EV charger installation and fuse upgrade questions

QrizB

@lohr500 would you be happy to share your incomer photo here? And do you have a photo of your pole-mounted transformer?

You're right that I can't see how you could be on a looped supply, but it could be that the transformer feeding your house is only a 60A one.

lohr500

https://forums.moneysavingexpert.com/discussion/comment/82101063#Comment_82101063

Thanks for the reply @QrizB

I'll take a photo or two of the actual transformer and transformer/pole wiring tomorrow once we have some daylight. There is a fuse holder on the pole, but I'm not sure if it is marked up in any way. I might be able to get some details off the transformer and fuse holder by using my binoculars or spotting scope.
I can also try to figure out if it is indeed a single cable that is coming overhead from the transformer to the gable end of the house. Or if it is infact a bundle of cables.

I suppose it could be a 60 Amp transformer/fuse on the pole and at some point prior to us buying the house in the 1990's the house fuse has been changed to 100 Amp. Also, we had an Eco7 meter with an RTS switch fitted when we moved in, so perhaps they changed the fuse at that point in time.

Is it conceivable that in a protective multiple earthing network, the neutral and/or earthing from the transformer high and low voltage sides could be routed directly to physical earth around the base of the pole?
And then the neutral side of the incomer also gets buried in the earth outside our house? I can't imagine they would have buried a separate neutral cable all the way back to the pole from outside the house, although I guess it is possible.

Here's a photo of the incomer and associated wiring :

Permanent live from the meter and neutral from the meter go out through the wall to the Tesla Gateway and then return to the henley blocks. 5th port on the meter doesn't go through the Tesla Gateway. It goes directly to the now redundant off-peak consumer unit.

pete-20-11

https://forums.moneysavingexpert.com/discussion/comment/82100956#Comment_82100956

Do you have an isolator switch immediately after your smart meter?

If not, best to get the DNO to change the fuse and fit an isolator at the same time.

That will then mean the EV installer can safely isolate the power to do their work.

Otherwise they'd have to pull the main fuse (which they shouldn't do) or co-ordinate with the DNO to get them to do that at the same time.

lohr500

https://forums.moneysavingexpert.com/discussion/comment/82101063#Comment_82101063

And here are some photos of the transformer. From the size/style of the transformer is there any way to tell what it might be rated at? I can't see any data plates on the transformer or the fuse box housing.

On closer examination, the original info I provided was incorrect :
There are two inputs to the transformer taken off the outer two high voltage cables.
One output from the transformer runs down to the fusebox on the pole then back up the pole to the cable heading off to the house.
BUT there is a second output from the transformer which also heads off to the house. I'm guessing this must be the "Neutral" side of the transformer. So the cable to the house actually contains both live and neutral wires.

The transformer is also earthed by means of an earth wire running down the pole.

The mystery now is what is going on with that thinner cable which is attached to the neutral side of the main fuse box incomer in the house.

As per my original thoughts, could this be a neutral feed going to earth as part of the protective multiple earthing installation, or is it in fact a redundant loop through which is terminated somewhere underground behind then house??!!

Thanks again for your input.

QrizB

I'll observe that that's quite a small transformer, as pole-mounted transformers go.

We've got folk here who have previously worked in electrical distribution; hopefully one of those will be along with their thoughts on the transformer's capacity!

Sorry to ask for more photos, but can you get a better picture of the cut-out (the black Bakelite box with the DNO fuse) in your house? I'm wondering whether the mystery "extra" cable is part of your supply after all, and isn't going anywhere.

(The other possibility that comes to mind is that your house has - or had - some sort of outbuilding that was fed by that cable, with a separate meter, and it's now redundant & disused.)

itm2

https://forums.moneysavingexpert.com/discussion/comment/82101328#Comment_82101328

There isn't an isolator but there is a Henley block between the meter and the 2 consumer units. I was thinking that the electrician would do the EV charger install before the DNO does the main fuse upgrade, as the consumer tails also need to be upgraded from 16mm to 25mm before the DNO upgrades, and this will need to be done by the electrician, so it would make sense to do that and the charger installation at the same time.

MWT

https://forums.moneysavingexpert.com/discussion/comment/82101446#Comment_82101446

I would be inclined to check that UKPN will agree to a 100A fuse before doing the other work…

They are one of the few that were still doing it, but that may have changed, and even if they are generally willing to do it, your particular grid connection may not be able to support it.

lohr500

https://forums.moneysavingexpert.com/discussion/comment/82101419#Comment_82101419

Extra photos :

The thinner black cable leaving the DNO box runs back to the same hole in the house wall where the incoming cable enters, then runs round the side of the house and disappears through the concrete.

I did some Googling and found some info about how the neutral line can go to earth in some installations. It's either this or perhaps a looped feed to some long lost and forgotten outbuilding with its own meter.
The strange thing is we have an old aerial photo from 1966 showing the farmhouse prior to modernisation.
In 1966 the area where that thinner cable goes under the concrete didn't exist as at that point in time the side of the house was built right into the hillside. So the cable must have been set in concrete around the mid 1980's when the house was modernised. There's no signs of any outbuildings on the 1966 photo and I know for sure we don't have any outbuildings now.

I've asked the DNO if they have any records of a looped supply and/or if there is a possibility that that neutral may go to ground.

A bit of a mystery.

QrizB

If the thinner black cable was an earth connection, it should really be green-and-yellow striped (like your actual earth connection on the cutout).

Is there any writing / printing on the cable from the cable manufacturer to tell you what sort of cable it is? It could be 2- or 3-core SWA, for example? They're usually printed every metre or so, and you've got enough exposed cable that it should be visible.

lohr500

https://forums.moneysavingexpert.com/discussion/comment/82101690#Comment_82101690

Great idea 👍️ I've looked, but sadly no identification on the cable other than CABLES AND PLASTICS LTD LEEDS MADE IN ENGLAND.

Whatever it is, it isn't a neutral flowing to earth as if I move the energy monitoring CT Clamp onto it, it shows zero watts.
If I put the same CT clamp on the neutral wire in or out of the meter, then I get a usage reading on the energy monitor display. Rightly or wrongly from this test, I'm concluding that the neutral must be returning back to the pole/transformer via the second wire in the overhead cable.

I would love to remove the cover of the DNO box to see how it is wired internally, but curiosity isn't going to get the better of me and I am leaving well alone!!! Not to mention the risk of being accused of tampering!!

I guess it's a waiting game now for the DNO to get back to me confirming if they have any records of a looped supply. Hopefully they will respond and advise on next steps to get the 60 Amp max house rating increased.

If it is just a case of it being a looped supply (now going to nowhere!) then I wonder if they will come out and disconnect the cable in question and/or agree to increasing the house rating?
If it is some form of extra earthing cable related to th protected multiple earthing network e (albeit with the wrong color coding) then it would be good to know for future reference.