Earth rod.


Postby chickenhawk » Sat Sep 20, 2008 12:24 pm

My home is covered by a tt earth system. I was recently doing some groundwork and discovered that my earth cable had come disconnected from the rod. This did not seem to effect the wiring in the house. I took the oportunity to replace the rod with a new one. The problem is that when i reconnected the earth cable to the rod my 100ma breaker trips and won't reset as long as the rod is connected. It works ok when the cable is disconnected. This seems to me that my home now has no earth cover. Am i wrong and has anyone any suggestions as to what may be the problem and how to rectify this?

N
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Joined: Sat Sep 20, 2008 12:18 pm

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Postby ericmark » Sat Sep 20, 2008 2:46 pm

I think we should start with how it works.
First RCD:- If power going in is the same as power going out then nothing must be going else where so nothing trips. If however power going in does not equal power going out then it must be going else where i.e. to ground so it trips.
Next Earth:- If all items with metal are the same voltage what ever that voltage is we get no shocks but if we get two different voltages we will get a shock.
Result:- If a single item goes wrong and there is no earth then we will not get a shock this is how the shaver socket in a bathroom works. If however with no earth two items go faulty then the faults can be at different voltages so we will get a shock.
So we use an earth this means if only one item goes wrong it will trip the RCD or blow a fuse and so make the whole house safer.
However if the earth becomes disconnected we will not straight away get a shock it needs a second fault before that happens.
You most likely have one fault and although this has not caused a problem to date with out that earth wire any second fault can cause shocks so the fault must be found and corrected.
What you have is unusual as normally water pipes and gas pipes give us an earth even when the proper one becomes disconnected but with so much plastic this is no longer always the case.
To stop this happening are at least reduce the chance all domestic electrical systems are to be tested every ten years or change of occupant I strongly advise you get a periodic inspection report done to test the earth rod and to find any other faults.
You will get loads of code 4 fails which only means not to latest regulations but any code 1 or 2 fails need redressing.
The meters used are so expensive it is not a DIY job. I will tell you how it’s done if you want but at around £80 just to hire the meters and also if used incorrect they can give people shocks so I would think better to get some one in to do it.
Eric
ericmark


Postby TOPSPARK » Mon Sep 22, 2008 6:58 pm

By disconnecting the earth cable from the earth rod your house has no earth so the fault has no fault path back to earth .I would strongly recommend you call in a qualified electrician and have a full periodic inspection and test done on your house immediately so the fault can be found and rectified and there is no risk of electric shock
regards
Topspark
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Joined: Fri Jul 25, 2008 9:44 pm


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