Why aren't ring circuits banned?

[chronyx]

Doing a lot of EICRs in London at the moment and I'd say every other C.U. has a ring circuit with no continuity on one of the conductors.

Seeing as the IET see fit to tinker around the edges constantly with the regs, I struggle to understand why these potentially extremely dangerous circuits are still permitted. Yet bonding and earth conductors have almost doubled in size because, well, they said so.

It's not 1949 anymore. Ban the damn things.

 

[Andy78]

Yes you are correct, with the early pvc cable, nothing wrong with it other than quite messy, just wipe it off. green gooey mess.

When I have encountered the goo before, the insulation has been wrecked.

 

[7029 dave]

When I have encountered the goo before, the insulation has been wrecked.

I have never experienced this Andy. Learning all the time.

 

[Andy78]

I have never experienced this Andy. Learning all the time.

One example was a house with estimated 40+ year old twin pvc cable. Only one circuit had evidence of goo, the downstairs lighting, but it was evident at all points on the circuit. All circuits displayed degraded insulation values, but this circuit was by far the worst.
It had been running at around 6-7A for decades due to chandeliers full of 60W lamps. My theory is that the heat involved in the load combined with the already degraded insulation helped to displace the plasticiser which added to the cable degradation, and so on and so on.
No goo was present in any of the other circuits of the same age, but these had probably not seen a sustained load as high in relation to their CCC.

Only a theory mind you and I would wecome education from others experiences.

 

[kingeri]

This is exactly what my house was like when I moved in, the lighting circuit had the green goo but the other circuits didn't, and I believe they were all of the same age.

 

[westward10]

The green goo is a component of the insulation and should not give poor IR readings.

 

[Andy78]

The green goo is a component of the insulation and should not give poor IR readings.

If the goo is a component of the insulation, and it's running out of the ends of the cable, is this not indicative of a breakdown of the insulation ?
In my example there were poor IR readings on all circuits mind you, but the worst featured on the gooey circuit. The insulation was also physically degraded on this circuit, being brittle and cracking at the stripped ends.This could have been just due to current related heating, but I feel that lack of a plasticising agent cannot have helped.

 

[Midwest]

The video Dave posted does describe the fault, if you have a watch. I've come across it numerous times and I advise my client and referenced this pdf file;
http://www.napitonline.com/downloads/CP 6 07 P 28 Ask Eddie Green Slime.pdf
Quoting from it;
'The green slime is Di-isoctyl Phthalate. It is a bi-product of a reaction between the plasticiser in the insulation and the copper conductor. This plasticiser had an anti-oxidant added to it between 1965 and 1971 – and so is not so common, although these symptoms could have become more noticeable following the installation of a central heating system, for example, as it is thought that high ambient temperatures accelerate the process'.

In the situations I've encountered, mostly minor works, the IR readings have been acceptable but lower than other similar installations not affected by slime. In these instances, my client's have chosen not to replace cabling. However on one job, the green slime was quite bad at the light switches and in numerous JB's under the floor. In this instance, my client decided to rewire. But his decision was influenced by the poor general state or the wiring, diy additions made and the fact that he was renovating the property.

This fault will affect the flexibility of the cables, so will not present an issue, until cables are moved. Most likely, when the client has swanky new metal pate fittings installed!

Personally, if I found this in a property I had bought, I would rewire regardless of any test results. We are talking of cabling over 45 years old, and at some point would require rewiring in any case.

 

[David Prosser]

I have just googled it, and they do say it came out after the war, Rubbish all the rewires I have done in that era, it is all radials, the RFC took off big time in the early 60's.

Hi my house (built 1960) had a one RFC for all sockets in rubber insulated. Most of the insulation crumbled as I removed the cables. I will have look through later for some pictures but I think I only took a few of the lighting circuit as the rubber had melted in thatone.

 

[mydigitalhome]

All types of circuit have their place !
Generally find people who like radials test with a plug in socket only and hope all the sockets work.. Saves time having to do continuity test and limit everything else out. Tick for continuity only with no values. Fell about laughing first time I saw it on a test sheet. Often happens in Europe as often don't need need to be a sparks to sign off tickets just need to have a degree in any subject. Madness but still don't seam to have loads of deaths from it.