"Electrical cables have a life, 15 to 20 years."

[itselectric]

Way back in the sixties we were never told to keep circuit runs separate, so we drilled holes in joists and ran cables from separate circuits through the same hoLe and got as many as we could through each hole. then when the 15th came out it was part of the regs to keep circuits separate in their runs. I would say going on the fact that there are more electrical appliances and larger power rating that a lot of these cable would run a "bit " warm and have HOT spots where they passed through these joists so on that basis, a lot of dwellings wired in pvc would be better off being rewired.
This is of course more than the specified 30yrs

 

[davesparks]

What do you mean by keeping circuits Sepererate?

 

[HappyHippyDad]

I'd say visual inspection especially at the accessories is equally important as testing but if insulation integrity is good then time is but an abstract.

Love it Marvo. You bring a deep philosophical discussion about the abstract nature of time and relate it to IR

Shouldn't be too hard, the whole place is wired in copper conduits with sweated brass fittings as far as I know so it should be a case of just pulling in some new singles

Equally love it! Perhaps a days work Dave ;-)

 

[uksparks]

A load of shrite.

i often get asked to rewire a house etc... I say why? Who said so...

I tell them, jus because it's old doesn't mean it needs replacing. So long as it tests out ok, what's the problem.

i changed a board today as it happens, I'd say the wiring was probably 1975 - 1980, tested out beautifully. Actually it may have been older than than as it was all solid green sleeving.

 

[davesparks]

A load of shrite.

i often get asked to rewire a house etc... I say why? Who said so...

I tell them, jus because it's old doesn't mean it needs replacing. So long as it tests out ok, what's the problem.

i changed a board today as it happens, I'd say the wiring was probably 1975 - 1980, tested out beautifully. Actually it may have been older than than as it was all solid green sleeving.

Inspection and test, not just testing. Some absolute horrors can test out fine but not pass inspection.

 

[HappyHippyDad]

I'd say visual inspection especially at the accessories is equally important as testing but if insulation integrity is good then time is but an abstract.

I expect its just as Lucien has said. If this is a press article then the chap probably said something along the lines 'cable has a rating of 20 years'. I doubt the word 'rewire' ever came up until the journalist decided to embellish.

 

[PEG]

Inspection and test, not just testing. Some absolute horrors can test out fine but not pass inspection.

Spot-on...i was reminded of one,on reading this^ A radial in VR,to a water heater cupboard,where ALL the insulation had crumbled off,on an 8" section below.

A combination of age,temperature and stacked towels,rubbing away...

IR readings were excellent.

As with most things,a combination of factors,affect the outcomes of test/inspection,as they duly affect the safe working life,of any given cable.

 

[Risteard]

Inspection and test, not just testing. Some absolute horrors can test out fine but not pass inspection.

Indeed, and remembering that inspection is actually the more important part of the process! Testing merely supplements the inspection.

 

[itselectric]

What do you mean by keeping circuits Sepererate?

I mean physically not electrically, running cables in close proximity to each other causing overheating, when the circuits are in use.

 

[davesparks]

I mean physically not electrically, running cables in close proximity to each other causing overheating, when the circuits are in use.

Yes, which is what grouping factors are applied for. But you mentioned running T&E through joists domestically where it wouldn't apply due to the nature of the usage of the circuits

 

[GEOFF S]

With regards to some cables he is right, some PVC cable is only expected to last 20 years, others up to 50 years, the way PVC degrades is a difficult one, you may test and everything is fine, 5 years later not so due to degradation.

I think any house wired in the 60's to 80's need to consider a possible rewire especially if the house is to be renovated at considerable cost, these cables are 40 to 50 years old.

Also is the current installation really adequate for today's needs.

Read this BASEC

There are no requirements for life expectancy set out in cable standards and specifications. However, reputable cable manufacturers will state a probable life expectancy for their products, which for building wiring is usually 20 years when run at the rated temperature. However, under ideal circumstances, with lower loadings and minimal heating, it has been observed that cables can remain safely in operation for up to 50 years.
Cables degrade over time primarily due to changes in the polymers used for insulation and sheathing. The main cause of polymer degradation is too much heat, from either excessive current loading or from the environment - such as heated spaces. Cables loaded or heated for 24 hours a day will degrade faster than those used only during working hours – for example, commercial lighting circuits are often operated continuously.
If cables are overheated or overloaded it is possible to estimate reduced lifetimes. For example, regular PVC installation cables might last for 20 years if used at their rated temperature of 70ºC, but this would reduce to seven years at 80ºC and a matter of months if operated above 100ºC.
The conductors of a cable will normally maintain their performance indefinitely, but if accessories are changed frequently, crushing damage may occur to the exposed ends. Corrosion can sometimes occur with aluminium conductors and rusting can also affect the conductivity of steel armour.
Cables mounted or used outdoors are prone to very rapid degradation by UV exposure, so it is important that a type recommended for outdoor use is employed.
When deciding whether cable should be replaced during a refurbishment, installers and end users should not just look at the cable as it is now, but consider the possibility of degradation and failure in the period before it is next likely to be assessed, which might be another 10 years. If a major refurbishment is underway it may be less disruptive to replace cables now, rather than take the risk.



Cheers

 

[Besoeker]

So everything built 20 years ago or more is in urgent need of rewiring??
Baw locks. IMHO.

 

[GEOFF S]

So everything built 20 years ago or more is in urgent need of rewiring??
Baw locks. IMHO.

Read the full article.

He does say the condition of the cables are unknown, so 20 years is what the industry state as an expected life span, testing and inspection would be required to tell you if its urgent, i suspect he has no knowledge of the condition, so hes made a speculative comment , is he really going to say anything different than what the cable manufacturers and associates recommend?

Cheers

 

[Besoeker]

Read the full article.

I did.
"Electrical cables have a life, 15 to 20 years." is an unqualified statement.
And I still think it's bawlocks.

 

[uksparks]

Inspection and test, not just testing. Some absolute horrors can test out fine but not pass inspection.

When I say tests out, I mean tests out fine and all visibly fine too. Obviously I am not going to go digging in walls and floorboards looking for problems, but so long as its all safe and sound its good to go.