I need to put a ring main in a small extension to the main house
(currently it has no power). The original outside wall to the house is
a cavity wall, and the flat roof of the extension meets the house wall
below the level of the ground floor ceiling. Floor in both main house
and extension are solid, and all the wiring is above the ceiling therefore.

So how should I get the cables across the cavity and into the extension?
There is no way through other than through the cavity. Should I pass it
through a conduit of some sort to protect it within the cavity? Any
thoughts (including what the regs say on this) much appreciated.

Thanks
David

"Lobster" wrote in message ...
So how should I get the cables across the cavity and into the extension?
There is no way through other than through the cavity. Should I pass it
through a conduit of some sort to protect it within the cavity? Any
thoughts (including what the regs say on this) much appreciated.

IIRC when passing cables through a cavity, you should always pass them
through a conduit of some sort to protect them in the event something should
drop down the cavity and damage them.

Incidentally, I'm sure you're aware that if you're extending your ring main,
or putting in a complete new circuit you have to get it checked by your
local council's building control office now?


--
Best Wishes
Simon (aka Dark Angel)
"Dark Angel's Realm of Horror" - http://www.realmofhorror.co.uk
"Realm of Horror Radio" - http://www.live365.com/stations/313834

"Dark Angel" wrote in message
...

"Lobster" wrote in message ...
So how should I get the cables across the cavity and into the extension?
There is no way through other than through the cavity. Should I pass it
through a conduit of some sort to protect it within the cavity? Any
thoughts (including what the regs say on this) much appreciated.

There was a thread not so long ago that implied that cables run through
cavities did not need to be within 6" of the sides or ceiling, as with
buried
cable. Also, with buried cables, they need to be 50mm deep in a wall if
unprotected, I'm not sure how this relates to cavity walls, if you can keep
the unprotected cables =50mm from the surface this might be OK???

Andy.

andrewpreece wrote:
"Dark Angel" wrote in message
...

"Lobster" wrote in message ...

So how should I get the cables across the cavity and into the extension?
There is no way through other than through the cavity. Should I pass it
through a conduit of some sort to protect it within the cavity? Any
thoughts (including what the regs say on this) much appreciated.


There was a thread not so long ago that implied that cables run through
cavities did not need to be within 6" of the sides or ceiling, as with
buried
cable. Also, with buried cables, they need to be 50mm deep in a wall if
unprotected, I'm not sure how this relates to cavity walls, if you can keep
the unprotected cables =50mm from the surface this might be OK???

Hmm, not sure. Just to clarify, what I'm suggesting has the cables
passing through the cavity perpendicularly; ie, through one leaf, across
the gap at 90 degrees, then through the second leaf.

David

Lobster wrote:
I need to put a ring main in a small extension to the main house
(currently it has no power). The original outside wall to the house is
a cavity wall, and the flat roof of the extension meets the house wall
below the level of the ground floor ceiling. Floor in both main house
and extension are solid, and all the wiring is above the ceiling therefore.

So how should I get the cables across the cavity and into the extension?
There is no way through other than through the cavity. Should I pass it
through a conduit of some sort to protect it within the cavity? Any
thoughts (including what the regs say on this) much appreciated.

Thanks
David

I have had 2 conservatories built, 1 this month. "Pro" sparks wired both.

First the cable bridged the cavity unprotected to get the feed into the
conservatory and was run inside the cavity unprotected.

Second, similar although the walls are rubble filled (more likely for
things to drop eh?).

I am no expert and have no clue about the regs, but realistically whats
going to fall on the cable? insulation? wall tie? snot of mortar?

AIUI most hazardous is the insulation (if EPS ... posted thread a while
back on EPS & cables) ... I asked a spark I know about this and his
opinion was that it would not cause a problem unless the circuit was
seriously loaded causing the cables to heat.

HTH,

Alex.

AlexW wrote:
Lobster wrote:

I need to put a ring main in a small extension to the main house
(currently it has no power). The original outside wall to the house
is a cavity wall, and the flat roof of the extension meets the house
wall below the level of the ground floor ceiling. Floor in both main
house and extension are solid, and all the wiring is above the ceiling
therefore.

So how should I get the cables across the cavity and into the
extension? There is no way through other than through the cavity.
Should I pass it through a conduit of some sort to protect it within
the cavity? Any thoughts (including what the regs say on this) much
appreciated.

Thanks
David


I have had 2 conservatories built, 1 this month. "Pro" sparks wired both.

First the cable bridged the cavity unprotected to get the feed into the
conservatory and was run inside the cavity unprotected.

Second, similar although the walls are rubble filled (more likely for
things to drop eh?).

I am no expert and have no clue about the regs, but realistically whats
going to fall on the cable? insulation? wall tie? snot of mortar?

AIUI most hazardous is the insulation (if EPS ... posted thread a while
back on EPS & cables) ... I asked a spark I know about this and his
opinion was that it would not cause a problem unless the circuit was
seriously loaded causing the cables to heat.

Also same spark I know has just had a conservatory too and put the the
feed through the cavity in that manner (as described in the same
conversation about EPS). He is part peed up with the NCA and all that.
We had had several pints so this info may me err blurred.


HTH,

Alex.

"Lobster" wrote in message
...
I need to put a ring main in a small extension to the main house (currently
it has no power). The original outside wall to the house is a cavity wall,
and the flat roof of the extension meets the house wall below the level of
the ground floor ceiling. Floor in both main house and extension are
solid, and all the wiring is above the ceiling therefore.

So how should I get the cables across the cavity and into the extension?
There is no way through other than through the cavity. Should I pass it
through a conduit of some sort to protect it within the cavity? Any
thoughts (including what the regs say on this) much appreciated.

The easiest way is to drill right though with a 20mm x 300mm masonry drill,
then push a bit of 20mm conduit through the holes. The conduit, being rigid,
will go into the far hole more readily and then you only have one long hole
to feed the cable through.

Colin Bignell

nightjar nightjar@ wrote:
"Lobster" wrote in message
...

I need to put a ring main in a small extension to the main house (currently
it has no power). The original outside wall to the house is a cavity wall,
and the flat roof of the extension meets the house wall below the level of
the ground floor ceiling. Floor in both main house and extension are
solid, and all the wiring is above the ceiling therefore.

So how should I get the cables across the cavity and into the extension?
There is no way through other than through the cavity. Should I pass it
through a conduit of some sort to protect it within the cavity? Any
thoughts (including what the regs say on this) much appreciated.


The easiest way is to drill right though with a 20mm x 300mm masonry drill,
then push a bit of 20mm conduit through the holes. The conduit, being rigid,
will go into the far hole more readily and then you only have one long hole
to feed the cable through.

Sounds good, thanks.

Thinking further on this: presumably this must arise everytime someone
installs an external light fitting where there's a cavity wall. I
wonder how many sparks do anything other than poke the cable straight
through, as others have suggested.

I suppose one issue to consider is what happens if someone wants to
install cavity wall insulation at a later date... if the cable is
unprotected within the cavity, it will likely come into contact with
polystyrene insulation, causing instant disintegration(?) of the outer
sheath...

David

"Lobster" wrote in message
...

I suppose one issue to consider is what happens if someone wants to
install cavity wall insulation at a later date... if the cable is
unprotected within the cavity, it will likely come into contact with
polystyrene insulation, causing instant disintegration(?) of the outer
sheath...

No.
The plasticizer causes the polystyrene to shrink away from the cable so it
breaks contact.
Assuming your polystyrene is bonded together like it should be.

Mines been OK for the last 25 years, I'll let you know if anything happens.

dennis@home wrote:
"Lobster" wrote in message
...

I suppose one issue to consider is what happens if someone wants to
install cavity wall insulation at a later date... if the cable is
unprotected within the cavity, it will likely come into contact with
polystyrene insulation, causing instant disintegration(?) of the
outer sheath...

No.
The plasticizer causes the polystyrene to shrink away from the cable
so it breaks contact.
Assuming your polystyrene is bonded together like it should be.

Mines been OK for the last 25 years, I'll let you know if anything
happens.

Isn't PVC wiring only supposed to be 25 year life anyway?

dennis@home wrote:
"Lobster" wrote in message
...

I suppose one issue to consider is what happens if someone wants to
install cavity wall insulation at a later date... if the cable is
unprotected within the cavity, it will likely come into contact with
polystyrene insulation, causing instant disintegration(?) of the outer
sheath...

No.
The plasticizer causes the polystyrene to shrink away from the cable so it
breaks contact.
Assuming your polystyrene is bonded together like it should be.


Insulation can be small polystyrene beads. They might move to take up
the gap, causing continuous contact.

MBQ

wrote in message
oups.com...

Insulation can be small polystyrene beads. They might move to take up
the gap, causing continuous contact.

That's what I have.
It should be bonded using PVA when its blown into the wall.

Isn't PVC wiring only supposed to be 25 year life anyway?

Where did that come from ?

Dave

AlexW wrote:
snip


Also same spark I know has just had a conservatory too and put the the
feed through the cavity in that manner (as described in the same
conversation about EPS). He is part peed up with the NCA and all that.
We had had several pints so this info may me err blurred.


Ooopss...

ECA not NCA, slip of the fingers, step dad involved with caving you see....


HTH,

Alex.