Explain why RCDs fitted into extension leads or incorporated into plugs are forbidden

Under what conditions is it sensible to ban or remove RCDs inline with plugs or extension leads ?

Perhaps add:

3) Where (a single layer of) additional protection is needed and you want it done in the best (least unreliable) way available.

From a H&S perspective the can be a danger of having too obvious "backup" protection - i.e. people tend to start to rely on it. I remember a H&S course years ago where the presenter said he had 5 lights in one of his rooms - one day there was a pop and the room was left in darkness. What happened he asked? One lamp blew and the MCB tripped suggested most of us with any electrical knowledge. No he said - MCB was still on. A few puzzled expressions. He explained that a few ears earlier all five lamp where working, one blew, but he didn't bother replacing it as there was still plenty of light from the remaining 4, Later another blew, but three was still more than enough light and it was a lot of effort to get the step ladder out, when it got to two left he started thinking that he should do something about it but didn't quite get around to it, when there was only one left it moved up the metal priority list as it were, but as there was still enough light for what was needed he still hadn't quite got around to replacing any of the lamps before the 5th eventually blew.

I can see an (avoidable) risk that if someone had a plug-in RCD to use they won't bother checking that the wall socket is RCD protected.

Secondly, are we that sure there will always be an RCD upfront  if it is not a TT building ? The evolution of the regs and the time delay between changes and universal implementation is much longer than some authors on here imagine.

This is a workplace policy - so presumably the authors are aware of the situation on their particular site, and the procedures they expect their staff (both electrical and 'ordinary') to follow. They may have all sockets RCD protected or have some means of identifying which are.

If I were in that situation - say writing a procedure for use of electrical equipment outdoors, I think I'd be happier saying something like "only plug into one of the sockets marked 'for equipment outdoors'" knowing that the RCD behind that was reasonably well protected and subject to regular checks & tests, rather than allowing the option to plug into any socket you like but use a plug-in RCD that's might have been collecting dusk in the back of a filing cabinet for 10 years or been bouncing around in the back of someone's van or was left out in the rain yesterday.

Certainly, personally, I'd be more than happy to have a plug-in RCD in addition to RCD protection in the installation, but I'm the kind that had enough shocks during my miss-spent youth to be pretty respectful of electrical dangers. But most people will just to the absolute minimum the procedures demand of them - often not even that if they're seen as complicated or time consuming - so simple and reliable perhaps trumps the ideal.

    - Andy.

Under what conditions is it sensible to ban or remove RCDs inline with plugs or extension leads ?

Perhaps add:

3) Where (a single layer of) additional protection is needed and you want it done in the best (least unreliable) way available.

From a H&S perspective the can be a danger of having too obvious "backup" protection - i.e. people tend to start to rely on it. I remember a H&S course years ago where the presenter said he had 5 lights in one of his rooms - one day there was a pop and the room was left in darkness. What happened he asked? One lamp blew and the MCB tripped suggested most of us with any electrical knowledge. No he said - MCB was still on. A few puzzled expressions. He explained that a few ears earlier all five lamp where working, one blew, but he didn't bother replacing it as there was still plenty of light from the remaining 4, Later another blew, but three was still more than enough light and it was a lot of effort to get the step ladder out, when it got to two left he started thinking that he should do something about it but didn't quite get around to it, when there was only one left it moved up the metal priority list as it were, but as there was still enough light for what was needed he still hadn't quite got around to replacing any of the lamps before the 5th eventually blew.

I can see an (avoidable) risk that if someone had a plug-in RCD to use they won't bother checking that the wall socket is RCD protected.

Secondly, are we that sure there will always be an RCD upfront  if it is not a TT building ? The evolution of the regs and the time delay between changes and universal implementation is much longer than some authors on here imagine.

This is a workplace policy - so presumably the authors are aware of the situation on their particular site, and the procedures they expect their staff (both electrical and 'ordinary') to follow. They may have all sockets RCD protected or have some means of identifying which are.

If I were in that situation - say writing a procedure for use of electrical equipment outdoors, I think I'd be happier saying something like "only plug into one of the sockets marked 'for equipment outdoors'" knowing that the RCD behind that was reasonably well protected and subject to regular checks & tests, rather than allowing the option to plug into any socket you like but use a plug-in RCD that's might have been collecting dusk in the back of a filing cabinet for 10 years or been bouncing around in the back of someone's van or was left out in the rain yesterday.

Certainly, personally, I'd be more than happy to have a plug-in RCD in addition to RCD protection in the installation, but I'm the kind that had enough shocks during my miss-spent youth to be pretty respectful of electrical dangers. But most people will just to the absolute minimum the procedures demand of them - often not even that if they're seen as complicated or time consuming - so simple and reliable perhaps trumps the ideal.

    - Andy.