My house had a new consumer unit fitted in 2005 it's partly fitted with RCBOs and partly with MCBs it was installed by the DNO who are SSE in this area bearing in mind the year it was installed are the rcd fitted likely to be electronic type or plain electromechanical ones I'm asking out of curiosity because if ever there's a fault in my workshop ( for this read that I make a mistake or an error when experimenting) usually the house RCD trips despite me having an electronic plug in one on my test bench supply which I think should fire first ide really appreciate your wise words on this thanks x Kelly
If you have 2 RCDs in series unless you have time delay on one then you will not get selectivity (the new name for discrimination). I am assuming you effectively have 2 30mA RCDs in series so you will not have any time delay?
Whilst you may have different sensitivities when you ramp test them your experiment gone wrong may have been a lot more than 30mA fault current. If so it is a complete toss up which one goes first. Unless the have different levels of DC immunity say a Type AC and a Type A and there is a DC component to your fault current. A low level of DC may lock up a Type AC but not a Type A. A lot of manufacturers have stopped shipping Type ACs in favour of Type As as these are the minimum standard in some countries.
I managed to trip my BS 4293 RCD in my workshop when trying to get my AFDD on test by pulling the neutral out of a terminal block to create an arc with a fan heater as a load. Lots of sparking which did not trip the AFDD but my ancient 30mA RCD did not like it!
If you have 2 RCDs in series unless you have time delay on one then you will not get selectivity (the new name for discrimination). I am assuming you effectively have 2 30mA RCDs in series so you will not have any time delay?
Whilst you may have different sensitivities when you ramp test them your experiment gone wrong may have been a lot more than 30mA fault current. If so it is a complete toss up which one goes first. Unless the have different levels of DC immunity say a Type AC and a Type A and there is a DC component to your fault current. A low level of DC may lock up a Type AC but not a Type A. A lot of manufacturers have stopped shipping Type ACs in favour of Type As as these are the minimum standard in some countries.
I managed to trip my BS 4293 RCD in my workshop when trying to get my AFDD on test by pulling the neutral out of a terminal block to create an arc with a fan heater as a load. Lots of sparking which did not trip the AFDD but my ancient 30mA RCD did not like it!
