EPS

[marshman]

Can a layman tell what sort of supply he has? In an ordinary Victorian semi in an ordinary street, with the original cabling... Looks like a new fuse holder though.
Here's mine, with the cable continuing through into next door.
A

That’ll be a looped TN-C-S.

I would have said that was TNS, but it's difficult to be certain without measurement.

At the moment, I'm operating on the principle of: if a local earth rod is required and the supply is TNC, then convert to TT - but yes, it's a pain here in Wales where you're lucky to find 6" of soil in places, and when you do get a rod in it sometimes reads 400 odd ohms so you need to fjnd a place some distance away for another rod; 240ohms, okay and another...

I'm still ploughing through amd 2 so i don't have an opinion on the new requirements yet...

Yes BUT, as the video I linked to points out, if it is an old house (victoria terrace for example) and has a metal waterpipe this is very likely to feed the whole street and all the other house will likely be TNS or TN-C-S and the metal water pipe will link your earth to their's so you will still be effectively TNS / TN-C-S just with and extra earth rod - you may NOT have converted to TT. As I said it all depends on the individual situation and there is no "one size fits all" solution. Do the wrong thing and there can be all sorts of unseen and unintended effects, and you may end up creating more issues than you solve.

[Stinsy]

The “danger” with installing your own earth rod on a TN supply is that in the event of a PEN-fault your earth rod could become the return path for all electric used by you and everyone else downstream of the fault.

So, can you get the DNO to change this and if so what do you need to get it changed to?

Whilst the risks are probably very low of this ever happening, I prefer the "it cannot possibly happen" way of thinking with electrical installations.

Thanks,

DNO not involved. In a TN supply the DNO provides an earth connection, but you have no obligation to use it.

Previously you could use the DNO-supplied earth OR use your own earth spike. This can be for all, or part of your installation. Eg it was common for a shed, hot-tub, EV charging point, to use its own earth spike while the house used the DNO supplied earth. It was prohibited to use both. The part of the installation using your own earth spike had to be isolated from the DNO-supplied earth.

However the regs have changed very recently and now (it seems) not only can you use both your own earth spike and the DNO-supplied earth, but all houses with a DNO-supplied earth MUST have their own spike in addition. This change has raised a few eyebrows and we will find out more when “Guidance Note 8” is released at the end of the month.

[Stinsy]

That’ll be a looped TN-C-S.

So if I have understood correctly, DON'T have a permanent supplementary earth, but make sure you do have one which is switched in (to the house circuits only) when running off batteries isolated from the mains?
A
p.s. except that our earth doesn't come off the neutral conductor in the fuse installation as shown in the training videos (e.g. but presumably is joined to the neutral via the cable shielding somewhere remote.

Yours is much older than those videos, the earth in your install comes off the sheath of the supply cable. In off-grid mode you MUST use your own earth rod because the DNO-supplied earth could be compromised. Also in off-grid mode you must link earth and neutral at the inverter. This is all easily achieved with contactors (relays). You should also include a timer relay to ensure you’re not constantly switching between grid and off-grid in the event of an intermittent outage.

The point of this discussion is: if you are now permitted to fit your own earth spike in addition to the DNO-supplied earth then you would then be able to rely on your house’s normal earth in the event of an outage. This would simplify your install.

[Marcus]

That’ll be a looped TN-C-S.

I would have said that was TNS, but it's difficult to be certain without measurement.

At the moment, I'm operating on the principle of: if a local earth rod is required and the supply is TNC, then convert to TT - but yes, it's a pain here in Wales where you're lucky to find 6" of soil in places, and when you do get a rod in it sometimes reads 400 odd ohms so you need to fjnd a place some distance away for another rod; 240ohms, okay and another...

I'm still ploughing through amd 2 so i don't have an opinion on the new requirements yet...

Yes BUT, as the video I linked to points out, if it is an old house (victoria terrace for example) and has a metal waterpipe this is very likely to feed the whole street and all the other house will likely be TNS or TN-C-S and the metal water pipe will link your earth to their's so you will still be effectively TNS / TN-C-S just with and extra earth rod - you may NOT have converted to TT. As I said it all depends on the individual situation and there is no "one size fits all" solution. Do the wrong thing and there can be all sorts of unseen and unintended effects, and you may end up creating more issues than you solve.

Yes, hence the need to 'measure' to see what you actually have in the way of earthing, but my point was that the supply itself looks more likely to be TNS to me.

[Stinsy]

I would have said that was TNS, but it's difficult to be certain without measurement.

At the moment, I'm operating on the principle of: if a local earth rod is required and the supply is TNC, then convert to TT - but yes, it's a pain here in Wales where you're lucky to find 6" of soil in places, and when you do get a rod in it sometimes reads 400 odd ohms so you need to fjnd a place some distance away for another rod; 240ohms, okay and another...

I'm still ploughing through amd 2 so i don't have an opinion on the new requirements yet...

Yes BUT, as the video I linked to points out, if it is an old house (victoria terrace for example) and has a metal waterpipe this is very likely to feed the whole street and all the other house will likely be TNS or TN-C-S and the metal water pipe will link your earth to their's so you will still be effectively TNS / TN-C-S just with and extra earth rod - you may NOT have converted to TT. As I said it all depends on the individual situation and there is no "one size fits all" solution. Do the wrong thing and there can be all sorts of unseen and unintended effects, and you may end up creating more issues than you solve.

Yes, hence the need to 'measure' to see what you actually have in the way of earthing, but my point was that the supply itself looks more likely to be TNS to me.

You treat all TN-S as if they are TN-C-S because if a section of cable has been replaced anywhere they’d have converted it to TN-C-S. They don’t notify you of the change and you have no way of knowing.

You’re right that originally that supply would have been TN-S. But now it is likely TN-C-S.

Nothing to “measure” by the way. Earthing method is determined by visual inspection. You could say “Ze is 0.1 Ohms so must be TN”, or “Ze is 20 Ohms so must be TT”, but they are potentially dangerous assumptions.

[Marcus]

Yes BUT, as the video I linked to points out, if it is an old house (victoria terrace for example) and has a metal waterpipe this is very likely to feed the whole street and all the other house will likely be TNS or TN-C-S and the metal water pipe will link your earth to their's so you will still be effectively TNS / TN-C-S just with and extra earth rod - you may NOT have converted to TT. As I said it all depends on the individual situation and there is no "one size fits all" solution. Do the wrong thing and there can be all sorts of unseen and unintended effects, and you may end up creating more issues than you solve.

Yes, hence the need to 'measure' to see what you actually have in the way of earthing, but my point was that the supply itself looks more likely to be TNS to me.

You treat all TN-S as if they are TN-C-S because if a section of cable has been replaced anywhere they’d have converted it to TN-C-S. They don’t notify you of the change and you have no way of knowing.

You’re right that originally that supply would have been TN-S. But now it is likely TN-C-S.

Nothing to “measure” by the way. Earthing method is determined by visual inspection. You could say “Ze is 0.1 Ohms so must be TN”, or “Ze is 20 Ohms so must be TT”, but they are potentially dangerous assumptions.

( Sigh) This is why i usually don't get involved - it always degenerates into pedantic arguments.

Yes it might have been converted to tncs buf it LOOKS like TNS - which us what i said. If you measure it it will tell you what it IS now, not what it might be next year.

If you MEASURE the bond to the water/gas/etc then you will know if it's connected to someone elses electrical earth - not always apparent by looking at a pipe coming out of the ground.

Don't assume anything look AND measure.

[Stinsy]

Yes, hence the need to 'measure' to see what you actually have in the way of earthing, but my point was that the supply itself looks more likely to be TNS to me.

You treat all TN-S as if they are TN-C-S because if a section of cable has been replaced anywhere they’d have converted it to TN-C-S. They don’t notify you of the change and you have no way of knowing.

You’re right that originally that supply would have been TN-S. But now it is likely TN-C-S.

Nothing to “measure” by the way. Earthing method is determined by visual inspection. You could say “Ze is 0.1 Ohms so must be TN”, or “Ze is 20 Ohms so must be TT”, but they are potentially dangerous assumptions.

( Sigh) This is why i usually don't get involved - it always degenerates into pedantic arguments.

Yes it might have been converted to tncs buf it LOOKS like TNS - which us what i said. If you measure it it will tell you what it IS now, not what it might be next year.

If you MEASURE the bond to the water/gas/etc then you will know if it's connected to someone elses electrical earth - not always apparent by looking at a pipe coming out of the ground.

Don't assume anything look AND measure.

I don’t know why you’re getting annoyed. When you call someone “pedantic” what you’re really saying is that you were wrong and they were right but you’re not happy about it.

[Marcus]

Whatever

[marshman]

All of which illustrates perfectly that it is not a simple subject, every install is different and you shouldn't mess with it if you don't fully understand what you have, what you are doing and what the consequences may or may not be.

As has been pointed out - assume nothing !!

[Countrypaul]

Just out of curiosity, following earlier comments, when we had a water meter fitted, the YW contractors removed the old metal stopcock and replaced it with a plastic fitting into which the meter was screwed. Given the water pipe spplying the gouse is copper and earth bonded near the Electricity meter, shoud the earth normally be checked by a sparky if you have a water meter fitted? Our house was completely rewired and a new non-smart meter fitted after the water meter was changed.