"dennis@home" wrote in message
...
"BigWallop" wrote in message
om...
"TheScullster" wrote in message
. uk...
Hi all
I have been considering how to satisfy 17th Edition wrt cooker cable.
As I see it there are three options:
1 Fit RCBO in place of MCB for cooker feed
2 Use earthed steel conduit protection
3 Bury cable 50mm below wall surface.
That got me to thinking about the stability of the wall if option 3 is
used.
Allowing for plaster covering, but also the cable thickness means you
will
be chasing to a depth of half the inner leaf thickness.
Also, with cable coming from above, the chase will extend 1/2 to 3/4
the
height of one storey.
So, the question is, is option 3 above actually directed at modern
domestic
installations where the inner leaf is only 100mm thick?
In the case of my kitchen, the inner blocks actually have an insulation
filled cavity "within" the block itself. So the effect of chasing to
50mm
depth (and into this cavity) is even more damaging.
Phil
There are already products
http://www.sparkyselectrical.co.uk/i...ing25wide.html
that have been around since cables were first buried under plaster. Cut
your chase to brick depth and fix your cable. Place the metal capping
over
it with a few wide head nails at the edges (or drill and screw it), just
to
hold it in place until you make good the plaster work.
If you really want to fulfill every regulation in the book, then you can
drill one end of the capping and fix an earth bond from it to the new
socket
/ appliance point. But that is not absolutely needed. All you really
want,
is to stop anyone banging a nail through the cable, which the capping
has
already been designed to do.
No it isn't.
Its just to stop the plaster's float damaging it.
It offers *no* protection against nails or multi-construction drills.
The plastic stuff is cheaper and does the same job.
Am I missing the point? Sorry, but from what I am reading above, the cable
needs protected down a wall, under the plaster. Unless you are a complete
moron, that goes banging holes in walls with chisels and drills willy nilly
into all parts of the building without checking first. Then a piece of
cable capping is enough protection to stop a picture nail from being
hammered through the cable.
In fact, if you are drilling into a wall, you would normally use a masonry
bit in the pistol. A masonry bit is more likely to bend the capping before
it breaks through, which, to a normal person, gives warning because of the
sudden resistance against drill. We are talking about normal people, aren't
we?
The capping is also better detected by devices meant to check the area you
are about to drill into. No one said it protects the cabling from nuclear
attack, but it does offer enough protection from someone banging a nail
through it.
If the cable is in an area prone to damage through exposure to morons, then
either fix it surface to make it completely obvious that the cable is where
it is. Or fix it surface inside a trunk to make it obvious that things
should not be bashed through it.
If you have a cable that needs full protection from all types of
environments, then you would have to find a very special type of cable.
You could break through the inner skin and fish the cable through the
cavity, under / behind the block / brick that you don't want to cut chunks
out of.
But I thought we were talking normal. My apologies again.
And it's a lot cheaper in the long run, because you're not going to all
the
trouble of trying to fix the other options you talk about above.
Have a look in your local wholesaler for it.
Do tell him what its for, they like a laugh occasionally. ;-)
I like to have a good relationship with my suppliers. :-)