replaceing consumer unit in shed (with no earth)

[Avidude]

hi i am looking to take my napit exam.
i want to replace a garage consumer unit,
i have looked and found that it is using the swa as the earth (2 core swa)
what can i do?
can i use the swa as the earth for the new consumer unit?
i don't want to have to use a TT system.
thanks for any input
avidude

 

[telectrix]

what size SWA. and can you get a Ze reading from the garage end? might be better to make sure the SWA armour is earthed at the house end only, then TT the garage. That way you will only be assessed on your work in the garage. be sure to RCD/RCBO both circuits.

 

[Avidude]

Hello
the swa is only 2.5 2 core,
i fond that the swa was not even connected at the board (So there was no earth)
i have never worked with tt system before.
where can i find out where to buy and how to use earth rods?

 

[Guest123]

What type of earthing system is present in the house???

 

[telectrix]

i.d start by replacing the SWA. 6mm at least, maybe 10mm, depends on your load.

 

[ezzzekiel]

any wholesaler will sell you a rod and clamp for about £10, just knock the rod into the ground fit the clamp on the end and tie your earth to it.

alternatively run a seperate earth from the met to the garage (exporting of earths may or may not be an issue)

 

[Avidude]

it is a tns system

 

[dsb electrical]

welcome to napit i am also a napit memeber 12428 i agree with telectrix as a tt would remove any doubts this was mentioned in the napit main forum a while back and will make it more simple to pass

 

[Avidude]

I think that it is a good idea to use earth rods,, is there any way that i can get away with using the 2.5mm swa 2 core cable to save me from digin up the whole garden?

 

[Guest123]

As it's a TN-S system, using the armour as the CPC is totally acceptable.

Make the SWA a 20A radial circuit from the house CU and install a garage CU at the garage end. Most likely it will come with a 40A 30mA RCD, & 1 x 16A & 1 x 6A MCB's.

Make sure the SWA is glanded correctly at both ends and there wont be an issue.

 

[telectrix]

as both previous posts. earth rod,(missing drains etc) drill concrete floor, whack it in, no aggro with exsported earth, connection in proper box and flagged with safety earth blah, blah tag., 10mm G/Y in pvc tube to CU. nice job.

 

[Guest123]

Why all the additional work though???

 

[Avidude]

thanks so much for all your input.
do i need to rcbo the swa from the house to the shed?

 

[Amp David]

Some questions are making me think are you actually ready for a NAPIT inspection yet

 

[Amp David]

As it's a TN-S system, using the armour as the CPC is totally acceptable.

Make the SWA a 20A radial circuit from the house CU and install a garage CU at the garage end. Most likely it will come with a 40A 30mA RCD, & 1 x 16A & 1 x 6A MCB's.

Make sure the SWA is glanded correctly at both ends and there wont be an issue.

This is what i'd be doing too.