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Discuss Green slime from old cables in the Electrical Forum area at ElectriciansForums.net

Doomed

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Arms
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Is there a conclusive article or risk assessment about green slime (from those old late 1960's cables).
The only things that seem to agree are that it is mildly toxic and it does not reduce the insulation resistance.
Napit say does not need a rewire
several cable manufacturers say it ought to be replaced
SEC says it must be rewired
So does anyone have anything conclusive?
 
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Andy78

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Arms
Esteemed
It is toxic and can cause skin irritation.
It is a sign of the cable plasticiser breaking down.
It is usually associated with low IR results in my experience.
It needs rewiring if the IR results indicate a problem.
It can be left in if all tests come back to indicate a healthy circuit.
 
If the cables test as healthy they can be left. But I would notify the customer of findings, what is happening and give them the option of renewing. If they don’t at least they are aware of the matter and know that it may well be needing replacing in the future.
 

Sintra

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Deleted member 26818

This scenario is one where it’s up to the inspector to make a judgement call.
If all the readings are good, and the fabric of the installation is sound.
I wouldn’t advise a rewire.
I would probably advise a shorter time for future inspections, 5 years instead of 10.
If readings are down, but still acceptable, I may advise future inspection every 2 or 3 years.
If readings are very poor, then yes, I would advise a rewire.
 

Midwest

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Arms
Esteemed
I've come across it on a couple of occasions. One replacing damaged socket outlet, informed the client, gave them this leaflet from Napit;

Never heard a thing

Another occasion, client had just bought the house, and was extensively refurbishing. They decided to rewire.

Thing is, the stuff comes from the 60's-70's, most manufacturers give their cables a 20 year life span. If you've got 60's wiring and spending dosh on your house, its a no brainer to rewire. Its probably been attacked by DIY'ers in those 60 years.
 
As above John Ward gave similar advice in a video, cables are 40 plus years old but like Spin London has said if it tests okay no need to replace. Judgement call, advise on age then it's up to client.
 

Doomed

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Arms
  • Thread Starter Thread Starter
  • #10
Do you have a link I could forward to that draft statement?
I have links to the napit advice and the cable manufacturers advice, this one you quoted would be another good evidence to put into a compilation and pass on to the estate agent that called me in to look at a green socket.

I want to present independant information rather then my own viewpoint (so they can make their own conclusions rather then hold us liable for any final decisions on wether to rewire or leave it alone)
 
I want to present independant information rather then my own viewpoint (so they can make their own conclusions rather then hold us liable for any final decisions on wether to rewire or leave it alone)
I suspect that the reason you have been asked to carry out an assessment, and, I presume, get paid for it, is that you are competent in this area. I think they will expect you to test, inspect and consider the situation before giving a clear answer. If they were happy to come to their own conclusion then they would have just googled it.

Step up. Write a report. Show all the variables and relevant information, then make a decision based on the facts. Then submit the invoice happy in the knowledge that you did a good job.

Oh, and make sure your insurance is up to date.
 

Lucien Nunes

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Arms
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Another argument in favour of rewiring is that loss of plasticiser can physically weaken the insulation even while its insulating properties are still OK. I have never had to advise a rewire specifically because of green goo, but I have recommended shorter inspection intervals and customers have opted for a rewire because of that.
 
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