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100mA RCDs TT system

Nikkid
Afternoon all,

What is the stance on using 100mA RCDs for TT systems now?

I was under the impression that they are no longer required as long as all circuits were protected by a 30mA RCD within the consumer unit (which in this case they will be).

Just looking for some clarity. 


Thanks! 

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  • 0
    Ian Hildrew:

    Nowadays to reduce the susceptibility to nuisance tripping, good electricians fit every circuit with its own RCBO. Not the cheapest option but it saves call outs from customers. In these cases there is no need for another upstream RCD unless the setup was with the S curve 100mA RCD situated remotely from the CU.




    Again, it depends.


    If it is TT earthing it may need an upfront RCD, whereas if it is TN earthing it may not.


     


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  • 0
    Ian Hildrew:

    Nowadays to reduce the susceptibility to nuisance tripping, good electricians fit every circuit with its own RCBO. Not the cheapest option but it saves call outs from customers. In these cases there is no need for another upstream RCD unless the setup was with the S curve 100mA RCD situated remotely from the CU.




    Again, it depends.


    If it is TT earthing it may need an upfront RCD, whereas if it is TN earthing it may not.


     


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