Do you mean RCBOs (most, but not all, have 'flying earth leads')? There might also be some RCDs which do have such tails, but I've personally never seen one.Just wondered.
Interesting - as I said, for what it's worth, I've never seen one. However, as far as I can see the argument for having a functional earth is exactly the same for RCDs as for RCBOs, but it was only when RCBOs appeared that we (at least, I) started seeing them.Well funny you should say, because the pretty much the only RCDs I can find with a functional earth is the brand for my CU: .... Hence why I asked the question.
Another often-made point is that, without a separate earth connection, an RCBO cannot detect an earth fault if the neutral becomes disconnected. This is true, but in reality it is not an issue worthy of consideration.
Losing the neutral connection is a rare event in itself, especially in the TN-C and TN-C-S systems that are almost invariably used today. The probability of losing the neutral and having an earth fault at the same time, a double fault condition, is vanishingly small – certainly so small that there is no reason to take it into account when specifying protection devices.
Thanks. That sounds remarkably similar to what I wrote above.Eaton's reasoning is ....
Indeed. That's what I've said, more than once. I can't see that there can be any true logic in it.I don’t really understand the logic of putting them on RCBOs and not on RCDs. Surely the probability/protection argument is the same ....
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