Conor,

  Phenolic mouldings on GPO telephones of 1929 vintage  tend to crack and not to like sunlight

on them. This is the first sign of decomposition.. They will not last forever.

What are the indications of cut out failure?

Is decomposition of cables causing deposits that start tracking?

Damp environment will cause phenolic stuff to fail. Damp will also cause tracking obviously.

My cut out is possibly 50 years old, dry and ok so far.

Terence.

I assume we are alluding to this.

The MOCOPA guidance says to test for a surface voltage that does not disappear when a current is drawn (so not be fooled by high impedance DMMs), and only in that unlikely event to treat it as dangerous. The warning suggets the risky ones were installed between 1967 and 1992

Given the no of pre- war asbestos insulated unearthed metal cased ones in use, I suspect we should do those before we worry about the modern ones.  I do not think this problem is common.

Mike.

The black cut-outs I've come across that went pop were generally "overloaded" (apparently their stated 100A rating was only for intermittent loads, they're only good for 60A continuous) - and  mostly ended up with the DNO's fuse blowing. I'm not sure if that was due to localized overheating in addition to the loads, or the plastic between live conductors breaking down to cause a short, but there does seem to be a tendency for them to self-disconnect as it were, if not entirely removing the danger at least making the problem obvious and causing the DNO to be called out post haste.

   - Andy.

Unknown said:

Should we replacing them, or waiting until they deteriorate?

Who is "we"?

AFAIK, there is not only no programme of routine replacement, there is no programme of inspection. At least in the days when the electricity boards sent somebody round to read the meter, there was a chance that any deterioration might be spotted and reported.

Given that the document @mapj1 referenced was published in January 2018, how come as a working electrician who probably worked around possibly over eight hundred such cut outs, this is the first time I have heard of these issues?

There’s eighteen references to surface voltage on plastic and phenolic cut outs in this SPE Energy Netdocument.

www.spenergynetworks.co.uk/.../OPSAF-12-021.pdf

So, another hazard in the cupboard under the stairs 

www.whatdotheyknow.com/.../Annex 1.7 MOCOPA Guide Version 3.5.pdf

Because there's less likely to be insulation there and moisture may get in and affect the cutouts?

It is good to be aware of it, but to calibrate if action is really needed or not. we also need to be aware how common this is as well - my earlier remark about cast  iron and asbestos is not totally flippant - there are a great many things that could be a risk -  but we need to focus the time and money on the ones seen frequently in the wild - as the ones most worth worrying about.

So if we could find out how many times the 'A19' call has been made by meter 'operatives' compared to say smashed fuse covers, or evidence of overheating which also have their own, different 'A ' codes that would be germane. There may well be a problem with the state of company cut-outs generally, after all in the modern privatized world no-one is really looking at them, but it would be good to know the 'top ten' most common dangerous things to look for - avoids focusing on what may be a distraction.

Mike.

This is an incomer in Cardiff,  I think the cable and pitch filled spreader were installed in the late 1800's, in the one document above it says this is safe to work on without isolation as the DNO equipment are separate components. 

I have had customers whose front gardens were dug up and the original supply cable cut to isolate the DNO equipment to replace it along with the meter with a new supply cable run in from where the original was cut.

Plastic equipment does get condemned.