One of the jobs in need of doing shortly is the replacement of my Wylex
rewireable fuse consumer unit. Nothing actually wrong with it, but it
only has six ways and I am going to be needing eight in the near future,
so it seems like a good time to bring it up to date.

This brought about an investigation of the earthing setup. Never having
had need to look that closely at it in the past, I had not done a
detailed study of what was there, and had probably made a few
assumptions! A quick check over tonight raises some interesting points...

First assumption - Being a TT System (overhead power delivery) it will
have RCD protection. Having looked close up at said "RCD" I am now not
so sure. Have a look at the following (out of focus) pictu-

http://www.internode.co.uk/images/cb.jpg

Is that likely to be an RCD? Or is it more likely, as I now suspect, an
old style ELCB?

The words at the top read "Test this protective switch often by pressing
the yellow button", the words above the switch simply show "500V 50~", &
"60 AMP". It's made by Crabtree. Nothing else that I can see written on
it - no mention of a trip current. That feed through earth wire from the
CU looks a bit suspect as well!

The Henley block you see in the photo splits the tails from the meter,
one set go to the item in the photo - the second set go to a much newer
MK 30mA RCD that ultimately feeds the out buildings.

The second point of interest is the actual earth itself - So far the
only earth connection I can find is to the incoming (steel/iron) gas
main. Nothing that I have yet found seems to connect to the water main,
and as for an earth spike - if there is one, it is well hidden. (don't
even bother asking about suplimentary or equipotential bonding!) Not
sure how common this was/is on 50's properties? While the gas main might
be a resonable earth (not tested it yet I do know that there is no
plastic in it for a good 20m minimum) not sure I like the idea of
relying on only that.

(the outbuildings do have their own earth spike adjacent to them - I
have not yet verified if this is connected back to the house earth as
well - although it is certainly not isolated from the SWA armour on the
feeder cable).

Hence an upgrade to all things earth seems like a good plan.

How many earth rods, and to what depth would be recommened for a heavy
clay soil?



--
Cheers,

John.

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