If electrics are your thing, read on; else there be boring stuff to follow!

Following on from the thread on SWA carrying two circuits, and in
particular the issues raised concerning the actual armour resistivity
rather than just its adiabatic fault withstand capability; I have updated:

http://wiki.diyfaq.org.uk/index.php?...rmour_as_a_CPC

with a new table that includes the armour resistance to facilitate
calculations of earth loop, or equivalence for the purposes of a bonding
conductor. I added 5 core SWA for completeness.

I have temporarily retired the table for 70 deg C PVC clad cable since I
did not have data for the armour resistance, and the cable seems less
commonly available anyway - anyone know of a source of figures? I
suppose we could estimate them based on the total armour area....

I have also explicitly broken out:

http://wiki.diyfaq.org.uk/index.php?...potential_Zone

and reworded it a bit to attempt clarification of the bonding conductor
requirements.

See if that makes any more sense. Feel free to edit comment as appropriate.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

I have also explicitly broken out:

http://wiki.diyfaq.org.uk/index.php?...potential_Zone

and reworded it a bit to attempt clarification of the bonding
conductor requirements.


A question rather than a comment.

We have at present a TN-S supply. (Old lead sheath cable.) Neighbours
with more recent fuses and meters seem to have been converted to TN-C-S
(and that is certainly the norm on new builds locally). Is this
something they do as a matter of course, and can they insist on doing so
despite the knock-on consequences for exported earths or whatever?

It's not a wholly theoretical question as I'll need to get our meter
upgraded to 100A when we get a new kitchen and I *may* one day get
around to building a shed and using something other than a 20m extension
reel.
--
R

neverwas wrote:

We have at present a TN-S supply. (Old lead sheath cable.) Neighbours
with more recent fuses and meters seem to have been converted to TN-C-S
(and that is certainly the norm on new builds locally). Is this
something they do as a matter of course, and can they insist on doing so
despite the knock-on consequences for exported earths or whatever?

Yes, if the service cable has to be replaced for any reason you'll find
that the only earth offered is TN-C-S/PME. You always have the TT
option of course, but in normal circumstances I'd upgrade the main
bonding if necessary and accept PME for the house.

--
Andy