MAINS EARTH WIRING


Postby dbdunce » Wed Feb 17, 2010 5:39 pm

I am trying to physically trace the 'earthig' wire system in a 1960's built house.
The sockets all have the correct earths back to an earth bus in the fuse boxes (which have the old fusewire type fuses NOT consumer unit).
The fuse boxes (2) have their earth buses connected together and a wire runs from this back to the meter board where it dissappears into the primary power cable running into the house. It does this without passing through anything on the meter board.
I have found various earthing straps connecting water pipes in both the bathroom and the kitchen but these are only connections between pipes and are without any earth grounding rod connection. My incoming mains water pipe is plastic so I'm not sure what these are achieving.
My central heating pipes (all copper) are burried in the concrete floor of the house, and I am wondering if they are relying on these to act as an 'earth' to ground.
Is the whole electrical system relying on the rather flimsy single cable connected to the mains inoming bundle. Should I be adding a ground rod buried earthing strap to the pipework and/or the mains earth bus?
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Postby kbrownie » Thu Feb 18, 2010 12:16 pm

Your incoming supply could well TN-S or TN-C-S. does the fuse box have an RCD connected?
If it does your earthing arrangement may be TT but I think it,s one of the above, which means by one way or the other the supply company is offering you an earth.
The pipes are cross bonded for your protection against any potential shock. Crteating a equipotential zone
Some useful links
Google "en.wikipedia.org/wiki/Earthing_system"
Google "en.wikipedia.org/wiki/Electrical_bonding#Equipotential_bonding"
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Postby dbdunce » Fri Feb 19, 2010 9:16 am

Thanks for that. There is no RCD in the system. I will look at the google refs. you gave and work out which system I have, but I think you are right in that the earthing is 'provided by the power supyling company' and is in the incoming power suply cable. My only concern is that this looked rather thin and flimsy when compared with the main part of the incoming cable supply and would have expected a wire of the same sort of diam.
Having said all that the fuses certainly 'blow' at the expected time in response to a fault.
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