CU 15m away from meter

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PIP IOM

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Hi again all,

I am currently refurbing/rewiring an old cottage/outbuildings/new extension etc etc.

The meter box is outside and i want our CU in a cupboard 15m away.

It is a TT system and the rod is below the meter box outside.

I have read a few historic threads and am thinking the Click 80amp sw/f is best option back to back with meter (in a small cupbd dead handy)

Then either 25mm tails or armoured through building to CU (noticed divided opinions on tails 15m)

Firstly.

Do I still need a 100ma TD RCD to cover the tails/armd (they will be in floor space and 1 safe zone rising from CU) As in 16th edition.

Secondly where do I put the MET ie do I take 16mm G/Y from rod to near CU or can input/output it from 80a SW/F (prefer to take bonding back to CU if poss.)

Sorry for long story

 
I would think td RCD is necessary if you are using swa to protect cable. Tails you could probably get away with not using one but personally I think swa is best option. I would think RCD would be needed before switch fuse although they are insulated but it would then protect whole installation. Shame it's TT really.

 
Tails you could probably get away with not using one but personally I think swa is best option.
as its TT, it would require RCD regardless of cable. and if you use tails, then it would probably need to be 30mA if its chased etc

 
As its TT you will have to RCD protect it 100mA TD RCD then use 30mA RCD at C/U CJS

 
no prob with you using a 80A S/F but you also need to protect with 100mA RCD,

so why not use a little 1 way CU with an 80A MCB.?

no opinion as to whether you use SWA or tails, MEA wont be bothered either way, Ive done both in the past, although for 15m SWA may be a more prudent choice.

as for MET, remember if you put it at/near SF then you need to get your MEBs there as well,

best to put it close to CU if possible, it makes life easier in the long run.

@Batty,

once out of Douglas or Ramsey most of the Isle of Man is TT, and unfortunate of you to say unfortunately,

why.?

TT is by far the safest earthing system to be had if installed and maintained correctly.

where abouts you working Pip.?

you may have issues around Laxey due to the sheer amount of slate, I had to drive 3 rods in once, and 5 in Maughold for the same reason, extendable rods only work till you hit the slate bed, then they simply wont drive any more.

 
no prob with you using a 80A S/F but you also need to protect with 100mA RCD,so why not use a little 1 way CU with an 80A MCB.?

no opinion as to whether you use SWA or tails, MEA wont be bothered either way, Ive done both in the past, although for 15m SWA may be a more prudent choice.

as for MET, remember if you put it at/near SF then you need to get your MEBs there as well,

best to put it close to CU if possible, it makes life easier in the long run.

@Batty,

once out of Douglas or Ramsey most of the Isle of Man is TT, and unfortunate of you to say unfortunately,

why.?

TT is by far the safest earthing system to be had if installed and maintained correctly.

where abouts you working Pip.?

you may have issues around Laxey due to the sheer amount of slate, I had to drive 3 rods in once, and 5 in Maughold for the same reason, extendable rods only work till you hit the slate bed, then they simply wont drive any more.
Only for the fact you have to RCD protect supply but should only be a few pounds on the job.

 
Only for the fact you have to RCD protect supply but should only be a few pounds on the job.
a few quid shouldn't come into play when its the safest earthing system we are legally allowed to use in the UK.

so why you say shame its TT.?

or is that just an oversight due to money.?

 
a few quid shouldn't come into play when its the safest earthing system we are legally allowed to use in the UK.so why you say shame its TT.?

or is that just an oversight due to money.?
I think we will always disagree on earthing systems personally if DNO supply an earth I will use it.

 
Cheers guys

This is our future home so cost does'nt come into it re safety, I was just a bit confused (as usual) re the requirement 30ma/11ma - tails/SWA -MET siting.

It is looking like a 3core 25mm SWA (potential future holiday let chalet/aptmnt fed from main CU so 16mm not enough) from small CU back to back with outside box.

I take it is SWA into adaptable box cores through to small CU (main earth jointed in adaptable box?

Appreciate both views on TT, the key remark is installed/tested correctly.

With there being no testing/certing at all over here until recently virtually every TT job you need to price has to have the, if the earth/bonding is OK, clause built in. I always test a few Zs but parallel paths can make it hit and miss.

Virtually every job will have just had a rod belted in and connected.

 
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