Hi could anyone point me in the right direction for the maximum permissible resistance reading for earthing rods?
- Aug 30, 2011
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Depends on the (RCD) Residual Current Device thst follows,as your unlikely to meet max ZS on mcbs alone, however the iet say above 200 ohms may not be stable, so less than 200 and as low as possible.
- Dec 18, 2011
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It depends very much on what RCD you are using, or even If you are using one.
For example, if the RCD is 500mA then a max Ra of 100ohms is classed as acceptable. See table 41.5 BS7671.
If you intend to use the rod as the sole means of ADS then it probably needs to be sub 1ohm. I realise this sounds silly, but I'm just making the point that more information is required to give an accurate answer.
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