Finally got round to looking at the upstairs lights in this place, and discovered that all the chased-in cable uses 15mm copper as conduit containing 1 or 2 1.5mm cables (well, could be 1.0)

My understanding is that this doesn't need earthing (it isn't) because it contains normal T+E, so double insulated.

My concern is that when I pull new cable through it, I run the risk of damaging it, particularly if I'm running two cables. I can deburr as much as possible - it's already deburred - and tape over the edges - but is there anything else to help matters?

On Sunday, 4 April 2021 at 12:00:47 UTC+1, Ben Blaukopf wrote:
Finally got round to looking at the upstairs lights in this place, and discovered that all the chased-in cable uses 15mm copper as conduit containing 1 or 2 1.5mm cables (well, could be 1.0)

My understanding is that this doesn't need earthing (it isn't) because it contains normal T+E, so double insulated.

My concern is that when I pull new cable through it, I run the risk of damaging it, particularly if I'm running two cables. I can deburr as much as possible - it's already deburred - and tape over the edges - but is there anything else to help matters?

Metal capping does not need an earth so I guess the pipe would not either, but you need more expert advice. You may run into problems if using 3core + earth for two way lighting and if you are planning to loop in at the switches the pipe is woefully inadequate. If you have loft insulation and the cables will run either across or through it you may have to uprate the cable to 1.5mm2 which make for a tighter fit.

Richard

Are you worried about the insides of corners etc? How is it assembled at
corners, surely not like a water pipe with fittings? I don't think I've ever
come across this sort of thing, most conduits I've seen are jointed black
painted tubes with a thread on the end which is often not used for fixing it
seems. Brian

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"Ben Blaukopf" wrote in message
...
Finally got round to looking at the upstairs lights in this place, and
discovered that all the chased-in cable uses 15mm copper as conduit
containing 1 or 2 1.5mm cables (well, could be 1.0)

My understanding is that this doesn't need earthing (it isn't) because it
contains normal T+E, so double insulated.

My concern is that when I pull new cable through it, I run the risk of
damaging it, particularly if I'm running two cables. I can deburr as much
as possible - it's already deburred - and tape over the edges - but is
there anything else to help matters?

On 04/04/2021 15:34, Brian Gaff (Sofa) wrote:
Are you worried about the insides of corners etc? How is it assembled at
corners, surely not like a water pipe with fittings? I don't think I've ever
come across this sort of thing, most conduits I've seen are jointed black
painted tubes with a thread on the end which is often not used for fixing it
seems. Brian

Copper would be a lot easier to bend. I have bent steel conduit, but it
is very hard work.

On Sunday, 4 April 2021 at 15:34:12 UTC+1, Brian Gaff (Sofa) wrote:
Are you worried about the insides of corners etc? How is it assembled at
corners, surely not like a water pipe with fittings? I don't think I've ever

It's been used like the plastic oval stuff - straight runs in plaster. No corners.

Experimentation in the garage says 2x1.5mm T+E just about fits, and a single three core is easy - provided that the cut end is reamed out properly.

In article , Steve Walker
wrote:
On 04/04/2021 15:34, Brian Gaff (Sofa) wrote:
Are you worried about the insides of corners etc? How is it assembled
at corners, surely not like a water pipe with fittings? I don't think
I've ever come across this sort of thing, most conduits I've seen are
jointed black painted tubes with a thread on the end which is often not
used for fixing it seems. Brian

Copper would be a lot easier to bend. I have bent steel conduit, but it
is very hard work.

not with a proper bending machine

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

On 04/04/2021 18:20, Ben Blaukopf wrote:
On Sunday, 4 April 2021 at 15:34:12 UTC+1, Brian Gaff (Sofa) wrote:
Are you worried about the insides of corners etc? How is it assembled at
corners, surely not like a water pipe with fittings? I don't think I've ever

It's been used like the plastic oval stuff - straight runs in plaster. No corners.

Experimentation in the garage says 2x1.5mm T+E just about fits, and a single three core is easy - provided that the cut end is reamed out properly.


That sounds about right as 2 x 2.5mm T&E just fits down 20mm conduit.

I would be temped to silicon both ends up after installing the cable.

I would also megger all cores against the copper after each pull before
connecting them up to anything else.

So are you going for a junction box setup or looping at the light fittings?


--
Adam

On Monday, 5 April 2021 at 10:57:51 UTC+1, ARW wrote:
On 04/04/2021 18:20, Ben Blaukopf wrote:
On Sunday, 4 April 2021 at 15:34:12 UTC+1, Brian Gaff (Sofa) wrote:
Are you worried about the insides of corners etc? How is it assembled at
corners, surely not like a water pipe with fittings? I don't think I've ever

It's been used like the plastic oval stuff - straight runs in plaster. No corners.

Experimentation in the garage says 2x1.5mm T+E just about fits, and a single three core is easy - provided that the cut end is reamed out properly..

That sounds about right as 2 x 2.5mm T&E just fits down 20mm conduit.

I would be temped to silicon both ends up after installing the cable.

to avoid chafing at the ends?


I would also megger all cores against the copper after each pull before
connecting them up to anything else.

Good plan.

So are you going for a junction box setup or looping at the light fittings?

Unless I want to chase out some more - and I really don't if I don't have to (and SWMBO *really* doesn't)- then aren't I tied to JBs (maintenance free, obvs)? For the first floor lights I'll try to put them outside the floor area of the planned loft conversion. Ground floor is less critical, because it's not affected by the planned works.

On 04/04/2021 14:20, Tricky Dicky wrote:




If you have loft insulation and the cables will run either across or through it you may have to uprate the cable to 1.5mm2 which make for a tighter fit.


Maybe not now we have LED lighting.

http://wiki.diyfaq.org.uk/index.php/Cables#Cable_Sizes

1.0mm T&E has a CCC of 16A so if we have to derate this by 50% it can
still be covered with a 6A MCB. Further say we then had to apply another
0.7 derating due to it been say 50deg then you still have 5.6A to play
with. That is 1.29kW. Now only if the OP has a load somewhere in that
region do you need to consider upping the cable size.

It matters not that in this case we are running the cable at a CCC
rating below the MCBs rating as the known load "should" be a lot lower.

If the OPs load is in that range then he would probably have to swap to
1.5mmm for voltage drop.



--
Adam

On 05/04/2021 11:15, Ben Blaukopf wrote:
On Monday, 5 April 2021 at 10:57:51 UTC+1, ARW wrote:
On 04/04/2021 18:20, Ben Blaukopf wrote:
On Sunday, 4 April 2021 at 15:34:12 UTC+1, Brian Gaff (Sofa) wrote:
Are you worried about the insides of corners etc? How is it assembled at
corners, surely not like a water pipe with fittings? I don't think I've ever

It's been used like the plastic oval stuff - straight runs in plaster. No corners.

Experimentation in the garage says 2x1.5mm T+E just about fits, and a single three core is easy - provided that the cut end is reamed out properly.

That sounds about right as 2 x 2.5mm T&E just fits down 20mm conduit.

I would be temped to silicon both ends up after installing the cable.

to avoid chafing at the ends?


Yes. Any movement over the years could be a problem.


I would also megger all cores against the copper after each pull before
connecting them up to anything else.

Good plan.

So are you going for a junction box setup or looping at the light fittings?

Unless I want to chase out some more - and I really don't if I don't have to (and SWMBO *really* doesn't)- then aren't I tied to JBs (maintenance free, obvs)? For the first floor lights I'll try to put them outside the floor area of the planned loft conversion. Ground floor is less critical, because it's not affected by the planned works.

I have always wanted to try one of these.







--
Adam

On Monday, 5 April 2021 at 11:27:36 UTC+1, ARW wrote:
On 04/04/2021 14:20, Tricky Dicky wrote:




If you have loft insulation and the cables will run either across or through it you may have to uprate the cable to 1.5mm2 which make for a tighter fit.

Maybe not now we have LED lighting.

http://wiki.diyfaq.org.uk/index.php/Cables#Cable_Sizes

1.0mm T&E has a CCC of 16A so if we have to derate this by 50% it can
still be covered with a 6A MCB. Further say we then had to apply another
0.7 derating due to it been say 50deg then you still have 5.6A to play
with. That is 1.29kW. Now only if the OP has a load somewhere in that
region do you need to consider upping the cable size.

50 degrees sounds a bit high?

In practice the first floor lights will be less than 200W.

Length of run is no problem. So 1.0 is looking attractive.

On 5 Apr 2021 at 10:57:47 BST, "ARW" wrote:

On 04/04/2021 18:20, Ben Blaukopf wrote:
On Sunday, 4 April 2021 at 15:34:12 UTC+1, Brian Gaff (Sofa) wrote:
Are you worried about the insides of corners etc? How is it assembled at
corners, surely not like a water pipe with fittings? I don't think I've ever

It's been used like the plastic oval stuff - straight runs in plaster. No
corners.

Experimentation in the garage says 2x1.5mm T+E just about fits, and a
single three core is easy - provided that the cut end is reamed out
properly.


That sounds about right as 2 x 2.5mm T&E just fits down 20mm conduit.

I would be temped to silicon both ends up after installing the cable.

I turned some little hardwood lipped washers for the ends of my 15mm copper,
but then they are on display as part of light fittings.



I would also megger all cores against the copper after each pull before
connecting them up to anything else.

So are you going for a junction box setup or looping at the light fittings?


--
Roger Hayter

On 05/04/2021 11:46, ARW wrote:
On 05/04/2021 11:15, Ben Blaukopf wrote:
On Monday, 5 April 2021 at 10:57:51 UTC+1, ARW wrote:
On 04/04/2021 18:20, Ben Blaukopf wrote:
On Sunday, 4 April 2021 at 15:34:12 UTC+1, Brian Gaff (Sofa) wrote:
Are you worried about the insides of corners etc? How is it
assembled at
corners, surely not like a water pipe with fittings? I don't think
I've ever

It's been used like the plastic oval stuff - straight runs in
plaster. No corners.

Experimentation in the garage says 2x1.5mm T+E just about fits, and
a single three core is easy - provided that the cut end is reamed
out properly.

That sounds about right as 2 x 2.5mm T&E just fits down 20mm conduit.

I would be temped to silicon both ends up after installing the cable.

to avoid chafing at the ends?


Yes. Any movement over the years could be a problem.


I would also megger all cores against the copper after each pull before
connecting them up to anything else.

Good plan.

So are you going for a junction box setup or looping at the light
fittings?

Unless I want to chase out some more - and I really don't if I don't
have to (and SWMBO *really* doesn't)- then aren't I tied to JBs
(maintenance free, obvs)? For the first floor lightsÂ* I'll try to put
them outside the floor area of the planned loft conversion. Ground
floor is less critical, because it's not affected by the planned works.

I have always wanted to try one of these.




These


https://www.screwfix.com/p/surewire-...ox-white/2742j

--
Adam

On Monday, 5 April 2021 at 13:25:31 UTC+1, ARW wrote:
On 05/04/2021 11:46, ARW wrote:
I have always wanted to try one of these.

These


https://www.screwfix.com/p/surewire-...ox-white/2742j

They do look nice. I was planning on using Ashley boxes, but at £5 per light/switch connection, the SureWire stuff will work out cheaper. I'll lose some on longer runs - but I need those anyway because I want all the JBs to be accessible from the eaves storage areas. I'll give them a go.

Finally got around to putting a Building Notice for the full rewire. Was supposed to start last year but work got in the way.

--
Adam

On Sunday, 4 April 2021 at 12:00:47 UTC+1, Ben Blaukopf wrote:
Finally got round to looking at the upstairs lights in this place, and discovered that all the chased-in cable uses 15mm copper as conduit containing 1 or 2 1.5mm cables (well, could be 1.0)


Pulled up some floorboards today (and split one of them ), and in the course of putting a temporary run in, discovered the existing wiring is stranded. Discovered some tags for 3/029 under the floor. This is quite fun. So presumably it was rewired in T+E in (presumably) the early 70s - at which point they appear to have surface mounted all the cables they couldn't hide in the original copper "conduit". Also found some of the original VIR in a copper pipe (I say copper. It looks like copper. Was 1/2" copper common in 1935??).

Also some twin-core (not in service, so far as I've been able to determine) and an obviously retrofitted 6mm (maybe) earth which I'm a bit worried about since it's still connected to the CU, and heading off in the direction of the bathroom. Surely someone hasn't connected the supplementary bonding back to the CU.... Or perhaps it's a main bond for the cast iron waste?

The wiring is still in good nick - but we plan on being in this house for a good while, so we'll gut the lot and then get on with decorating. If I can get hold of the guy inspecting it, I'll ask how he feels about calling the copper tube "capping" - otherwise I've decided to just rip it out and pick a different battle.

Wiring the lot in 1.0mm since loads won't approach anywhere near 6A. Planning to run a neutral to all the switches while I'm there.

The downstairs will be the fun bit. I want to insulate underfloor, I so I need to lift every floorboard. Not to mention 20sqm of laminate.