from head to meter

[buddha]

hi guys,im working on a domestic installation where the head is at the bottom of the basement and it is connected to the meter which is sited at the top of the stairs by the entrance to the basement.They are set apart by a distance of around 5 meters.

The live and neutral conductors from the head to the meter appear to be around 16mm csa and travel inside a metal conduit.

Its a tn-s system and the armoured of the supply cable is joined via temby clamps to the metal conduit with 4mm earth and at the meter end,again a 4mm from conduit to the incoming earth of the distribution board?

surely this is not enough,but wouldnt it have been the local electricity board that put it in? none of the seals at head or meter have been cut.

can anyone shed some light on this,many thanks. bad day explode

 

[Evans Electric]

Sounds about right for an oldish electricity board type job. Don't forget they were never obliged to supply an earth connection ,just a single phase supply at 240v .

I agree that bits of 4mm and a length of conduit don't amount to what is now considered a "good earth connection".

Suggest you ask if a plumbed (TN-S) connection or a TNCS( PME) can be supplied and run a 16mm back.

 

[Badger]

could you not run a seperate earth to the MET at the head?

 

[initforthemoney]

Thats what i was thinking.

Just run a 16mm alongside the tails.

Jobs a good-un

 

[buddha]

nice one guys i'll run a 16mm earth from suppy armoured sheath to dis/board,will 16mm be ok for the live and neutral then?been looking at the books and they just mention the tails from the meter to the board,25mm,you'd have though the head to the meter would have to be the same,i.e 25mm,would you?

 

[m4tty]

What size is the mainfuse mate?

 

[buddha]

its 60 amp matty

 

[vince]

16mm is plenty if you use the adiabatic equation its amazing how small your cpc needs to be we always overkill on the cpc as we do with just about every cable we fit for example in a house with half a dozen or so lights on a circuit we use 1.5mm as standard when 1.0mm is still overkilling

 

[buddha]

cheers