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Topic Title: Meter tails in insulated wall cavity.
Topic Summary: Effect on service life?
Created On: 20 March 2013 09:48 AM
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 20 March 2013 09:48 AM
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Phased

Posts: 18
Joined: 10 September 2006

I recently carried out a EICR for a pensioner living in a mid 1970's constructed bungalow. When she and her husband moved in approx. 25 years ago they had the cavity walls insulated, the material used appears to be polystyrene granules. The meter tails (16mm copper) from the meter (in a recessed wall cabinet) drop down into the cavity and continue down for approx. 1 meter before exiting through the inner cavity leaf into the kitchen larder about 40cm off the floor and on to the CU.
Conductor resistance would appear to be fine with a Ze of 0.08 ohms (after I had replaced the iffy MEC).
I know that PVC sheathed and insulated cables in contact with sheet polystyrene will suffer from plasticiser migration. Is there any evidence of this effect regarding the granular form?
I have noted this as a Further Investigation Required on the EICR.
I have seen many instances of power cables in lofts smothered with 30cm or more of insulation and just torn back around downlights. The Contractors install the insulation are now supposed to be licensed but still have no appreciation as to the effects on cables and accessories and in my opinion this just is not good enough. Surely an insulation material should be fixed to the underside of the rafters not on top of the ceiling over cables which also makes inspection of connections a rather unpleasant and risky affair.
 20 March 2013 10:32 AM
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normcall

Posts: 8144
Joined: 15 January 2005

If it was a grant job, then the cavities were inspected prior to filling with insulation. Naturally, these cables did not exist at that time.
The granules are very good insulators, but I can assure you that the cable insulation will end up with a pitted surface and down to bare metal. Just don't go foraging amongst the insulation to feel where the cables go. Apart from the polystyrene sticking to your skin, shirt and overalls, the bare stuff can be quite a shock. You only do it once.

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Norman
 20 March 2013 07:12 PM
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Phased

Posts: 18
Joined: 10 September 2006

I certainly have no intention of poking around in the cavity, as you suggest it could be a hair raising experience. The tails predate the cavity insulation however so the survey was'nt up to much if it was done at all.
Hey Ho. Have you actually come across affected cables yourself and is there any indication as to how long it takes for serious damage to occur?
I have just done the EICR (no previous certification) and rectified some code 2 recommendations replaced the aging wirable 3036 fuseboard (she would'nt have a clue as to rewiring a fuse but she can press a button) and a rewirable supply isolator, so she has just spent £700 and I don't want to pressure her into more outlay unless it's essential for safety reasons (she did request the above work to be carried out). It probably would not amount to much I know, a bit of trunking, new tails, a couple of service connectors and 2 or 3 hours but thats still £100.
 20 March 2013 09:59 PM
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aligarjon

Posts: 2868
Joined: 09 September 2005

I pulled some out a month ago that i upgraded, they were original tails from the early 80s. polystrene balls everywhere. There was evidence of minor pitting on the insulation but nothing that looked anything like dangerous. (apart from the tails that i removed that only had one layer of insulation )

Gary

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Specialised Subject. The Bleedin Obvious. John Cleese
 21 March 2013 04:16 PM
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mikejumper

Posts: 1746
Joined: 14 December 2006

Originally posted by: Phased
I have seen many instances of power cables in lofts smothered with 30cm or more of insulation and just torn back around downlights. The Contractors install the insulation are now supposed to be licensed but still have no appreciation as to the effects on cables and accessories and in my opinion this just is not good enough.

I foresee a lot work for us being created for us by insulation installers.
I spent this morning pulling out several downlights most of which had serious heat damage to the cables and transformers, all will need renewing.

It's a bungalow.

There were 3 layers of insulation in the loft:

The original thin layer had been torn back around the downlights.
A later thick foil wrapped layer and a third very thick layer had both been laid straight over the open chassis downlights.
 21 March 2013 04:54 PM
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Jaymack

Posts: 4668
Joined: 07 April 2004

I've mentioned before on this forum, the spewing of polystyrene balls when a old wooden, Wylex fuse box was opened; and a room ventilation grille!

Loft insulation? Called out a few months ago, insulation layers from the freebie brigade, laid this on top of a wooden door, that the householder had stored in the loft. It was just lying on the ceiling beams; unfortunately, it was lying on lighting cables, that were lying in turn on the steel grippers for a joint in the beams. The householder wondered why switching the upstairs lights, tripped the RCD! But on the +ve side ............ work for the boys.

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