possible TT system?......Update

[BigJon]

Hi, im heading toward the end of a re-wire so thought id start some testing on the circuits that are completed so far so i tested the PSC got infinity
Tested EFLI, infinity in the 20 ohms and 200 ohms scale, got 175 on the 2000 scale.
although the earth bar is there its obviously not doing anything.
Is it "normal" for the earth bar to be there if it is a TT system,
Just to add the previous main board had its main earth taken from this board and the owner "hadn't had any problems"

PS the existing 16mm earths are mine

Thanks

 

[Spark123]

Did you test the Ze (external earth fault loop impedance) with it disconnected from the installation?
The earth block on the side of the distributors cutout may not be connected to anything however if that was the case then I'd expect them to have not provided it at all.
Probably worth calling them out to it.

 

[Click-Sure]

I've not seen an earth bar for a TT system attached to the suppliers cutout before.

Seems more to me that it is a TN-S system that has had the earth part of the cabel severed.

As the DNO allready provides a means of earthing, it is their responsability to maintain it, so give them a call (well, normally via the electricty supplier) and they will come out to have a look, they'll either repair the break, or more likely in my opinion, convert the supply over to PME/TN-C-S.

Or you could just TT the installation as per usual, but the first option seems much better.

 

[BigJon]

Hi, yes disconnected totally, Im thinking that it isnt connected to anything aswell. It is in quite a remote area so im wondering if it comes from overhead, although cant see any transformers around, not sure how far away they normally site transformers.
I asked the owner to call scottish power out to confirm what type of system it is and whether a pme supply is possible.
just wanted to confirm ive did the right thing in calling them out as there may be a fee involved.
Thanks for speedy reply.

 

[Click-Sure]

As I say, it looks thike they are providing a means of earthing, and it is their look out to ensure it is maintained, so I can't imagine a fee would be payable, I'd argue till I was blue in the face if they tried to levvy a charge!

 

[BigJon]

I've not seen an earth bar for a TT system attached to the suppliers cutout before.

Seems more to me that it is a TN-S system that has had the earth part of the cabel severed.

As the DNO allready provides a means of earthing, it is their responsability to maintain it, so give them a call (well, normally via the electricty supplier) and they will come out to have a look, they'll either repair the break, or more likely in my opinion, convert the supply over to PME/TN-C-S.

Or you could just TT the installation as per usual, but the first option seems much better.

Hopefully they will sort it when they come out, Yes 1st option seems much better, thanks

 

[securespark]

I see loads and I mean loads of these. It looks like you've got a TT supply with a TNC-S head. If it is not labelled as PME, then it could well be TT.

Just because there's a bit of wire there does not make it PME.

As for arguing that the DNO provided it, that will almost probably fail. With this type of cut-out, the earth cable can be attached without special tools or access to the inside of the cut-out (as is the case with more modern cut-out designs).

The DNO will argue till they're blue in the face that they did not provide this earth terminal as there is no PME notice.

Get it converted ASAP: b*gger the cost! It won't be much more than 100 quid.

 

[BigJon]

Hi SS. yes definately going to get it converted, though am i right in thinking if its an overhead supply then pme is not possible?
If it is coming from overhead do you know if the transformer is normally sited next to the house or could it be a fair bit away out of sight of the house?
Theres certainly no labelling, although the incomer is very old so label may have perished
Thanks

 

[RF Lighting]

PME is usually available on most overhead supplies these days. (Providing the DNO has installed it on your part of their network)

I have come across a few cutouts like yours which dont actually have anything connected to the earth block on the head.

The last one I did was a TN-S supply on PILC, using clamps to provide the earth from the sheath of the cable. There was no connection the the earth block.

The transformer might be next the the house, or it might be a few hundred meters away. It depends on now many other houses it supplies, and wether you are the first, last or only house supplied by this TX.

 

[securespark]

Not only overhead TT. There are plenty of subterranean TT supplies out there.

As for label being perished, PME has only been going since the 60's, but to be fair, some are not labelled.

 

[BigJon]

Thanks SS, appreciated

 

[BigJon]

After several calls from the customer to Scottish Power a PME system fitted, Ze - 0.16 PSC 0.66
Spark told customer the readings weren't to his normal high standard but were ok, seem fine to me.
Although its not all good news as tonight in spells every light was dimming ( on all 6 circuits ) in and out, not too much but it was certainly noticable.
On putting the earth loop meter on the isolator mains ( just to get the voltage ) the voltage seemed to go between 235 and 250, This happened for about 15 mins or so then all appeared fine for a few hours then did the same around an hour later for about 5 mins or so, then was fine the rest of the evening.
All connections nice and tight so i dont think that is the problem.
May just be a one off as it never did this previous to the PME conversion.
Being in an secluded area could this just be an isolated case high demand on the grid causing it?

Thanks.

 

[Pensdown]

My lights keep dipping at the moment because the farm down the road is using the grain dryer. If it's also affecting you I will let him know

Just out of interest, how much did they charge for the conversion?

 

[BigJon]

Lol. He got it free of charge, Customer debated that the earth they supplied was not fit for purpose so he's pleased with that.