Hi folks, Firstly I have just shelled out £45 for some GS38 test leads. A pair of leads; 1.2m long! £45! I reck the H&S police should go and duck off! Tvvats! Anyhoooo... Am a bit confused of dis times. I thought that for a typical domestic TN system the dis time is 0.4 if less than 32A cct. However, just been looking through a couple of PIR's from other sparx and they have listed lighting as 5s and power ccts as 0.4s.. Is that correct? Regs seem to say otherwise.. Although imho it seems more sensible to have a higher amp cct with a quicker dis time.. Anyone.... please... Thanx
Hi barabari In 17th edition for TN earth its 0.4s all circuits (0.2s for TT). The 5s disconnection time no longer applies; it is a remnant of 16th and earlier regs. Regards
3.5.2 Disconnection times - TN circuits A disconnection time of not more than than 0.4 s is required for final circuits with a rating (In) not exceeding 32A A disconnection time of not more than 5 s is required for -final circuits exceeding 32a -distribution circuits..
Yeah spark and a 1/2, I concur! Sooo, a dedicated 9.5kW shower cct draws a possible/hypothetical 41A. This is permitted to take up to 5 seconds to disconnect. That sounds bad to me - surely with such a high load then ADS should be quicker. That is what it says in the regs though. Have dis times been altered from those found in 16th ed in line with 17th requirements for full RCD protection....?? ie Have the dis times been changed to reflect the extra protection offered by a RCD.. Ta
Might be me being thick but surely if a cct is protected by a 30mA RCD (which the majority will be since 17th ed) then the disconnection time is not 0.4 seconds but 40mS at 1xIn which is in fact 0.04 seconds??? So as far as a 40A shower, obviously in a room containing a bath or shower, then the disconnectin time is 0.04 secs not 5??
RCDs should open in 200mS with a LEAKAGE current flowing equivalent to 100% of the rated trip current e.g. 30mA (OSG 11.4 ii) MCBs - Circuits not exceeding 32A : - BS7671 Table 41.1 TT 0.2S and TN 0.4S Circuits exceeding 32A - TN - 5s, TT - 1s (BS7671 411.3.2.3 & 4) This is fun isn't it!
Thanks all for responses. One thing tho; Lokkers the shower could be a cooker or something with similar consumption. So under 16th would not have necessarily required RCD. Again thanks good peeps..
Part p has nothing to do with the amount of duff info, the duff info comes only from those who don't know the correct info. Prior to part P i suspect there were just as many of those.