I have tried everything (inc password) to join Sparky Heaven, without success. Would it be possible for someone to send me any C&G 2391 past papers. I sit mine in July, I'm really desperate
1. for a T-N-S system, calculate the maximum permisable Zs of a 30mA rcd.. ( no other info given.. )
i worked it out ( after an epiphany at 1:50.. good job I sat there... ) that it was 50/30mA = 1666 ohms... this sounds high for me but is ok to the regs for dry locations on TT systems..
can't find the formula for T-N-S systems though.
Your right om the 1666 ohms but some say `but no more than 200 ohms`
Whether its a T.T, TNC-S or a TNS the max Zs is the same, so for C&G to mention TNS system their just trying to be foxy!!!
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