

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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

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danny7299

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!!

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: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

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Is it still the same with a TNS system?

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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:)

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spinlondon

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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SPECIAL LOCATION
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)!

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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?

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