oh absolutely - but if you ask people to mark their own homework, when money depends on something, it can be remarkable what passes - its the argument for local authority building control inspections, rather than self certification. Equally, independent inspection is expensive and the real cost of failure may not be so great to warrant it. But lets not pretend that folk are always perfect.

Mike.

My apologies! This demonstrates the perils of cut and paste. I have amended the link in my earlier posting.

I entirely agree with your further point.

I worked on a site two years ago that had these AFDDs spec'd. They were, in effect, in a split load, double RCD board. Actually, they were in a double deck DB, with RCBOS (only 2 or 3) in the top din rail, with two rcds, and 4 or 6 AFDDs in the bottom din rail (2 or 3 AFDDs per RCD)

I took one of these DBs with me when the site was finished (no I didnt steal it!), and I've used it in my own house. No real reason to use it, but it was free, so why not. No nuisance tripping yet.