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PE advice by Napit (hot tubs)

ebee

There is an article in PE and I have just received it via email.

I am disappointed that the article seems to suggest that it contains all you need to know yet no mention is made of earthing systems

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    mapj1: 
     

    Very low electrode resistances are not always good, nor is it always safe to omit the RCD and rely on a fuse or MCB  if you have them.

    Mike

     

    And vice-versa … in a TT system if you take the simple path for the Zs loop through the main consumer earth electrode resistance Ra (or in a TN system, the supplier's earthing terminal only) as the “worst case” for automatic disconnection, it's not always safe to assume it's the “worst case” for prospective earth fault current once supplementary electrodes are connected. Yet in TT systems this is often ignored “because the RCD does the job” in an earth fault …

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  • 0

    mapj1: 
     

    Very low electrode resistances are not always good, nor is it always safe to omit the RCD and rely on a fuse or MCB  if you have them.

    Mike

     

    And vice-versa … in a TT system if you take the simple path for the Zs loop through the main consumer earth electrode resistance Ra (or in a TN system, the supplier's earthing terminal only) as the “worst case” for automatic disconnection, it's not always safe to assume it's the “worst case” for prospective earth fault current once supplementary electrodes are connected. Yet in TT systems this is often ignored “because the RCD does the job” in an earth fault …

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