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Very low Ra reading disappears when connected back up.

aligarjon

Hi Guys

I had some very strange readings today when doing an EICR.   Property is a semi detached cottage in a very rural location. Over head supply. 

The first thing i noticed when i arrived was a piece of angle iron driven into the ground outside the front door with a corroded 10mm earth cable bolted to it exposed for all to see.

The consumer unit is located just inside the front door in a cupboard and i can see the earth cable going out through the door frame.  I disconnected it at the CU and got an Ra reading of just over 2 ohms so i am obviously amazed. I reconnect it to the CU to get a PFC reading etc and the Zdb is nearly 300ohms with the original earth reconnected. I disconnected it again and got just over 2 ohms again. Reconnected it and got around 300ohms.  

This is a new one on me, does anyone know what could be going on ?

Cheers  Gary

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    Reply to both.  Yes i measured it like a loop test. Basically disconnected earth cable from board and put live and neutral prongs onto main switch terminals, or in this case an up front rcd.  I don't get how i can get 2 ohms then it disappears when i connect it back to the earth terminal in the consumer unit.

  • 0 in reply to aligarjon

    Live and Neutral prongs onto switch terminals? That is more likely to read P.S.C.C. rather than Ra of the angle iron. Or you are measuring L to N on a loop test setting? Live lead to L in house and N lead to earth electrode is required by my loop tester for the earth rod Ra.

    Z.

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  • 0 in reply to aligarjon

    Live and Neutral prongs onto switch terminals? That is more likely to read P.S.C.C. rather than Ra of the angle iron. Or you are measuring L to N on a loop test setting? Live lead to L in house and N lead to earth electrode is required by my loop tester for the earth rod Ra.

    Z.

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