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Earthing and bonding, possible island mode, why separate earths.

Alan B

Looking at a domestic install, have only looked at earthing in the meter cabinet so far.

It's a single phase installation with solar on the roof of a detached stables. At the moment not quite sure how the solar is connected in to the main system, needs further investigation tomorrow, but I don't think it's likely to support island mode.

The bit that's confusing me at tge moment is earthing in the meter cabinet.

There's a TNC's earth coming of the supply, going in to the house

There is also a TT earth connected in to a Henley block along with a bunch of what I assume are bonding conductors and another main earth going in to the house. But the TT earth and the TNC';s earth are not visibly connected in the meter box. They may be connected somewhere else, still need to investigate. But why would the installer separate the two earthing systems? Even if island mode is supported in the installation from what I have read just line a neutral are switched and all the earthing remains connected.

I am installing an EV charger. At the moment my plan would be to a bit more investigation but ultimately will just connect the TNCS and TT earth together and to the EV db.

Any thoughts on the arrangement and best course of action.

Thanks

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    Hi All

    Thanks for the input. Turns out there wasn't anything as cleaver as island mode installed, just a very bad conversion from TT earthing to TNC-S. The installer had made the TNC-S connection through to the main DB, but only to the main DB using a 6mm cable. The TT earth was connected only through supplementary bonding in the bathroom. I don't think the stables are used for live stock, but couldn't gain access to make further checks on my last visit. Strange arrangement where they are using power from the house and also providing solar power to the house but not owned by the householders. House was sold without the attached land and stables.

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  • 0

    Hi All

    Thanks for the input. Turns out there wasn't anything as cleaver as island mode installed, just a very bad conversion from TT earthing to TNC-S. The installer had made the TNC-S connection through to the main DB, but only to the main DB using a 6mm cable. The TT earth was connected only through supplementary bonding in the bathroom. I don't think the stables are used for live stock, but couldn't gain access to make further checks on my last visit. Strange arrangement where they are using power from the house and also providing solar power to the house but not owned by the householders. House was sold without the attached land and stables.

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