1667 question

[leespeed]

i thought no matter what the reading of a circuit protected by an rcd or rcbo still had to be within the maximum readings of the regs
just incase the rcd or rcbo fails / just a thought .additional protection only........?

 

[telectrix]

if it's a TN system, yes, but a TT system will very rarely give you Zs values to comply, so you then rely on the RCD(s) to meet disconnection times.

bear in mind that the 1667 value applies only to 30mA RCDs. the values for 100mA and 300mA are 500ohms and 167 ohms respectively.