Two quickies...

1. I am shortly to rewire my upstairs lighting, (the wiring is in the
loft). When new loft insulation is shortly added the cable will be
buried under the insulation, but I am not clear whether the regs
require that the cable needs fixing to the joists, or can just be laid
loose along the ceiling, (as the current wiring is).
[NB. We have already discussed the cable derating implications in
another thread].

2. In replacing the wiring to the light switches, I intend to use the
existing cable to pull through the new stuff, (it is in oval conduit).
Has anyone got any tips for how to mechanically connect the two
cables, obviously with the smallest possible cross section to enable
the joint to pass through the conduit. Is insulating tape generally
strong enough ??

Mike Hall wrote on 11/01/2004 :-
2. In replacing the wiring to the light switches, I intend to use the
existing cable to pull through the new stuff, (it is in oval conduit).
Has anyone got any tips for how to mechanically connect the two
cables, obviously with the smallest possible cross section to enable
the joint to pass through the conduit. Is insulating tape generally
strong enough ??

The usual way would be to strip several inches of the copper bare to
allow a loop to be formed in the copper in each of the wires to be
joined. That keeps the bulk down and is sometimes covered with a layer
of tape. Much depends on how much room is to spare in the conduit and
how freely the cable moves inside it.

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"Harry Bloomfield" wrote in message
. uk...
Mike Hall wrote on 11/01/2004 :-
2. In replacing the wiring to the light switches, I intend to use the
existing cable to pull through the new stuff, (it is in oval conduit).
Has anyone got any tips for how to mechanically connect the two
cables, obviously with the smallest possible cross section to enable
the joint to pass through the conduit. Is insulating tape generally
strong enough ??

The usual way would be to strip several inches of the copper bare to
allow a loop to be formed in the copper in each of the wires to be
joined. That keeps the bulk down and is sometimes covered with a layer
of tape. Much depends on how much room is to spare in the conduit and
how freely the cable moves inside it.

And a little tape over the joint will put a taper over the new cable to
prevent snagging.

You need two people to do the pulling successfully. One has to keep the new
cable flat and prevent it snagging on the metal conduit as the other pulls
the cable through. Quite often the conduit is often sufficient to just push
a new cable through should you find a joint fails as you are pulling.

--
Adam

On 11 Jan 2004 02:01:55 -0800,
(Mike Hall) wrote:

2. In replacing the wiring to the light switches, I intend to use the
existing cable to pull through the new stuff, (it is in oval conduit).
Has anyone got any tips for how to mechanically connect the two
cables, obviously with the smallest possible cross section to enable
the joint to pass through the conduit. Is insulating tape generally
strong enough ??

If space in the conduit is limited (as it is bound to be) one option
would be to pull thru a length of curtain wire, and also a piece of
string (so that you've got the string and curtain wire in the
conduit), or perhaps pull the old cable out and pull some string thru
first, then pull thru the curtain wire AND further string.

Then you can put a hook in the end of the curtain wire to attach to
the new cable, and start pulling - without using the string.

The purpose of the string is that if the curtain wire becomes detached
from the new cable you can pull the curtain wire thru again on the
string.

Once you've got the new cable thru pull the string out because it
isn't needed any longer.

Make sure you use string which is strong though - none of this stuff
that spiders would reject for building their webs - if you can break
it by pulling between your hands it isn't strong enough.

You would also be well advised to dust the new cable with talcum
powder as it enters the conduit - this will greatly assist its passage
thru the conduit. However on completion it would probably be a good
idea to put the vacuum cleaner on the end of the conduit and give it a
good blow/suck to remove the "loose" talc - though it isn't likely to
be a big problem fine dust can be a fire hazard.

PoP

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On Sun, 11 Jan 2004 11:31:37 +0000, PoP wrote:

You would also be well advised to dust the new cable with talcum
powder as it enters the conduit - this will greatly assist its passage
thru the conduit.

As will pushing *and* pulling the cable simultaneously. Two people
needed...

Thomas Prufer

In article ,
Mike Hall wrote:
Has anyone got any tips for how to mechanically connect the two
cables, obviously with the smallest possible cross section to enable
the joint to pass through the conduit. Is insulating tape generally
strong enough ??

Strip back the outer sheath about 6 inches or so and cut off the earth.
Bare about 3 inches of the conductors. Form a loop by wrapping the bare
conductor over the insulation *in opposite directions* then do the same
with the new wire but of course thread one of the conductors through the
loop on the other first. Now pull tight and crunch the whole lot up as
smooth as possible with pliers, and cover with PVC tape. This will make a
mechanical joint nearly as strong as the cable itself - I've never had one
pull apart.

--
*Women like silent men; they think they're listening.

Dave Plowman London SW 12
RIP Acorn

"PoP" wrote in message
...

You would also be well advised to dust the new cable with talcum
powder as it enters the conduit - this will greatly assist its passage
thru the conduit.

Or some sort of grease: silicone, vaseline, KY jelly, butter etc

(When following up please remember it's before the watershed :-)



--
John Stumbles
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-+
If a job's worth doing, it'll still be worth doing tomorrow.

Mike Hall wrote:


2. In replacing the wiring to the light switches, I intend to use the
existing cable to pull through the new stuff, (it is in oval conduit).
Has anyone got any tips for how to mechanically connect the two
cables, obviously with the smallest possible cross section to enable
the joint to pass through the conduit. Is insulating tape generally
strong enough ??


What I do is as follows.

Strip off insulation outer on both.

Cut back all except one condictor and strip that.

fold over that and teh similar one on teh new wire, to make 'U's

Interlock those and twist together hard.

Cover the while joint in insulation tape.

This is about as small as it gets.

Some people use the old to draw a doubled string through, cut that, and
use one half to attach to the new wire., and leave the other in place
'just in case'

"The Natural Philosopher" wrote in message
...
Mike Hall wrote:


2. In replacing the wiring to the light switches, I intend to use
the
existing cable to pull through the new stuff, (it is in oval
conduit).
Has anyone got any tips for how to mechanically connect the two
cables, obviously with the smallest possible cross section to
enable
the joint to pass through the conduit. Is insulating tape
generally
strong enough ??


What I do is as follows.

Strip off insulation outer on both.

Cut back all except one condictor and strip that.

fold over that and teh similar one on teh new wire, to make 'U's

Interlock those and twist together hard.

Cover the while joint in insulation tape.

This is about as small as it gets.


And if the conduit, or hole is badly restricted, solder the twisted
ends, not much chance of that coming undone.

Gavin Gillespie wrote:

"The Natural Philosopher" wrote in message
...

Mike Hall wrote:



2. In replacing the wiring to the light switches, I intend to use

the

existing cable to pull through the new stuff, (it is in oval

conduit).

Has anyone got any tips for how to mechanically connect the two
cables, obviously with the smallest possible cross section to

enable

the joint to pass through the conduit. Is insulating tape

generally

strong enough ??


What I do is as follows.

Strip off insulation outer on both.

Cut back all except one condictor and strip that.

fold over that and teh similar one on teh new wire, to make 'U's

Interlock those and twist together hard.

Cover the while joint in insulation tape.

This is about as small as it gets.



And if the conduit, or hole is badly restricted, solder the twisted
ends, not much chance of that coming undone.



Not neeeded. I have tested a twisted joint to destruction. The cable
failed elsewhere :-)

Or some sort of grease: silicone, vaseline, KY jelly, butter etc

the screwfix silicone spray for gutters and plumbing is good on all sorts of
plastic including pvc

In article ,
Gavin Gillespie wrote:
And if the conduit, or hole is badly restricted, solder the twisted
ends, not much chance of that coming undone.

Soldering weakens the copper due to heat. A properly made twisted joint
won't come undone before the cable breaks. I've used 'my' method hundreds
of times - it was taught to me by an old sparks.

--
*A nest isn't empty until all their stuff is out of the attic

Dave Plowman London SW 12
RIP Acorn

Form a loop by wrapping the bare
conductor over the insulation *in opposite directions*

Do you mean wrap the red core over its insulation then the black core over
its insulation?

Mike Hall wrote:
snip
2. In replacing the wiring to the light switches, I intend to use the
existing cable to pull through the new stuff, (it is in oval conduit).
Has anyone got any tips for how to mechanically connect the two
cables, obviously with the smallest possible cross section to enable
the joint to pass through the conduit. Is insulating tape generally
strong enough ??


Recently had the whole house rewired and the sparks semed to loop
and twist one end of the conductors of one wire.
, thread all the conductors of the other wire through the initial loops
twist the individual loops together, then cover the lot in insulating tape
they didn't use talc., baby oil or other lubricants.

Pic just in case my description is a bit garbled
http://www.cheesesoup.pwp.blueyonder.co.uk/images/w.jpg


--
Yours S. addy not usable (not that you would try it) ( )
Utinam logica falsa tuam philosophiam totam suffodiant! / \
www.killies.co.uk/forums/index.php

In article ,
Pablo wrote:
Form a loop by wrapping the bare
conductor over the insulation *in opposite directions*

Do you mean wrap the red core over its insulation then the black core
over its insulation?

No - red over black and the reverse. You're forming a 'woven' loop.

--
*I yell because I care

Dave Plowman London SW 12
RIP Acorn

Thanks to everyone for some top tips - how about the clipping cable in
the loft question.

"Mike Hall" wrote in message
om...
Thanks to everyone for some top tips - how about the clipping cable in
the loft question.

Don't clip it where it will be stood on or something laid on top of it. Try
to keep cable runs around the edges if you plan not to drill through joists
and other timbers. If you do have to cross over a joist where you plan to
store items, then give the cable some robust protection so it doesn't get
squashed. That's about it.


---
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Mike Hall wrote:
1. I am shortly to rewire my upstairs lighting, (the wiring is in the
loft). When new loft insulation is shortly added the cable will be
buried under the insulation, but I am not clear whether the regs
require that the cable needs fixing to the joists, or can just be laid
loose along the ceiling, (as the current wiring is).
[NB. We have already discussed the cable derating implications in
another thread].

Don't clip wiring if it can be avoided! Just lay it with enough
slack, it's better to run it through then over the insulation.


2. In replacing the wiring to the light switches, I intend to use the
existing cable to pull through the new stuff, (it is in oval conduit).
Has anyone got any tips for how to mechanically connect the two
cables, obviously with the smallest possible cross section to enable
the joint to pass through the conduit. Is insulating tape generally
strong enough ??

As said before, hook the wires together then twist (so they're
joined by "eyes") - additionally, I have found fewer problems
when pulling wiring *up* conduits, rather than down. If you have
the misfortune to have a cable joint break so you have nothing
left to pull through with, you can suck a piece of strong string
through the conduit with a vacuum cleaner nozzle.


J.B.