Measuring / testing earthing rod impedance

[Softus]

I've just seen an electrical system that has an earthing rod. I believe that this makes it a TT supply type. The earth cable appears to terminate inside the CU; there's no separate MET.

This is my friend's parents' installation, and they're quite blasé about the whole thing, but he wants to know that the rod, and the earthing path, is operating correctly.

I'm a competent and cautious tradesman, but not an electrician. Can anyone point me towards a description of the correct process for measuring whatever I need to? Or am I better off asking a professional to conduct (no pun intended) the test?

 

[JACKC]

Get a copy of Guidance Note 3 Inspection & Testing and read page 52. This is not generally a DIY job as involves an earth loop impedance tester which most DIYers don't have. There is a whole list of variables which can affect the readings and you need to know what type of operating time etc of RCD. Also involves live testing with earth disconnected from C/U leaving house unprotected whilst testing.

 

[Softus]

Thanks JACKC. I'll read the Guidance Note, but the equipment costs aren't justified by the needs, so I'll find a local electrician who can do it.

 

[Dellsmp]

Good call Softus, He'll also advise if there is the required rcd on the cu and whether any extra rods or bonding is required. The actual tests on the rod/s arent difficult, but your right the test kit is expensive, and you might even get a certificate