I am away from the regs book (but who needs it anyhow Lucien!😀) but I think the minimum size for the Main earth conductor for a TT is 2.5mm or perhaps 4mm as opposed to the minimum for a TNC-S being 16mm for new builds.
It is very likely that a TNC-S will have a greater PFC ( compared to a TT) as the Ze will be <0.35Ω but a TT can have a very low Ra (sometimes very low... as Trev would have confirmed ... RIP :sad_smile🙂 so its PFC could be as high as a TNC-S but it may have a main earth conductor size of only 2.5mm?
Why the difference in minimum sizes?
I'm afraid I'm away from home at the moment and would have liked to have read through some of my books to gauge an answer before posting.
Continue reading...
It is very likely that a TNC-S will have a greater PFC ( compared to a TT) as the Ze will be <0.35Ω but a TT can have a very low Ra (sometimes very low... as Trev would have confirmed ... RIP :sad_smile🙂 so its PFC could be as high as a TNC-S but it may have a main earth conductor size of only 2.5mm?
Why the difference in minimum sizes?
I'm afraid I'm away from home at the moment and would have liked to have read through some of my books to gauge an answer before posting.
Continue reading...
