Figuring out which earthing system in use, and how to use it

[nuked]

Hi all,

Disclaimer: I'm not a qualified electrician .

I'm trying to figure out what sort of earthing system our house has, looking to replace a very
dated voltage operated RCD and consumer unit with something more recent/sensible (BCO
notified and all that). What's confusing me slightly is that there are two earth leads emerging
from the wall in the house, along with the live and neutral conductors. One of these earths
was/is connected to the "auxiliary earth electrode" of the voltage-RCD and nothing else, the
other goes straight into the CU, whose earth is in turn connected to the "earth continuity
conductor" of the voltage-RCD. With everything disconnected, I get a resistance of around
1.2k-ohms between them, no apparent potential difference between them or neutral, and the
expected between all three and live. The voltage-operated RCD is a Chilton 60A type D,
labelled as "voltage operated earth leakage circuit breaker BS 842".

So, does anyone have any ideas as to what sort of earthing system might be in use here?
TT? and what these earths might be connected to outside the house -- unfortunately the
wiring out here is old and mostly covered in render/paint so it's hard to tell what's going on!
Since we have water and gas supplied in plastic pipes I'm assuming it's not these.

In replacing this dated stuff with something more modern (split consumer unit with dual-pole
RCDs feeding MCBs, plus a couple of dual-pole RCBOs), which of these earth leads should
be hooked up to the earth block in the unit?

I did try calling UK-power who are the DNO for the area, but they happily stated that they
don't keep records on this and that I should ask an electrician..

Your years of wisdom appreciated!

-- nuked

 

[Engineer54]

Don't particually like these tight boxes, they are for one thing mounted above ground level, and are prone to damage. These things also tend to encourage driving rods next to the building walls, which is just about the worst place to drive earth rods, because of all the builders rubble being buried there....

...Much prefer a moulded ground pit which is flush with ground level. They have plenty of room inside, that you can if you wish, set in concrete...

 

[UKMeterman]

And if you use the pit, you have a much reduced surface potential, less likely to kill the family rabbit or dog...

 

[UKMeterman]

Hi,
You may wish to read page 36 of http://www.google.co.uk/url?sa=t&rc...7ICYCA&usg=AFQjCNE2l0U_DO0LzBAuw8RCws-Ivf_vdw the other DNOs have similar comments about domestic amateur radio installs.