I am also slightly confused as to why the 5x RCD test has not been dropped, what was the point of doing it all this time?
The BSEN product standard published trip times for 1/2, x1 and x5, and I'd assume the original idea was to thoroughly make sure the device was still in spec.
I think a few things might have fed the change.
1 - sparks weren't always understanding the slightly complicated requirements of the test. The number of times I've said "that's passed at under 40ms at x1, you don't need to do a x5, it won't be slower!"
2 - Since type A's have been around, plenty were incorrectly putting their new shiny tester onto type A, and expecting the device to trip within type AC times. The BSEN product standard requires 350ma to trip a 30ma type A within 40ms and the machines don't deliver enough current, many delivering 210ma (30 x 5 x 1.4).
There never has been a pass result for a type A test published in BS7671, so for the test machine to say "fail" is misleading and has fed much confusion. Device manufacturers have complained that it was a perfect storm.
3 - the amount of DC leakage commonly about in the average house, especially on a split load / dual RCD board increases the chances of type AC not quite managing 40ms @ x5 under load when it still in fact works as well as it's ever going to. Replacing it like for like would not improve anything, and the unit is not faulty, it's the environment that is causing the problem. Conversely it would usually manage under 300ms at X1, if it isn't stuck though lack of testing at all that is.
4 - it was frankly rather tedious to check 1/2 twice, x1 twice, x5 twice especially in commercial/industrial premises during the day! My Metrel does a ramp test too on the Auto setting.
I've yet to read it all properly, but one video from the IET implies that checking both 0 degrees and 180 degrees is not required now. So it might be a single x1 test. We'll see in due course!
