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Standard GU10's are brilliant at it!


I don't doubt it, but I count them as incandescents, and don't use them. Anything with a filament is pretty likely to have (very brief) very-high-current 'death throes', often enough to trip and MCB!Standard GU10's are brilliant at it!
True.Well be don't know the OP's choice of illumination.
... and be happy with the fact that switching off one of the MCBs could then leave bits of the corresponding circuit potentially 'live'?But given the amount of spare B6's in that board, I would split them.
As I said, what is colloquially called 'borrowed neutral' can, in practice, be a 'borrowed line' (either will result in trips if the two circuits are on different RCDs). These situations usually exist when there is 2-way light switching and either neutral or line for one of the lamps is taken from the other circuit, usually because of the convenient proximity of a suitable cable.How would the other become live ? What conditions would have to exist ?
If there is a 'borrowed line' and you switch off just one of the MCBs (e.g. to do work on the corresponding circuit), some parts of the circuit will still be getting 230V via the other MCB.And if you have 2 lighting mcbs on the same rcd, why is there a shock risk ?
Not only that. Even without disconnecting anything, there could be a live conductor at one of the switches on the 'switched off' circuit - which would be a hazard (L-E shock) whether or not the neutral were disconnected.Yes ok. If you went disconnecting the neutrals you could get a shock.
As above, isolating the neutral to the circuit in question wouldn't necessarily help. If both circuits were on the same RCD (as they would have to be) and you 'flipped the RCD' that would obviously make things safe - since the L feed to both circuits would thereby have been disconnected. In passing, as far as the regs are concerned, isolation of neutral is not necessary in TN installations.I thought the guidance was that you should isolate both conductors before working on the circuit? (Flip the rcd)
There's a splendid article with diagrams in the Wiki explaining the problem.And if you have 2 lighting mcbs on the same rcd, why is there a shock risk ?
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