Old Rubber

[cbw]

Went out today to fit some lovely shiney new metal switch plates........

Not only no earth in lighting circuit but so past its sell by date it crumbled on movement.

How can this sort of thing not be picked up on survey or mentioned by previous sparks....recent kitchen refit.

The whole place is rubber and really had it, not seen one this bad for a while.

Danger notice issued.

When did they first start installing the rubber cables?

 

[malcolmsanford]

Went out today to fit some lovely shiney new metal switch plates........

Not only no earth in lighting circuit but so past its sell by date it crumbled on movement.

How can this sort of thing not be picked up on survey or mentioned by previous sparks....recent kitchen refit.

The whole place is rubber and really had it, not seen one this bad for a while.

Danger notice issued.

When did they first start installing the rubber cables?

Well think you answered yourself .......kitchen fit, kitchen fitter so only part scope

Well PVC Twin and Earth came in right at the start of the 60's but think VIR was still being used as new well into the 60's. I started '71 and no VIR was used then but must be minimum 40 yrs old an installation that as it.

 

[nickblake]

VIR was started to be phased out in the late 50's early but was still in use in the mid 60's if the insulation is crumbling there is no option but to rewire , goood to see you covered yourself with a danger notification ,so many people still have well it works ok attitude , its one of those you just have to advise and walk away , if its an elderly couple over 60's grants are available for this type of sinario

 

[nickblake]

Paper

• Paper insulation
• From the WW1 era
• Very rare now in domestic wiring
• Paper is somewhat hygroscopic
• Pre-war paper cable is still in service in distribution networks, and causes a good deal of downtime
• The polychlorinated bipehnyl (PCB) used in old paper insulation is toxic, and the insulation should not be handled with bare hands

Lead sheathed

• Common in 1930s for socket circuits
• Used as exterior farm cable well after that
• Lead sheath does not make reliable earth connections
• Rubber inner insulation
• Tail rubber insulation tends to disintegrate, and muck accumulates on cable ends causing leakage

VIR

• Vulcanised India Rubber insulated cable.
• Along with imperial T&E, one of the most common historic wiring cables still in use
• Comes in 2 forms:
  • Twisted pair, cotton/rubber insulated, with no outer sheath
  • singles drawn into conduit
• Most VIR wiring doesn't include an earth wire, which is sometimes run as a separate uninsulated single.
• Rated to 60C
• Rubber insulation perishes, cracks & falls off
• Properties with VIR cable are usually in urgent need of rewiring, and may represent a significant safety risk. However some of the Jute / Hessian reinforced rubber cables that are often seen on consumer unit incomers are still often relatively safe.

A good percentage of the remaining old VIR wiring is now in a dangerous condition, especially at termination points. It is common to see insulation that has fallen off, often leaving live & neutral conductors bare, unsupported and in very close proximity. In the worst cases 2 bare conductors can be found twisted round each other with nothing rigid to support them.
The outer insulation has failed on the black sheath of the cable, and in one place the insulation on the inner live wire has also cracked off. This cable is in a very poor state, and is unsafe.
The rule of thumb with old rubber wiring is

• replace it as soon as possible
• don't move it at all, even small movement sometimes causes shorts.

This situation is quite different to early American rubber wiring, which is usually still in sound condition, due to the use of a different rubber formulation.


TRS

• Tough Rubber Sheath
• Rubber insulated conductors with a rubber outer sheath

CTS

• Cab Tyre Sheathed
• Tinned copper conductors, each core insulated with VIR, & cab tyre outer sheath
• Single, Flat Twin and Flat Triple
• (I'm not familiar with this one, but presumably it looks like TRS)

Aluminium

• Cheaper alternative to copper
• Used from 1950s to 1970s, and old stock sometimes used into the 1980s.
• The insulation & sheathing is mostly the same as T&E - PVC for decades, may be rubber on older cable.
• A known fire risk
• Aluminium cable creeps, oxidises & fractures, all of which can cause fires.
• Requires special connections, do not connect to old ali cable using connectors intended for copper.
• Al requires a larger conductor size than Cu for the same current rating
• Presence of aluminium cable may be considered a material fact for insurance.
• The main problem with ali cable is its thermal expansion coefficient. Repeated temperature cycling causes it to come loose at connection points, and it then oxidises, and aluminium oxide is an insulator. Bad connections generate excessive heat and fire can break out.

Copper Clad Aluminium

• Each conductor has an aluminium core surrounded by copper
• An attempt to improve the properties of ali cable
• Significantly better than al, the surface oxidation problem is eliminated, creep reduced & the risk from cracking more or less eliminated

PBJ

• PolyButyl Jute insulated cable
• Rubberised Hessian appearance to the sheath.
• The surface is these cables is quite uneven
• Commonly used for mains incomer insulation
• Lots of old PBJ is still safely in service

Imperial T&E


PVC twin


Older T&E wiring having similar construction to today's cables. Several versions exist:

• 7/.029 T&E
  • imperial 7 stranded version of 2.5mm² T&E
  • used for socket circuits until unstranded 2.5mm T&E was introduced around 1970
  • strands are 0.029" diameter = 0.74mm
• 3/.029 T&E
  • imperial 3 stranded version of 1mm² T&E
  • used for lighting circuits
  • 1/.044" unstranded lighting cable also used
• Ashathene T&E
  • Precursor to PVC T&E
  • Lasts well
• PVC outer VIR inner
  • an early T&E cable
  • where the inner rubber has failed, the tails can be sleeved
• 2 core Twin
  • no earth, used for lighting circuits, or power circuits with a separate (usually uninsulated) single run alongside to provide an earth.

PVC and ashathene versions of this cable last well and are usually in good condition, but rubber does not last well long term.
PVC outer rubber inner cable can have its rubber ends sleeved to make it safe, as its only the ends where exposed to air where the rubber becomes brittle and falls off. Cable with rubber outer insulation can not be made safe this way.

 

[m4tty]

Think ^^^ that just about covers it lol nothing more to add

 

[ste mac]

What about this one!

http://www.electriciansforums.net/e...lectrical-regulations/15208-cable-system.html

 

[cbw]

Thankyou very much!

 

[nickblake]

i have come across it many years ago when i was a kid and i cant for the life of me remember what it was called but i will see if i can search it out

 

[jpmiff]

Hi nickblake,

very interesting post

 

[nickblake]

thank you , i have some more pics , some were taken at a periodic last year when i found a complete installation wired in VIR singles original wiring dating back to the 30's all still in use it was a shame it had to be taken out , ill try and find them and post the on here

 

[paulrayner]

Well think you answered yourself .......kitchen fit, kitchen fitter so only part scope

typical sparks all too ready to knock kitchen fitters. were not all bad you know. I get tired of listening to people bangin on about us. theres good and bad in all trades. Including sparks i,ve personally come across & put right bad jobs from a so called qualified sparks with there ficticious test results. i,m a full scope kitchen fitter by the way.

 

[nickblake]

blimey

 

[cbw]

Toys out...........

 

[Des 56]

"Old rubbber"

The title persuaded me that CBW had just lost his faithfull old horse

 

[paulrayner]

toys out...........

eye your probably right but it does get up my nose abit