Regulation stating a type AC RCD can not be upstream from a type A RCD

There is a great deal of confusion about RCD types and I'm afraid the regs book provides little assistance. However:

There is no regulation of how many protective devices may be present on any circuit. This means that you may have 6 levels of fusing, but as long as one of them matches the circuit parameters (cable, load etc) then it is fine, eg a ring circuit with plug fuses and another inside an appliance or extension cable.. The same applies to other circuit protections such as RCDs, typically a type S and something quick. If there are two RCDs in series, as long as one of them is rated to provide the circuit protection required, then there is no problem, although both may trip but at least one will. This means that a charge point with built in type A or B or F or something new, may be fed from anywhere, whether it has another type which may not provide protection needed by the load, in this case the EV.  Remember you are only providing additional protection for the EV, and it is only needed when the vehicle is charging. At other times a type AC will provide additional protection because there is no DC on the circuit.

This problem has partly come about because electric vehicles use the Earth conductor for signalling with DC, and it looks as though this set off the whole thing with the IEC, and the exact definition of DC is open-ended, as shown in Table 55.3. You should note that there is no figure for the amplitude of these pseudo DC signals, but there seems to be an assumption it is more than 6mA, and secondly that this will prevent tripping of type AC, and increasingly other types. I have done a lot of testing on this and I have a type AC here which is unaffected by 100 mA of pure DC (Real DC), and works at a similar level with the other waveforms. The problem is that some others do not, and so we don't know, and the manufacturing standards are not very clear either, patrticularly when there is a large static AC current and an additional protection type leakage which should cause a trip. Note we always test RCDs completely unloaded.

I hope that lot is helpful, NAPIT is not, its book is in many places inadequate, it should not be used as an installation standard, and any competent inspector does not need it anyway.

There is a great deal of confusion about RCD types and I'm afraid the regs book provides little assistance. However:

There is no regulation of how many protective devices may be present on any circuit. This means that you may have 6 levels of fusing, but as long as one of them matches the circuit parameters (cable, load etc) then it is fine, eg a ring circuit with plug fuses and another inside an appliance or extension cable.. The same applies to other circuit protections such as RCDs, typically a type S and something quick. If there are two RCDs in series, as long as one of them is rated to provide the circuit protection required, then there is no problem, although both may trip but at least one will. This means that a charge point with built in type A or B or F or something new, may be fed from anywhere, whether it has another type which may not provide protection needed by the load, in this case the EV.  Remember you are only providing additional protection for the EV, and it is only needed when the vehicle is charging. At other times a type AC will provide additional protection because there is no DC on the circuit.

This problem has partly come about because electric vehicles use the Earth conductor for signalling with DC, and it looks as though this set off the whole thing with the IEC, and the exact definition of DC is open-ended, as shown in Table 55.3. You should note that there is no figure for the amplitude of these pseudo DC signals, but there seems to be an assumption it is more than 6mA, and secondly that this will prevent tripping of type AC, and increasingly other types. I have done a lot of testing on this and I have a type AC here which is unaffected by 100 mA of pure DC (Real DC), and works at a similar level with the other waveforms. The problem is that some others do not, and so we don't know, and the manufacturing standards are not very clear either, patrticularly when there is a large static AC current and an additional protection type leakage which should cause a trip. Note we always test RCDs completely unloaded.

I hope that lot is helpful, NAPIT is not, its book is in many places inadequate, it should not be used as an installation standard, and any competent inspector does not need it anyway.