Earthing through plastic pipe

[TimW]

The black cable is the end of the overhead power line, attached to the corner of the house, coming from a pole across the road. tw

[TimW]

No, it comes from the gaps between the joists. tw

[Robin]

Don't worry about that, it's trivial compared with your earthing.

The news that you have an overhead supply combined with the "dog's breakfast" aspect makes me more inclined to suspect a "DIY PME" installation. That is, someone has come along and connected the earth cable between the incomer and the consumer unit to make it look as if you have TN-C-S/PME when in fact you have TT.

It doesn't follow that you have an exceedingly dangerous setup. And there might be an earth rod somewhere. But when looked at alongside the consumer unit (with it's mix of brands and lack of RCD protection on some circuits) I'd be bothered. I think you should have it looked at. But others will know more and better than me.

In the meantime be careful.

[newshound]

Although *if* it is a reasonably recent installation, the supplier's main fuse or switch may bear the magic letters "PME".

That said, mine did when I moved in, but the earth was not in fact connected to the neutral, but to a fairly feeble looking earth rod right by the front door.

As someone else suggested, a photo of the fuse box and surrounds would let us advise better.

[Tufnell Park]

It is not possible from the photo posted to say definitively what type of earthing system you have here.

You would need to get a competent electrician to determine that.

You may be able to speak to your DNO (distribution network operator) to determine if their network in your area has PME (protective multiple earting) available.

Re Your original question about the 'earth wire' connected to the water pipe, this is most likely to be a bonding connection.

[Andrew]

I wonder why there is an earth cable going into the company fuse block then ?. I thought overhead supply was phase and neutral only and you had to have a separate earthing arrangement.

There is another earth cable coming out of the company fuse block and it droops down but doesn't seem to go anywhere ?. Is this correct ?.

[John Rumm]

Indeed the sticker alone is not solid evidence that the install is actually using the PME earth.

My cutout has the PME sticker, but it would seem that the upgrade to a PME capable supply occurred after the house was previously re-wired.

Hence the installation is TT (as would be typical for many rural properties with overhead supplies).

[John Rumm]

That superficially at least looks like a TN-C-S install. There is a yellow sticker on the side of the cutout, does that say PME by any chance?

If it is as it appears, then the connection to the water main was just an equipotential bond. It still needs to be connected back to the incoming cold supply just after your stop tap if your internal pipework is metal, but it does not pose as serious a risk as not having a main earth.

[John Rumm]

Historically that was the case, but many overhead supplies have been upgraded with PME capability over the years. (sometimes looking at the polls will give a clue - they may have earthing conductors running down the side of every few)

Probably a left over from the now removed time switched CU.

[John Rumm]

I would say if Tim can confirm the presence of the PME sticker (assuming this is a UK installation) on the left of the cutout, there is a very strong likelihood of it being TN-C-S.

To be certain he could, turn off the power, pull the main fuse, and take the cover off the cutout (with the normal warnings about access to live parts etc). A TN-C-S install would have a metal bridge between the neutral and earth terminal blocks in the cutout:

The same style of cutout can be used for other supply types. Say it were TN-S you may see something like:

(Note the missing link, and the separate earth feed from a split concentric cable)

Yup, they should be able to tell you what its capable off even if not what your actual installation is.

I would concur.

[tabbypurr]

It's nothing to do with the leccy board.

NT

[tabbypurr]

You've got a supplier earth with partial RCD cover. So the water pipe conne ction is equipotential bonding only. If the internal piping is metal, recon nect the earth coloured wire to the house metal water piping somewhere near where it enters the house and Robert becomes related.

NT

[ARW]

Although it is the same service head as John Rumm's, John actually has a Ze reading on his. However on the plus side the cut out is sealed and that suggests that the earth is genuine. You need to cut the seal and remove the fuse to access the earth on that service head.

[Robin]

Meanwhile what might help Tim is to know that the relevant function of "Electricity Boards" was transferred as part of the privatisation of the industry to distribution network operators (DNOs). As John has already pointed out they can and do deal with earthing - although they may charge (and will require main bonding to be up to current requirements before they supply PME).

[Robin]

My apologies to Tim for my excess of caution.

And in case Tim hasn't picked up on it, Adam does this shit for a living

- and by all accounts rather well.

[ARW]

It could be a false seal:-). The yellow sticker will say PME on it but that is no guarantee. The OP's only answer is to call his supplier.

[Robin]

I think I was biased by the contrast with the few conversions to PME I've seen where the earth was a short bit of cable to a MET, or to a connector left dangling like

[TimW]

Yes, thanks. Really useful. Given that that board has been put in the porch there in my time and the wiring has been professionally inspected after some alterations since then I will just sleep easy. TW

[Dave Plowman (News)]

How would you define leccy board? The same as your electricity supplier?

If I meant that I'd have said so. ;-)

[spuorgelgoog]

That CU is definately one from someone's bits box!

Owain