New House, Odd earthing arrangement?

[Aragorn84]

We've just moved into a "new" property, built in the 1950's.

The electrics will need some updating in the near future as theres a lack of RCD's and the main CU is an old Dorman Smith with the thermal-only breakers.

I'd like to have it modernised, and I'm probably going to have to get a full inspection done as theres some suspect wiring to some outbuildings that will almost certainly need redone, but my main question was about the main earthing arrangement.

A photo of the meter and cutout:

https://www.dropbox.com/s/nghhdy1j2uwzm1b/IMG_20130716_101410.jpg

The incoming supply cable looks like MICC or similar, i cant see it that well as its behind the meter board, but its copper clad and has a screwed fitting on the end, from which emerges two (rather thin!) wires, one goes to the cutout/fuse, and one to the neutral terminal on the meter.

The earth from the two CU's are the two grey (they've been painted) wires in the centre of the pic above the meter, which appear to be attached to a pipe clamp of the sort you usually see bonding water pipes, which is attached to the supply cable...

Is this a normal/acceptable way of earthing to the sheath of a supply cable? Or should i be contacting the DNO to have it upgraded/fixed?

Also the wires emerging from the MICC seem very thin compared with the meter tails etc, is this normal?

Cheers
Kevin

 

[Aragorn84]

For completeness, some pics of the CU's:

https://www.dropbox.com/s/uz0q8qu1o5kaohz/IMG_20130716_101427.jpg

https://www.dropbox.com/s/n917s3t4vd02sv6/IMG_20130716_101439.jpg

 

[ericmark]

The thin cables are likely only single insulation where the thicker are double insulated and the taking of earth from the incoming supply is quite normal.

However I have seen DIY swapping from TT (earth rod) to TN with clamps likely to crush the inner cable.

If it were me I would ring the DNO as ask what type of supply you should have. They must tell you and often they can't so they have to send out some one to check. When they arrive you can query the cable types.

However if you are going to change the consumer unit maybe better to do that first so if the electrician cuts any seals they are replaced at the same time.

 

[OwainDIYer]

Also the wires emerging from the MICC seem very thin compared with the meter tails etc, is this normal?

Yes, supplier's works aren't covered by BS7671.

And smaller conductor sizes can be permitted with MICC because of the different thermal performance of the cable compared to PVC/PVC.

 

[westie101]

I would suggest that if it is on a party wall, this could be a loop from next door.I have seen them done in MICC.

So it is worth gettig the DNO to visit to check it through, they may even replace the loop

 

[JohnW2]

So it is worth gettig the DO to visit to check it through, they may even replace the loop

What 'excuse' do you think one should use in order to get them to visit?

Kind Regards, John

 

[westie101]

What 'excuse' do you think one should use in order to get them to visit?

1/ the fact that the "N" on this keyboard is a bit iffy!!

2/ Looks as though the earthing clamp is a poor connection, check the loop impedence see what that is, it could be high or cut-out looks in poor condition.

 

[Adam_151]

The electrics will need some updating in the near future as theres a lack of RCD's and the main CU is an old Dorman Smith with the thermal-only breakers.

They arn't actually thermal only breakers, they do have a magnetic part as well, even if you do need a somewhat unreasonably small (for a domestic install) zs value for a fault to trigger it

Manufacturers data sheet: http://www.dormansmithswitchgear.com/tec_support_downloads/mcb/Loadmaster_datasheet.pdf

Theres loads of them still installed, about 30-40% of the rings I test supplied from these breakers fail either on excess zs or cpc not adequatly sized (remember that these were around at the same time as 2.5/1 twin and earth) even using 2.5/1.5 you start to get into difficulties of the zs is close the max permitted IIRC.

 

[Aragorn84]

Thanks for some useful pointers.

Its not quite a party wall, but its very close to one, its in a small alcove under the stairs, beside the party wall, and the cable also seems to go upwards into the wall, which might also support the fact that its going next door, rather than to the street.

I shall see if i can get the DNO out to have a look. Does the DNO have a specific line to call for this type of thing, or shall i just ring up the suppliers customer services line? I believe the DNO and supplier are the same here anyway (Scottish Power).

Would it be possible/sensible to get them to install an isolator at the same time? It would make changing the CU in future easier i guess?

 

[westie101]

I believe the DNO and supplier are the same here anyway (Scottish Power).

they are two separate businesses, the DNO part is SP Networks I think

 

[RF Lighting]

That pyro looks really small, and the earthing isn't great. I'd certainly get the DNO to have a look.

Just ring up the DNO and tell them you're not sure the supply / earthing arrangement to your property is safe, and they'll send an engineer out to take a look.

 

[Aragorn84]

That pyro looks really small, and the earthing isn't great. I'd certainly get the DNO to have a look.

Just ring up the DNO and tell them you're not sure the supply / earthing arrangement to your property is safe, and they'll send an engineer out to take a look.

Cheers.

I've noticed the lights in the property seem to flicker a lot, regardless of wether they're on the lighting circuits, or plugged in lamps or the halogens in the kitchen counters (which are powered from a seperate CU to the main lighting). Sometimes it correlates with turning a load on ie the kettle, but much of the time it doesnt seem to, or it does it with much smaller loads that you wouldnt really expect it to (like turning on the TV) so theres certainly something not 100% with the whole arrangement!

 

[Aragorn84]

As a follow up to this, had scottish power out to look at it today (they booked it as an emergency callout and the guy turned up at 8am )

He said that it was typical of installs in this area, and the underground supply came in next door then was linked across with pyro, but that it was odd that it didnt have a proper service head or earthing block.

He hooked up his loop tester, which recorded what looked like 0.25Ohms, between the earth clamp and incoming feed and he said the earth was decent. He then attempted to disconnect the wires from the earth clamp to check the earth wasnt being sourced thru the bonding etc, but the screw was siezed and he didnt want to damage it.

He said it was really due an upgrade so would book it in for one, but that it might take a few weeks to sort out, then went on his way after speaking to the neighbour and getting their details to sort out access.

Hopefully they'll sort the upgrade out fairly promptly!

 

[securespark]

Good stuff!