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Roger Munford avatar image

Advice sought on Distribution in remote African Village

I am assisting in an off grid solar installation with batteries in a remote African village. The compound is about 200m in length and has about 12 small buildings. Half the buildings are for a research centre with quite a sophisticated laboratory and the other half are a health centre for the local population. There is a generator on site but it is very unreliable, expensive to run etc. A doctor is financing the installation and a UK solar installer is doing it for free even contributing our travel expenses.

Before we even start on the solar we will need to upgrade the existing wiring which has been installed ad hoc as the compound grew. It is basically a two core supply with no earthing at all. Each building has a small distribution board with several 25A mcbs, one lighting and the rest leading off to sockets which are plastered into the walls. We would like to introduce RCD protection but the administrators are very much opposed to any change in the wiring - well it has been working all this time without problem. However if the solar is successful more sockets will be added for phone and light charging and more exposure to people.

The effort to install an extra conductor throughout the compound and to each socket would be immense.

If we did nothing and installed the solar/battery system (quattro based) without any earth as it is now with the generator, would the system work OK?

We could install a TT system with earth stakes at the inverter and at each distribution board.

We could install a TN-C-S system linking Earth and Neutral togeher at the inverter and breaking them out in the distribution board.

If we made any changes we could only do a small amount so we would be leaving a partially changed system and there is no guarantee that the work would ever be completed so the wiring could be in an inderterminate state and we want dont want it to be worse than it is now.

Any thoughts on this dilemma would be gratefully received.

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Piet Roskam answered ·
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Piet Roskam answered ·

No earth is extremely dangerous! 25A Mccb doesn't make me happy as well. If you have an unearthed system you need earth fault detection like in mines, which is not the same as an RCD. TT or TN-S or C depends on the earth resistance, but TT is not really advisable in a compound.

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kai answered ·

Purely from a functional perspective, no earth would be somewhat similar to a system installed on a vehicle, no?

On the safety side, maybe other people who have been on similar projects would be able to advise on the acceptable (as opposed to "best") practice regarding electrical earthing in retrofit/brownfield scenarios.

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Hi Kai, the big difference with a car is the voltage, which is at the safe side. 230 is not so you need other applications to make it safe again.

i was thinking of an inverter system installed in an RV or boat, where the output could be 110 or 230v. the point was it would be functional - safety is a separate issue.