Type A rcd . EICR coding ? etc

Those are reasonable points Nathaniel, but there are wider issues. First, is what happens to present installations? Type AC is perfectly safe in 99% of cases, yet I can see many code C1s generated if the type is simply removed from the regulations. If manufacturers are changing the type anyway (and this may be because type A is widely used elsewhere, and I'm not sure that most are not of this type already although marked as AC) because it is not a requirement not to respond to unipolar (DC) faults. MFTs give one a setting to change the fault phase from positive cycle first to negative first, which often changes the trip time. Why this change happens is not very clear, and maybe a type AC phenomenon, but adding a new test to give a rectified waveform of either polarity is not difficult. In fact, I will try this next time I have my RCD testing jig out as the result would be interesting, and I will report back. There is very little electronics that uses half-wave rectification, even low power items, and LED light bulbs seem to have full-wave rectifiers at the few watts level. There is also a case that Earth faults inside electronic items are very unlikely, because of the insulation and creep distance required from mains components, and failure of the EMC filter capacitors can never be DC (rectified AC or whatever). Whilst a rectified type of fault current cannot be totally discounted, it does seem very unlikely. Changing every type AC for a type A, as suddenly being dangerous is clearly completely unacceptable to customers, as in many cases we would end up with many more CU changes for unreasonable reasons, for example, a type-tested type A is not available for the existing CU.

Those are reasonable points Nathaniel, but there are wider issues. First, is what happens to present installations? Type AC is perfectly safe in 99% of cases, yet I can see many code C1s generated if the type is simply removed from the regulations. If manufacturers are changing the type anyway (and this may be because type A is widely used elsewhere, and I'm not sure that most are not of this type already although marked as AC) because it is not a requirement not to respond to unipolar (DC) faults. MFTs give one a setting to change the fault phase from positive cycle first to negative first, which often changes the trip time. Why this change happens is not very clear, and maybe a type AC phenomenon, but adding a new test to give a rectified waveform of either polarity is not difficult. In fact, I will try this next time I have my RCD testing jig out as the result would be interesting, and I will report back. There is very little electronics that uses half-wave rectification, even low power items, and LED light bulbs seem to have full-wave rectifiers at the few watts level. There is also a case that Earth faults inside electronic items are very unlikely, because of the insulation and creep distance required from mains components, and failure of the EMC filter capacitors can never be DC (rectified AC or whatever). Whilst a rectified type of fault current cannot be totally discounted, it does seem very unlikely. Changing every type AC for a type A, as suddenly being dangerous is clearly completely unacceptable to customers, as in many cases we would end up with many more CU changes for unreasonable reasons, for example, a type-tested type A is not available for the existing CU.