The regulations state 300ms for BS61008-1/9-1.I looked for tripping times at 30 mA and it seems this depends on the BS number of the RCD
Table 3A, Page 318.I can't find anything in my copy of BS7671:2008 giving a time for disconnection at 30 mA only at 5 x 30 mA.
It is presumably the 0.4s usual required disconnection time which does not apply to RCDs for some reason.don't know where 400 mS comes from?