External wall insulation and mains supply

ThisPete: 
 

I'm having external wall insulation installed on my house, and the mains supply to the house is via an overhead cable. The insulation installers have put the insulation over the mains supply cable, i.e. where it's clipped to the wall between bracket and meter box. The DNO is Western Power. 

My question is, is covering the mains PME cable with 90mm of insulation acceptable practice? 

Thanks, Pete

Hi Pete, welcome to the institute of enginering technologists forum,the pme earthing arrangement isn’t really relevant so rest easy on that one, if you could post a photo of your concerns they do paint a thousand words :)

PME is unlikely to be relevant, but this MIGHT be a bad idea for other reasons.

Firstly the thermal insulation will reduce the current carrying capacity of the cable which MAY then be insufficient.

The now concealed cable could be damaged by someone unaware of its presence who drills into the wall. This can result in the death of the person, setting light to the building, and expensive repairs.

The concealed cable is vulnerable to tampering to facilitate theft of electricity. 

I would approach Western power at an early stage.

If the cable belongs to Western power they will know if it is 35mm2 or 25mm2 or another, perhaps imperial, older  size. They should also know the fuse rating in your house, and therefore the maximum load you may draw.

These two pieces of information  allow the suitability of the cable to be assessed - anything else is just guesswork - it may be slightly oversized,  and run cold at your maximum demand, it may be only just about OK in fresh air, and overheat significantly in normal use once lagged.

Their daytime general enquiries number is  0800 096 3080 you should be sitting comfortably and ready to allow a bit of time to get past the “have a nice day”  screen before you get to someone technical who can advise.

Mike.

The Supplier‘s cable must not be concealed without their permission. You should contact them for permission / advice before the work begins. They may wish to temporarily locate / protect their cable during the work, then re-fasten it to the new outer safety later. 

Regards,

Alan. 

The name Weird is “The Institution of Engineering and Technology”.

Many thanks to all who've commented. As people have stated, and further discussion with WPD has confirmed, covering the WPD cable with insulation/cladding is in breach of the WPD/DNO regulations. 

While the DNO side of the meter/consumer unit is not really part of the IET Wiring Reg, being able to find some good practice guidelines would be really useful to point my electrician at! 

ThisPete: 
. . . While the DNO side of the meter/consumer unit is not really part of the IET Wiring Reg, being able to find some good practice guidelines would be really useful to point my electrician at! 

I am not sure what you are expecting your electrician to do, or us to recommend. The good practice guidelines are to leave it alone, and involve the DNO to have it relocated. Your electrician is likely to be neither competent nor authorised to work on the “supply side” of the tariff metering equipment. 
 

Regards,

Alan. 

I agree get the DNO to come out and have look unfortunatley they will probably charge an excessive amount of money to do it. But it's the only safe option. Thinking about it some more they mite only make a nominal charge because your having insulation added and that satisfys all sorts of greeny issues so ask them keep your fingers and toes crossed hope for the best

The insulation installers have put the insulation over the mains supply cable,

Not very professional of them…………… You would have thought that they would have received some accreditation to comply with Building Regulations to self certify and during that process, had been advised of the position regarding DNO property.

Have they done a runner or is your electrician trying to defend their work?

Regards

BOD

I fail to see why the DNO's cable cannot be left uncovered.