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

In article ,
TheScullster wrote:
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.

If those are truly the only options it makes me wonder what planet these
'legislators' are on.

A leakage operated device is often bad news for anything with certain
types of heating elements

Proper steel conduit is expensive and requires skill and special tools to
install.

Chasing two inches into the average wall for a whole cable run will likely
weaken it.

--
*El nino made me do it

Dave Plowman London SW
To e-mail, change noise into sound.

TheScullster wrote:
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.

4 Use a cable with integral earth shield (including SWA or MICC for example)

(1 would be the obvious choice in many cases)

So, the question is, is option 3 above actually directed at modern domestic
installations where the inner leaf is only 100mm thick?

Its not ideal in many if not most cases.


--
Cheers,

John.

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

"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.

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.

"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.


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. ;-)

TheScullster wrote:

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.

4 Fix cable to wall using cable clips, so it will be unseen when the
kitchen units are fitted, routing it to the isolation switch without
being unsightly might be a challenge.

"Andy Burns" wrote

TheScullster wrote:

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.

4 Fix cable to wall using cable clips, so it will be unseen when the
kitchen units are fitted, routing it to the isolation switch without being
unsightly might be a challenge.

Having a solid floor means the cable is coming down from the ceiling, so
unfortunately your suggestion is a non-starter.

Phil

TheScullster wrote:
"Andy Burns" wrote

TheScullster wrote:

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.
4 Fix cable to wall using cable clips, so it will be unseen when the
kitchen units are fitted, routing it to the isolation switch without being
unsightly might be a challenge.

Having a solid floor means the cable is coming down from the ceiling, so
unfortunately your suggestion is a non-starter.

Phil


Well maybe not.

I had a similar situation, although my walls were plasterboard over ply
But one wall was distinctly 'bent' such that a worktop didnt really fit
flush against it, and neither did the eye level cupboards..

The answer was to instal the cupboards and units with an ugly gap, and
then I made a false wall between them with vertical battens and covered
it in 12mm MDF. I was going to tile it, but painted it and its still
that way.

cables run behind that..clipped to the wall behind.

All I lost was about an inch and a half of worktop.

The Natural Philosopher wrote:

The answer was to instal the cupboards and units with an ugly gap, and
then I made a false wall between them with vertical battens and covered
it in 12mm MDF. I was going to tile it, but painted it and its still
that way.

cables run behind that..clipped to the wall behind.

But wouldn't that make them subject to the new 17th edition rules if the
work was being done now?

--
Mike Clarke

"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. :-)

"BigWallop" wrote in message
om...

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.

The latest regulations require specific protection, the metal capping isn't
it.


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?

Do normal people use sds drills or multi-construction bits?
Either will go through the metal capping without you noticing.


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.

No it doesn't.
Masonry nails are hardened steel and will just go straight through.


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.

The new regs assume all areas are prone to damage.


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.

Its not to protect the cable, its not expected to survive, however the
person doing it is protected.


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. :-)

In article ,
TheScullster writes
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

Is this the case if the cable is in the "safe zone" (i.e.
horizontally/vertically in line with switch)?

Martin
--
Martin Carroll

"The Natural Philosopher" wrote in message
...
TheScullster wrote:
"Andy Burns" wrote

TheScullster wrote:

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.
4 Fix cable to wall using cable clips, so it will be unseen when the
kitchen units are fitted, routing it to the isolation switch without
being unsightly might be a challenge.

Having a solid floor means the cable is coming down from the ceiling, so
unfortunately your suggestion is a non-starter.

Phil
Well maybe not.

I had a similar situation, although my walls were plasterboard over ply
But one wall was distinctly 'bent' such that a worktop didnt really fit
flush against it, and neither did the eye level cupboards..

The answer was to instal the cupboards and units with an ugly gap, and
then I made a false wall between them with vertical battens and covered it
in 12mm MDF. I was going to tile it, but painted it and its still that
way.

cables run behind that..clipped to the wall behind.

All I lost was about an inch and a half of worktop.

One good place I found for bringing an extra cable down from above in my
kitchen was just behind one of the "decor end panels" on the upper
cupboards. I just put it forward a little bit (may have trimmed a tiny bit
off the rear but TBH don't remember doing that) and that creted a little
channel that a (lighting) cable or two could slip down. Might be a bit of a
squeeze for a fat 6mm2 or 10mm2 cable but it avoided doing anything drastic
when I realised I needed a bit more under-cupboard lighting after nearly
finishing the kitchen.

Regards,
Simon.

dennis@home wrote:

"BigWallop" wrote in message
om...

[snip]

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.

No it doesn't.
Masonry nails are hardened steel and will just go straight through.

I agree with Dennis there. A while ago I needed to re-route a length of old
cable covered by metal capping under plaster. As I excavated plaster along
it's length I could see it was heading ominously for a picture hook on the
wall. Sure enough the pin for the hook had been hammered in straight
through the metal capping and the cable. Subsequent examination of the
cable showed that the pin went straight through the live conductor of the
old 7/.029 T&E with 4 strands one side of the pin and three the other. The
odd thing is that it had been like that for years without causing any
trouble.

--
Mike Clarke

dennis@home wrote:


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.

I was thinking about those multi material drills, they will drill steel
quite effectively - certainly would go through metal capping easily enough.


--
Dave - The Medway Handyman
www.medwayhandyman.co.uk

"The Medway Handyman" wrote in message
om...
dennis@home wrote:


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.

I was thinking about those multi material drills, they will drill steel
quite effectively - certainly would go through metal capping easily
enough.

Dave - The Medway Handyman


I thought we were talking about a cable that is being covered by wall units
and probably tile between worktop and wall units. For a situation like
that, then a cover to stop small picture nails is surely enough protection.

It's not a cable in the middle of a bare wall, where someone is going to
come along and start banging holes through to put up shelves and the like.
The wall units will be probably be covering most of the cable run, and the
space exposed above the units will probably not have anything other than
boxes or ornaments in it, on top of the kitchen units.

Or you could use this stuff
http://www.boddingtons-ltd.com/civil...rning-tape.htm to really
make sure the kitchen fitters don't have an accident. :-)

TheScullster wrote:

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.

There's guidance in the On-Site Guide about the maximum depth of chases.
The depth of vertical chases shouldn't exceed one-third of the wall
(leaf) thickness. For horizontal chases the max. depth is one-sixth of
same.

Using a 30 mA RCBO is unlikely to give any problems if the cooker's in
good condition (although actually fitting one in an older CU might). If
you really want to use a non-protected circuit, the only practical
options in most cases a

- surface wiring, where acceptable;

- use a cable to BS 8436 - Earthshield or Flexishield (with these the
OPD must be a Type B MCB meeting energy limiting class 3), or MICC cable
if you have the skills to install it.

--
Andy

In article ,
TheScullster writes
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.

Asked the question further down the thread but didn't get a reply!

Why does the cable have to be buried if it runs in the zone vertically
or horizontally from the cooker switch?

Cheers
--
Martin Carroll

In article , Martin Carroll
writes
In article ,
TheScullster writes
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.

Asked the question further down the thread but didn't get a reply!

Why does the cable have to be buried if it runs in the zone vertically
or horizontally from the cooker switch?

What I meant to say was why should it be buried 50mm below surface?

Cheers
--
Martin Carroll

Martin Carroll wrote:

What I meant to say was why should it be buried 50mm below surface?

To circumvent the 17th edition requirement that concealed cables have
"Additional protection" from a = 30mA trip RCD. (protecting the cable
(metal conduit etc), using shielded cable (SWA, Earthshield, MICC, etc),
and surface wiring being other ways.

--
Cheers,

John.

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

"John Rumm" wrote in message
et...
Martin Carroll wrote:

What I meant to say was why should it be buried 50mm below surface?

To circumvent the 17th edition requirement that concealed cables have
"Additional protection" from a = 30mA trip RCD. (protecting the cable
(metal conduit etc), using shielded cable (SWA, Earthshield, MICC, etc),
and surface wiring being other ways.

IMO putting it 50 mm deep is a problem.
If you are putting something substantial up you will use screws that are
longer than 50 mm so it offers little protection.
It does make it harder to locate using a detector.
I expect its another of those "we haven't really thought this through but it
sounds like we are doing our job" things the IEE comes up with periodically.
I suppose they will try and ban screws longer than 50 mm to fix the problem.

In article ,
dennis@home wrote:


"John Rumm" wrote in message
et...
Martin Carroll wrote:

What I meant to say was why should it be buried 50mm below surface?

To circumvent the 17th edition requirement that concealed cables have
"Additional protection" from a = 30mA trip RCD. (protecting the cable
(metal conduit etc), using shielded cable (SWA, Earthshield, MICC,
etc), and surface wiring being other ways.

IMO putting it 50 mm deep is a problem. If you are putting something
substantial up you will use screws that are longer than 50 mm so it
offers little protection. It does make it harder to locate using a
detector. I expect its another of those "we haven't really thought this
through but it sounds like we are doing our job" things the IEE comes
up with periodically. I suppose they will try and ban screws longer than
50 mm to fix the problem.

Y es - it's a strange distance. Far more than needed to protect from a
picture hook nail.

Although most things you buy which are designed for screwing to a wall
come with screws which are far too short to make a really secure fixing.

--
*Bigamy is having one wife too many - monogamy is the same

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" wrote in message
...
In article ,
dennis@home wrote:


"John Rumm" wrote in message
et...
Martin Carroll wrote:

What I meant to say was why should it be buried 50mm below surface?

To circumvent the 17th edition requirement that concealed cables have
"Additional protection" from a = 30mA trip RCD. (protecting the cable
(metal conduit etc), using shielded cable (SWA, Earthshield, MICC,
etc), and surface wiring being other ways.

IMO putting it 50 mm deep is a problem. If you are putting something
substantial up you will use screws that are longer than 50 mm so it
offers little protection. It does make it harder to locate using a
detector. I expect its another of those "we haven't really thought this
through but it sounds like we are doing our job" things the IEE comes
up with periodically. I suppose they will try and ban screws longer than
50 mm to fix the problem.

Y es - it's a strange distance. Far more than needed to protect from a
picture hook nail.

Although most things you buy which are designed for screwing to a wall
come with screws which are far too short to make a really secure fixing.

Some of the walls in my house are dry lined.
they have a gap behind the plaster board that can be 50 mm.
That means the cables are 50 mm from the surface and meet the requirements
if they are dropped down and tacked to the wall.
However it offers zero protection as I have to use long screws (120 mm
usually) to get into the wall to fix almost anything.