R
radiohead
I assume you mean TN....not TT? Any rating of type D would have a 100% chance of being compliant in a correctly designed TT.I would say a 6A D type MCB or RCBO would have a 50% (approx) chance of being non compliant in a domestic situation as the Zs would have to be max 1.46Ω (TT).
I would say a 32A D type MCB or RCBO would have a 98% (approx) chance of being non compliant in a domestic situation as max Zs is 0.28Ω (TT).
My aspergery brain starts overheating when the word 'likely' is used as it is so subjective! It doesn't mean anything in this scenario. Even my approximations above are ridiculous as they are only ever so slightly less subjective.
It's a bit like that old 80's film 'war games' when the computer tries to find a winner in nuclear war and breaks down due to infinite 'no win' outcomes.
I will now stop drinking coffee.
I agree on a TN in many existing situations a device exceeding 6a may be non compliant, but in new additions, alterations and new installations in domestics any rating of a type D mcb is probably 100% likely to comply because virtually all circuits will have RCD protection, and an RCD is a permitted means of earth fault protection. RCD's are not only for additional protection, something that is often overlooked.