Hello,

What is the best way to chase walls for cabling? I read the wiki FAQ
and it talks about making two lines with an angle grinder and then a
bolster chisel to knock out the bit between. That's what I have been
doing. I am using a 115mm angle grinder which is cutting about an inch
into the wall. That's as far as it will go. It's cutting about 10mm of
plaster and 15mm of breeze block. Is that deep enough or do I need to
use a chisel to go deeper?

The angle grinder is making some nice deep lines, but I am not getting
a clean cut of the gap between the lines. The breeze block is very
rough. What is the best way to get a smooth finish? Do I need to
sharpen the chisel? Could it be blunt?

What is the best thing to drop the cable in? Wickes & Screwfix sell
some channeling, which is a bit like a gutter. The problems I see with
this a
1. plaster could get round the back and onto the cables or block the
channel
2. the wire could scrape against the rough surface of the wall

Wickes also sell the same in metal. I guess the metal offers more
protection against drilling/nailing through the cable but does it have
to be earthed? If it became live I cans see that could be very
dangerous.

I see the wiki uses proper conduit, which would avoid both of my
problems above, but if it is 20mm in diameter, it would only be 5mm
beneath the surface. Would that be deep enough? How do you hold it in
place whilst the plaster sets around it?

Thanks,
Sam.

"Sam" wrote in message
...
Hello,

What is the best way to chase walls for cabling? I read the wiki FAQ
and it talks about making two lines with an angle grinder and then a
bolster chisel to knock out the bit between. That's what I have been
doing. I am using a 115mm angle grinder which is cutting about an inch
into the wall. That's as far as it will go. It's cutting about 10mm of
plaster and 15mm of breeze block. Is that deep enough or do I need to
use a chisel to go deeper?

The angle grinder is making some nice deep lines, but I am not getting
a clean cut of the gap between the lines. The breeze block is very
rough. What is the best way to get a smooth finish? Do I need to
sharpen the chisel? Could it be blunt?

What is the best thing to drop the cable in? Wickes & Screwfix sell
some channeling, which is a bit like a gutter. The problems I see with
this a
1. plaster could get round the back and onto the cables or block the
channel
2. the wire could scrape against the rough surface of the wall

Wickes also sell the same in metal. I guess the metal offers more
protection against drilling/nailing through the cable but does it have
to be earthed? If it became live I cans see that could be very
dangerous.

I see the wiki uses proper conduit, which would avoid both of my
problems above, but if it is 20mm in diameter, it would only be 5mm
beneath the surface. Would that be deep enough? How do you hold it in
place whilst the plaster sets around it?

Thanks,
Sam.

Buy a sall cheap circular saw and change the blade for a masonry one you can
then set the depth what you like and at the same tie have a flat edge to
glide up the wall and also connect a hoover to it.. ;-)

Sam wrote:

What is the best way to chase walls for cabling? I read the wiki FAQ
and it talks about making two lines with an angle grinder and then a
bolster chisel to knock out the bit between. That's what I have been

It works, but only if you like dust!

One of the proper wall chasing machines that uses two angle grinder
blades and has a housing to control the dust is better.

doing. I am using a 115mm angle grinder which is cutting about an inch
into the wall. That's as far as it will go. It's cutting about 10mm of
plaster and 15mm of breeze block. Is that deep enough or do I need to
use a chisel to go deeper?

Plenty deep enough. If you use oval conduit for the cables you only 10mm
of depth or so for the conduit.

The angle grinder is making some nice deep lines, but I am not getting
a clean cut of the gap between the lines. The breeze block is very
rough. What is the best way to get a smooth finish? Do I need to
sharpen the chisel? Could it be blunt?

You don't really need a smooth finish - as long as the trunking can sit
in the chase deep enough to get covered up later, you should be ok.


What is the best thing to drop the cable in? Wickes & Screwfix sell
some channeling, which is a bit like a gutter. The problems I see with
this a
1. plaster could get round the back and onto the cables or block the
channel
2. the wire could scrape against the rough surface of the wall

This is capping - only really any use for protecting cables prior to
plastering. Not much use for your application.

Wickes also sell the same in metal. I guess the metal offers more
protection against drilling/nailing through the cable but does it have
to be earthed? If it became live I cans see that could be very
dangerous.

The thin metal stuff offers little more protection against nailing etc
than the plastic. The main benefit is that it stays where you bend it a
little better.

I see the wiki uses proper conduit, which would avoid both of my

What this one?:

http://wiki.diyfaq.org.uk/index.php?title=Wall_chaser

problems above, but if it is 20mm in diameter, it would only be 5mm
beneath the surface. Would that be deep enough? How do you hold it in
place whilst the plaster sets around it?

If you use the oval 22mm conduit:

http://www.tlc-direct.co.uk/Products/MTOV20.html

the depth is only 11mm

You can hold it in place with a blob of bonding plaster or gripfil etc.
Even just a couple of large head clout nails.



--
Cheers,

John.

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

Thanks. I have returned the channeling and have exchanged it for the
oval conduit. How does this affect the rating of the T&E?

I looked at the URL you gave for the wiki and that's not the page I
found. I must have found a different DIY site (via google).

I read some old posts about the Aldi wall chaser. Now that people have
had time to play with them, what were your experiences?

Sam wrote:

Thanks. I have returned the channeling and have exchanged it for the
oval conduit. How does this affect the rating of the T&E?

It reduces it a little, but not much. Column C is the normal figure for
"clipped direct" or a cable buried directly in plaster. Using conduit
results in de-rating to the figures shown in column A. So 2.5mm T&E
drops from 27A to 23A

http://wiki.diyfaq.org.uk/index.php?title=Cables#T.26E

I looked at the URL you gave for the wiki and that's not the page I
found. I must have found a different DIY site (via google).

Thought that may be the case since our one probably answered your
question! ;-)

I read some old posts about the Aldi wall chaser. Now that people have
had time to play with them, what were your experiences?

Not tried the aldi one. I have a Sparky one, which is ok, and does a
good job of eliminating the dust. Has slightly awkward handling though.

--
Cheers,

John.

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

wrote:
On 19 Aug,
John Rumm wrote:

It reduces it a little, but not much. Column C is the normal figure for
"clipped direct" or a cable buried directly in plaster. Using conduit
results in de-rating to the figures shown in column A. So 2.5mm T&E
drops from 27A to 23A

And then you stick two cables in and it drops to 19.5, just below what is
necessary for a ring.

Two smaller conduits solve that problem, and are often easier to thread
anyway.

--
Cheers,

John.

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

On Wed, 20 Aug 2008 02:55:39 +0100, John Rumm
wrote:

Two smaller conduits solve that problem, and are often easier to thread
anyway.

Thanks for the link to the table. Where do you get the figure for
running two or more cables in the same conduit? I was going to run two
separate conduits anyway; partly because I hadn't seen wide conduit in
the shops and partly because like you, I think it would be easier to
push two wires down two separate conduits anyway. Do the regs. say
that the two conduits must be a certain distance apart? Do I have to
chase two separate channels or can I place them together in one wide
channel (the latter would be less work!)

One final question: our house does not have a hall, so you have to
walk from the stairs through the lounge through the dining room to the
kitchen. There are is one light switch at the stair end of the lounge
and one at the kitchen end of the dining room but nothing in between.
I would like to fit two-way switches between the lounge and dining
room. These would be either side of the same (breeze block) wall. I am
concerned if I chased a channel on either side of the wall, I would
effectively be removing twice the depth and would this weaken the
wall? Even if I offset the two channels, I wonder whether the effect
might be the same because they were so close? Is it that you are
allowed to remove one third the depth safely?

I wondered whether I should chase one channel on one side of the wall
to carry both wires and then drill a hole through the wall to take the
second wire to the other switch. Is this acceptable?

Thanks,
Sam.

On Wed, 20 Aug 2008 02:55:39 +0100, John Rumm
wrote:

wrote:
On 19 Aug,
John Rumm wrote:

It reduces it a little, but not much. Column C is the normal figure for
"clipped direct" or a cable buried directly in plaster. Using conduit
results in de-rating to the figures shown in column A. So 2.5mm T&E
drops from 27A to 23A

And then you stick two cables in and it drops to 19.5, just below what is
necessary for a ring.

Two smaller conduits solve that problem, and are often easier to thread
anyway.


I wonder if you can help me? I have a socket that is halfway up the
wall and I would like to lower it to a more sensible level. The wires
to this socket are run in the metal capping you describe. I am
concerned because both wires are run together and having read the
above post it sounds as though the cables are rated at 19.5A "below
what is necessary for a ring".

When I lower the socket would it be a good idea to remove the capping
and replace it with two conduits? If this one socket is like this, I
suppose the rest of the house is. Should I be alarmed?

When you say the cable rating drops from 27A to 19A, does this mean
the rating of the whole ring drops, or just that section?

Thanks,
Stephen.

"Sam" wrote in message
...
Hello,

What is the best way to chase walls for cabling? I read the wiki FAQ
and it talks about making two lines with an angle grinder and then a
bolster chisel to knock out the bit between. That's what I have been
doing. I am using a 115mm angle grinder which is cutting about an inch
into the wall. That's as far as it will go. It's cutting about 10mm of
plaster and 15mm of breeze block. Is that deep enough or do I need to
use a chisel to go deeper?

The angle grinder is making some nice deep lines, but I am not getting
a clean cut of the gap between the lines. The breeze block is very
rough. What is the best way to get a smooth finish? Do I need to
sharpen the chisel? Could it be blunt?

What is the best thing to drop the cable in? Wickes & Screwfix sell
some channeling, which is a bit like a gutter. The problems I see with
this a
1. plaster could get round the back and onto the cables or block the
channel
2. the wire could scrape against the rough surface of the wall

Wickes also sell the same in metal. I guess the metal offers more
protection against drilling/nailing through the cable but does it have
to be earthed? If it became live I cans see that could be very
dangerous.

I see the wiki uses proper conduit, which would avoid both of my
problems above, but if it is 20mm in diameter, it would only be 5mm
beneath the surface. Would that be deep enough? How do you hold it in
place whilst the plaster sets around it?

I just used normal trunking and screwed it into the chased wall. Inserted
the cables and then clipped the lid onto the trunking. This was firm enough
to plaster over.

Steven.

On Mon, 18 Aug 2008 23:26:04 +0100, "Steven Campbell"
wrote:

I just used normal trunking and screwed it into the chased wall. Inserted
the cables and then clipped the lid onto the trunking. This was firm enough
to plaster over.

That's fine as long as you remember that the cable is effectively
buried. Right angle bends in trunking will make it virtually
impossible to 'cut and draw' to replace a cable.

--
Frank Erskine