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

Discuss "Electrical cables have a life, 15 to 20 years." in the Electricians' Talk area at ElectriciansForums.net

mattg4321

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Quote from the president of the chartered institution of building services engineers.

See below.

http://www.bbc.co.uk/news/uk-politics-35749075

Agree or disagree? Seems like a rather sweeping generalisation to me. I'd be interested to hear from those on here that might've had a role in maintaining historic buildings such as the Houses of Parliament. I refuse to believe they rip out cabling that is perfectly serviceable just because of an arbitrary time limit?!

I seem to remember learning about the lifespan of cables at college, quite a few years back now so I'm struggling to remember. 20 years does ring a bell - but I'm sure that was if it was run continuously at full operating current and temperature? Admittedly most of my work is small commercial/small industrial/domestic but I'm sure I've not come across many cables running at 70 degrees continuously.

So what do we think? I might be way wide of the mark but I would've put money on it that the HoP have some cables still in service that are a multiple of 3/4+ of 20 years in service. Is this guy just a massive jobsworth?!
 
When I had my last assessment (Stroma) the guy told me that if a house has cabling (so T&E) over 30 years old it needs ripping out and replacing, regardless. No IR tests, just replace. Bollox if you ask me. As far as I am aware 1) The actual copper never deteriorates, it is purely the insulation, 2) The condition of the insulation is totally dependant on the operating temperature over time and it can either be knackered or as good as new. The only way to tell is to test it?
 
mattg4321 said:
Quote from the president of the chartered institution of building services engineers.

See below.

http://www.bbc.co.uk/news/uk-politics-35749075

Agree or disagree? Seems like a rather sweeping generalisation to me. I'd be interested to hear from those on here that might've had a role in maintaining historic buildings such as the Houses of Parliament. I refuse to believe they rip out cabling that is perfectly serviceable just because of an arbitrary time limit?!

I seem to remember learning about the lifespan of cables at college, quite a few years back now so I'm struggling to remember. 20 years does ring a bell - but I'm sure that was if it was run continuously at full operating current and temperature? Admittedly most of my work is small commercial/small industrial/domestic but I'm sure I've not come across many cables running at 70 degrees continuously.

So what do we think? I might be way wide of the mark but I would've put money on it that the HoP have some cables still in service that are a multiple of 3/4+ of 20 years in service. Is this guy just a massive jobsworth?!
Click to expand...


Jobsworth and I was a civil servant so I know all about jobsworths
 
What a load of cobblers. As we all know, only testing can indicate the condition of a cable.

I have tested VIR at 60 plus years old that has been good for continued service. I would expect most domestic PVC cable to last a good 40 years. I believe manufacturers give a 25 year life expectancy on most cable.
The only really knackered cables I have seen have been VIR and some 40-50 year old PVC that had been running at or over it's CCC for decades.
 
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'd say this was utter nonsense, have seen and tested hundreds of old T&E cables, often imperial sizes and 40+ years old and generally they are absolutely fine. Of course it depends on the environment, T&E installed outdoors will become very brittle within maybe 10 years and obviously continuous overloading will cause problems but all installations are different.
 
sparksburnout said:
When I had my last assessment (Stroma) the guy told me that if a house has cabling (so T&E) over 30 years old it needs ripping out and replacing, regardless. No IR tests, just replace. Bollox if you ask me. As far as I am aware 1) The actual copper never deteriorates, it is purely the insulation, 2) The condition of the insulation is totally dependant on the operating temperature over time and it can either be knackered or as good as new. The only way to tell is to test it?
Click to expand...

I bet if the STROMA guy was told he needed to fork out a few grand to rewire his house which tested out perfectly fine he'd pretty soon change his tune. Always easy to spend other punters money.
 
Don't forget this is a news article, which means any technical content is likely to be 50% random nonsense and misquotes. Of course actual insulation life depends crucially on temperature, load and the exact composition of the batch of material it was made from. You could probably take a reasonably educated guess at the useful remaining lifespan of the installation with the aid of a few chemical analyses of typical cable runs and a survey of operating conditions. The problem with taking an educated guess in a high profile situation such as this is that no-one can afford to be wrong. The surveyor will err on the side of caution, and the people he reports to will shave a bit off that to cover their own backs, etc. etc. Before you know it nobody is prepared to vouch for it lasting more than a few years, even where it's in AOK condition now.
 
As I thought too.

It'd certainly be an interesting job rewiring the houses of parliament though, and a very big one needless to say! Not sure I fancy it though.
 
That is bit of an sweeping statement, load of rubbish, visual inspection and testing is the only way, environment , temperature, conditions will determine the life span of any cable.
 
mattg4321 said:
As I thought too.

It'd certainly be an interesting job rewiring the houses of parliament though, and a very big one needless to say! Not sure I fancy it though.
Click to expand...

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
 
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
 
Last edited by a moderator:
Marvo said:
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.
Click to expand...

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

davesparks said:
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
Click to expand...

Equally love it! Perhaps a days work Dave ;-)
 
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.
 
uksparks said:
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.
Click to expand...

Inspection and test, not just testing. Some absolute horrors can test out fine but not pass inspection.
 
Marvo said:
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.
Click to expand...

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.
 
davesparks said:
Inspection and test, not just testing. Some absolute horrors can test out fine but not pass inspection.
Click to expand...

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

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
 
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 said:
So everything built 20 years ago or more is in urgent need of rewiring??
Baw locks. IMHO.
Click to expand...

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
 
davesparks said:
Inspection and test, not just testing. Some absolute horrors can test out fine but not pass inspection.
Click to expand...

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.
 
Well, I'll tell you now, that the cables are the last things that need pulling out of there and chucking on the scrap heap. The shower of sh1te that has been masquerading as a government for the last 50 years and progressively sold off and fooked the country up need recycling, not the cables. Sorry, couldn't resist it.
 
Just before Christmas I returned to a house I had re wired back in 1970 I was just an apprentice at the time.
Daughter of the couple that had lived there all those years asked for it to be re wired once again, the couple had passed away a few years back.
I was 17 on the first re wire, 63 now. Talk about a trip down memory lane.
I remember on completion thinking to myself, I won't be doing the next one.
Unless Dewalt do zimmer frames lol.
 
He was speaking in context, that context being that manufacturers place a nominal lifespan on their products. What you read was one sentence.
 
He was speaking in context
Click to expand...

I think he was speaking out of context. The article was talking about a specific installation, and he gave what is perhaps a worst-case specification that rarely applies to installations of the type being discussed. Had he said: 'Cables can usually be counted on to last 20 years, sometimes they last much longer, but it all depends on their working conditions' the uncertainly would have been explained for the lay reader.
 
Is it just sparky's who bicker among'st themselves or do other trades do the same ??
I must admit I have been on sites where some sparks have had a very arrogant attitude full of self importance.
But I do explain to other tradesman a door knob is a knob regardless of profession. :lol::icon12:
 
baldsparkies said:
Is it just sparky's who bicker among'st themselves or do other trades do the same ??
I must admit I have been on sites where some sparks have had a very arrogant attitude full of self importance.
But I do explain to other tradesman a door knob is a knob regardless of profession. :lol::icon12:
Click to expand...

My mum thinks I am lovely.:35:
 

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