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

Just thinking aloud - say we had something with an internal d.c. supply, not galvanically isolated from the mains ('cos it's cheaper) that could under certain fault conditions send a limited current (a few 10s of mA perhaps) to PE - I've got in mind something like an LED bulkhead with an LED strip stuck to an Earthed steel dish.

Do I have in mind (much simplified) something like:

That of itself wouldn't be hazardous, but it seems like it could disable an AC type RCD, so loosing additional protection not just from that circuit but any other circuits that rely on the same RCD (as in split load CUs), and the first fault could persist indefinitely. It'd still need a 2nd fault for danger, but where we have additional protection we'd expect something rather better than just the old-fashioned two-faults to danger, which we're not really getting any more.

   - Andy.

 Primary simple, reliable, protection is afforded by good solid earthing and bonding in association with overcurrent protective devices. (Excepting TT installations).

Z.

AJJewsbury said:

Just thinking aloud - say we had something with an internal d.c. supply, not galvanically isolated from the mains ('cos it's cheaper)

If you think about it, even in galvanically-isolated power supplies, all you've drawn is what's up-front in a switched-mode power supply - rectifier straight onto mains, and a relatively large reservoir capacitor. MIcrowave oven HT supply may have half-wave or full-wave rectification of mains up-front, etc.

AJJewsbury said:

Just thinking aloud - say we had something with an internal d.c. supply, not galvanically isolated from the mains ('cos it's cheaper)

If you think about it, even in galvanically-isolated power supplies, all you've drawn is what's up-front in a switched-mode power supply - rectifier straight onto mains, and a relatively large reservoir capacitor. MIcrowave oven HT supply may have half-wave or full-wave rectification of mains up-front, etc.