I always tend to think of conduit as protection against screws and
nails, but clearly it isn't since a nail'd go straight through.

Perhaps cable embedded directly in the plaster could corrode, or
become damaged? But although I've seen plenty of unducted cables in
plaster, they seem to survive ok.

Or perhaps the air gap around the cable helps with temperature
control?

Or perhaps it just encourages neatness.

What's the official reason?

To

PS, a bit late in the day, but I'm very sorry to hear about Andy Hall.
Sadly I didn't get to know him. He gave me lots of good advice on my
occasional visits here. One of the good guys,

"tonyjeffs" wrote in message
...
I always tend to think of conduit as protection against screws and
nails, but clearly it isn't since a nail'd go straight through.

Perhaps cable embedded directly in the plaster could corrode, or
become damaged? But although I've seen plenty of unducted cables in
plaster, they seem to survive ok.

Or perhaps the air gap around the cable helps with temperature
control?

Or perhaps it just encourages neatness.

What's the official reason?

To

PS, a bit late in the day, but I'm very sorry to hear about Andy Hall.
Sadly I didn't get to know him. He gave me lots of good advice on my
occasional visits here. One of the good guys,


Hi,
It is to protect the pvc outer sheathing from limein the plaster.
I thought the same as you.
I asked at Coledge. Was told this from one of my Tutors.

Kind Regards


Micky.. LEEDS.

In article ,
Micky Savage wrote:

"tonyjeffs" wrote in message
...
I always tend to think of conduit as protection against screws and
nails, but clearly it isn't since a nail'd go straight through.

Perhaps cable embedded directly in the plaster could corrode, or
become damaged? But although I've seen plenty of unducted cables in
plaster, they seem to survive ok.

Or perhaps the air gap around the cable helps with temperature
control?

Or perhaps it just encourages neatness.

What's the official reason?

To

PS, a bit late in the day, but I'm very sorry to hear about Andy Hall.
Sadly I didn't get to know him. He gave me lots of good advice on my
occasional visits here. One of the good guys,


Hi,
It is to protect the pvc outer sheathing from limein the plaster.
I thought the same as you.
I asked at Coledge. Was told this from one of my Tutors.


Not quite sure how PVC conduit would protect PVC wiring?

--
*In "Casablanca", Humphrey Bogart never said "Play it again, Sam" *

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

Dave Plowman (News) wrote:

Hi,
It is to protect the pvc outer sheathing from limein the plaster.
I thought the same as you.
I asked at Coledge. Was told this from one of my Tutors.


Not quite sure how PVC conduit would protect PVC wiring?

I'm glad it's not just me thinking that. And how much modrn plaster is
lime based?

Anyway, my home is plastered in lime with added goathair to satisfy the
LBO. Several places have PVC sheathed cable buried beneath the plaster.
Recent work in the kitchen exposed cable that has been buried for 18
years in lime plaster, no sign of deterioration in the T&E sheath.

On Mon, 6 Oct 2008 12:07:59 +0100, (Steve Firth)
wrote:

Dave Plowman (News) wrote:

Hi,
It is to protect the pvc outer sheathing from limein the plaster.
I thought the same as you.
I asked at Coledge. Was told this from one of my Tutors.


Not quite sure how PVC conduit would protect PVC wiring?

I'm glad it's not just me thinking that. And how much modrn plaster is
lime based?

Anyway, my home is plastered in lime with added goathair to satisfy the
LBO. Several places have PVC sheathed cable buried beneath the plaster.
Recent work in the kitchen exposed cable that has been buried for 18
years in lime plaster, no sign of deterioration in the T&E sheath.

Yes I think the lime story is twaddle too. OK if it were to sit in a
bucket of as-yet-unset lime there might be a problem but on a wall the
lime will set and once it has done that it is pretty inert and not
going to affect PVC

Anna

--
Anna Kettle
Lime plaster repair and conservation
Freehand modelling in lime: overmantels, pargeting etc
Tel: ***(+44) *01359 230642
Mob: * (+44) *07976 649862
Please look at my website for examples of my work at:
www.kettlenet.co.uk *

Anna Kettle wrote:

Yes I think the lime story is twaddle too. OK if it were to sit in a
bucket of as-yet-unset lime there might be a problem but on a wall the
lime will set and once it has done that it is pretty inert and not
going to affect PVC

Some of the buckets with self-sealing lids which the coarse stuff we
bought from the local lime center was packed in were PVC. I've had one
standing outside for a couple of years. Again no sign of deterioration
and that's been in contact with wet lime continuously.

Anyway, my home is plastered in lime with added goathair to satisfy
the LBO.

LBO please?

--
Robin

neverwas wrote:

Anyway, my home is plastered in lime with added goathair to satisfy
the LBO.

LBO please?

Listed Buildings Officer

In article ,
tonyjeffs writes:
I always tend to think of conduit as protection against screws and
nails, but clearly it isn't since a nail'd go straight through.

Perhaps cable embedded directly in the plaster could corrode, or
become damaged? But although I've seen plenty of unducted cables in
plaster, they seem to survive ok.

If you're thinking of the capping and oval trunking in
plaster (which isn't quite the same as conduit)...
Holds the cable in place until plastered.
Protects the cable from the plasterer.
Enables the cable to be replaced without replastering.

Or perhaps the air gap around the cable helps with temperature
control?

Actually, the opposite.

Or perhaps it just encourages neatness.

Yes, that too.

What's the official reason?

There's no requirement to use capping/trunking.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

"tonyjeffs" wrote in message
...
I always tend to think of conduit as protection against screws and
nails, but clearly it isn't since a nail'd go straight through.

If you are using steel conduit that screws together you will notice if you
try and nail it.
That sort of conduit replaces the outer sheath on the cables and you can
pull "singles" through.

There are other lightweight conduits in plastic and pressed steel that don't
offer as much protection.
As well as really lightweight stuff like capping that is only there to
protect against a ham fisted plasterer and nothing else.

At least with metal conduit you can now earth it and comply with the 17th
edition without an RCD.

dennis@home coughed up some electrons that declared:



"tonyjeffs" wrote in message
...
I always tend to think of conduit as protection against screws and
nails, but clearly it isn't since a nail'd go straight through.

If you are using steel conduit that screws together you will notice if you
try and nail it.
That sort of conduit replaces the outer sheath on the cables and you can
pull "singles" through.

I believe you can put singles in PVC conduit[1] and trunking (but not
slotted trunking).

[1] I'm not sure about oval conduit in this respect.

What heavy steel conduit (or steel trunking) buys you is compliance with
regulation 522.6.6 (17th) (IIRC, book's at home) regarding protection of
cables - the other options being:

Use MICC or SWA Armoured or Earth Screened to a certain BS (eg XL Shield,
but not FP200;

Bury 50mm below wall surface;

Protect with =30mA RCD (though there may be other reasons you need an RCD
on a particular final circuit)

Steel conduit would need to be earthed too.

There are other lightweight conduits in plastic and pressed steel that
don't offer as much protection.
As well as really lightweight stuff like capping that is only there to
protect against a ham fisted plasterer and nothing else.

That's my understanding too.

At least with metal conduit you can now earth it and comply with the 17th
edition without an RCD.

Indeed, but given the difficulty in working with heavy steel conduit (the
bending, the cutting and the threading) personally I'd look to XL-Shield
type cable as one option and SWA as the other option - it's much easier to
handle.

Cheers

Tim

"Tim S" wrote in message
...
dennis@home coughed up some electrons that declared:



"tonyjeffs" wrote in message
...
I always tend to think of conduit as protection against screws and
nails, but clearly it isn't since a nail'd go straight through.

If you are using steel conduit that screws together you will notice if
you
try and nail it.
That sort of conduit replaces the outer sheath on the cables and you can
pull "singles" through.

I believe you can put singles in PVC conduit[1] and trunking (but not
slotted trunking).

You probably can, I wouldn't, but that's just me being extra cautious.

dennis@home coughed up some electrons that declared:



"Tim S" wrote in message
...
dennis@home coughed up some electrons that declared:



"tonyjeffs" wrote in message

...
I always tend to think of conduit as protection against screws and
nails, but clearly it isn't since a nail'd go straight through.

If you are using steel conduit that screws together you will notice if
you
try and nail it.
That sort of conduit replaces the outer sheath on the cables and you can
pull "singles" through.

I believe you can put singles in PVC conduit[1] and trunking (but not
slotted trunking).

You probably can, I wouldn't, but that's just me being extra cautious.

OK, think I have the regulation, but I'm not qualified so this is open to
interpretation:

IEE Wiring Regs, 17th Ed.

521.10.1: "Non-sheathed cables for fixed wiring shall be enclosed in
conduit, ducting or trunking. This requirement does not apply to a
protective conductor complying with Section 543.

Non-sheathed cables are permitted if the cable trunking system provides at
least the degree of protection IP4X or IPXXD, or if the cover can only be
removed by means of a tool or a deliberate action."

The IP ratings come down to "can't get a 1mm probe in".

BTW - I'm practising looking up regs to order for my upcoming exams, not
being a smartass

Anyway, if you look at it from another angle, the (plastic) conduit or
trunking is taking the place of the sheath, no more and no
less. "Mechanical protection" is a different game and that's where steel
comes in.

It was certainly a method employed in the last university I worked at,
(singles in plastic trunking).

Cheers

Tim

In article
,
tonyjeffs wrote:
I always tend to think of conduit as protection against screws and
nails, but clearly it isn't since a nail'd go straight through.

It wouldn't go straight through *proper* steel conduit.

Perhaps cable embedded directly in the plaster could corrode, or
become damaged? But although I've seen plenty of unducted cables in
plaster, they seem to survive ok.

Indeed - the use of plastic conduit buried in plaster only really serves
to make wire replacement possibly easier. And may also be easier to fix to
the wall before plastering than naked cable.

Or perhaps the air gap around the cable helps with temperature
control?

Or perhaps it just encourages neatness.

What's the official reason?

Dunno.

--
*Proofread carefully to see if you any words out or mispeld something *

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

tonyjeffs wrote:
I always tend to think of conduit as protection against screws and
nails, but clearly it isn't since a nail'd go straight through.

Perhaps cable embedded directly in the plaster could corrode, or
become damaged? But although I've seen plenty of unducted cables in
plaster, they seem to survive ok.

Or perhaps the air gap around the cable helps with temperature
control?

Or perhaps it just encourages neatness.

What's the official reason?


Do you mean conduit or channelling?

I've used channelling before. I use to use galvanised steel channelling and
one set of regs said you could use short lengths of conductive mechanical
protection without earthing it. What do the new regs say?

It was nice to know that if you tried drilling through plaster I was
confident that a drill would stop at a thin sheet of galvanised steel
channelling and though it sad it was effectively outlawed.

"Fred" wrote in message
...


It was nice to know that if you tried drilling through plaster I was
confident that a drill would stop at a thin sheet of galvanised steel
channelling and though it sad it was effectively outlawed.

I don't know what drills you use but mine will go through steel capping as
if it wasn't there.
They go through reinforcing bars in concrete so a bit of tin isn't going to
stop them.

In article ,
dennis@home wrote:
It was nice to know that if you tried drilling through plaster I was
confident that a drill would stop at a thin sheet of galvanised steel
channelling and though it sad it was effectively outlawed.

I don't know what drills you use but mine will go through steel capping
as if it wasn't there.

A standard masonry drill won't - the cutting angles are wrong for steel.

They go through reinforcing bars in concrete so
a bit of tin isn't going to stop them.

--
*All men are idiots, and I married their King.

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

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


It was nice to know that if you tried drilling through plaster I was
confident that a drill would stop at a thin sheet of galvanised steel
channelling and though it sad it was effectively outlawed.

I don't know what drills you use but mine will go through steel
capping as if it wasn't there.
They go through reinforcing bars in concrete so a bit of tin isn't
going to stop them.

That's not my experience. A masonary bit is usually a little worn and
doesn't go through the thinnest of tin without applying a lot of pressure.

What I find most sad if that the MP's daughter may have been save if the
channelling covering the offending wire had been steel, saving us from Part
P. I think the IEE has a lot to answer for.

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


It was nice to know that if you tried drilling through plaster I was
confident that a drill would stop at a thin sheet of galvanised steel
channelling and though it sad it was effectively outlawed.

I don't know what drills you use but mine will go through steel
capping as if it wasn't there.
They go through reinforcing bars in concrete so a bit of tin isn't
going to stop them.

That's not my experience. A masonary bit is usually a little worn and
doesn't go through the thinnest of tin without applying a lot of pressure.

Try these http://www.screwfix.com/prods/99844

Overview, in conclusion:

Conduit doesn't protect against lime attack
-doesn't help with temperature
-doesn't help protect from drills and nails.
-wouldn't be a huge help if you had to replace a lot of cable. You'd
be very lucky to successfully drag a set of new cables through much of
my existing kitchen conduit without snagging on the L s and T s.
Easier for an electrician in the future to rip everything out and
start from scratch.

So it seems that conduit doesn't really serve any great purpose.
-It somehow encourages me to do a neater job though, to keep to the
zones and think things through more carefully. Kinda looks like it
ought to be there. So I'll carry on using it. :-)

Cheers

Tony

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


It was nice to know that if you tried drilling through plaster I
was confident that a drill would stop at a thin sheet of
galvanised steel channelling and though it sad it was effectively
outlawed.

I don't know what drills you use but mine will go through steel
capping as if it wasn't there.
They go through reinforcing bars in concrete so a bit of tin isn't
going to stop them.

That's not my experience. A masonary bit is usually a little worn
and doesn't go through the thinnest of tin without applying a lot of
pressure.

Try these http://www.screwfix.com/prods/99844

Fantastic product. Don't use much else.


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