Garden pump on PME

[JohnW2]

The only concern of real importance is that the retail unit's water supply still comes from my cottage, ( they were once both owned by the butcher ) and there has to be a metre of "isolation" ( plastic pipe ) ...

If, as I presume is the case, you have that one metre (or more) of plastic pipe, then I presume that is no longer a matter for concern.

...their copper pipework which I assume is bonded to their ground rod.

I'm sure that we must have been through this before, but I don't recall any explanation as to why this really is a cause for concern. Even if the full supply voltage were applied to it, a domestic TT electrode is unlikely to allow much more than 5A or 6A to flow into it (or through any associated cables). Can you remind me what the concern is?

Of course, you have more general concerns about TN-C-S earths (other than those relating to the adjacent TT property). Do you, for example, have any outside taps and, if so, are they 'isolated'?

Kind Regards, John

 

[bernardgreen]

Even if the full supply voltage were applied to it, a domestic TT electrode is unlikely to allow much more than 5A or 6A to flow into it

Connecting my Neutral to the retail units ground rod could, in the event of a network fault on my Neutral, lift the CPC of the retail unit well above 50 volts. There is the possibilty that some time in the future the retail unit may upgrade to new PME supply from the street cable outside their premises. That cable is not the same as my supply cable and hence any joining of the two CPCs ( via pipes etc ) would be connecting two separate supply network Neutrals via conductors inside the properties.

have any outside taps and, if so, are they 'isolated'?

An outside toilet and taps in the back porch ( were used for washing butcher's tools ) should be isolated. More reason to get the ground rods in.

 

[JohnW2]

Connecting my Neutral to the retail units ground rod could, in the event of a network fault on my Neutral, lift the CPC of the retail unit well above 50 volts.

Indeed, but so what? If the retail unit is properly constituted as an equipotential zone, then everything touchable within the premises should be at the same potential, be that 'well above 50V' (relative to true earth) or anything else.

There is the possibilty that some time in the future the retail unit may upgrade to new PME supply from the street cable outside their premises.

That may be true, but it's rather moving the goal-posts. I was talking about the consequences of a TN-C-S earth and TT earth becoming connected (via pipes or whatever).

.... That cable is not the same as my supply cable and hence any joining of the two CPCs ( via pipes etc ) would be connecting two separate supply network Neutrals via conductors inside the properties.

Even though it's not what I've been talking about, that's an interesting point, that I don't think I've ever thought about. However, I assume it's probably very unusual to have two attached small premises getting their electricity supplies from different network distribution cables.

Kind Regards, John