In article ,
Scott wrote:
On Wed, 16 Aug 2017 23:41:20 +0100, "Dave Plowman (News)"
wrote:

In article ,
Scott wrote:
On Wed, 16 Aug 2017 00:20:20 +0100, Michael Chare
wrote:

On 14/08/2017 22:35, Scott wrote:
Does anyone know if you can still buy cable by the metre at B&Q or do
you have to buy a whole reel?


For a DIY extension lead, I did find that PVC cable was easier to find
and cheaper than rubber.

I wouldn't use rubber. It tends to perish after a few years and
become brittle.

Odd then that most high quality power tools have rubber, rather than PVC,
flex?

Not comparing like with like. Flex has to be able to be twisted,
coiled or whatever hundreds of times (clue lies in the name) and is
not generally expected to last 40 years. Nobody would wire a house
using flex.

May be out of date but:

"Part P approved document Appendix C

"Tough Rubber Sheathed (TRS), vulcanized rubber insulated (VRI) cables

"Prior to the use of pvc insulated cables becoming common in the
1960s, most cables installed in domestic dwellings were of the rubber
insulated, tough-rubber sheathed (TRS) type. These are easily
recognizable by their black exterior.

"The extent to which the insulation and sheath deteriorate in service
depends very much on whether the cable has been subjected to
overloading and/or excessive temperature, or the rubber has been
exposed to direct sunlight. Deterioration results in a loss of
insulating properties, with the rubber becoming dry and inflexible,
perhaps with a tendency to crumble.

"Such wiring installations should be tested by a competent person at
the earliest opportunity, but otherwise left undisturbed until
replacement, as they are beyond their normally expected safe working
life."

This does not look like encouragement to use rubber cable to me.

You are confusing two different applications; Permanent wiring and flexible
cables. For flexible cables, which can usually be replaced fairly easily,
rubber has the advantage of being much more flexible than PVC and doesn't
stiffen due to low temperatures.

--
from KT24 in Surrey, England