I hope you had the curtains drawn - if the neighbours saw you doing that they might fear you'd lost it.I've just attempted to do the experiment (well, a safe version thereof!) by attempting to measure the IR of the sole of the (leather-, not rubber-soled) shoes I've been wearing all day (so probably not totally dry). I clamped sheets of metal inside and out, and got an IR of about 16 MΩ at 1000V between them.
You say that, but isn't it a common situation with, say, 3-phase lighting (albeit usually with a 3-pole MCB, not 3 single-pole ones)? As recently discussed, provided that the currents were fairly sine-wave (i.e without excessive harmonics) the single neutral (of same CSA as the Ls) would not be a problem, at least in terms of CCC, would it? Indeed, doesn't essentially the same situation arise with, say, a 1/3-phase cooker fed from a 3P+N supply, if each phase feeds one element - the only real difference (from 3 separate pumps) is that the three elements are 'in the same box', isn't it?
Not really/completely .....
As I understand it, the crucial question EFLI was asking was whether or not there are separate neutrals from each of those 3 new isolators to the 3 pumps (I suspect there are) - is that the case?
That's what I imagined. I'm no authority but, as far as I can see, if you renamed "old isolator" as something like "remote DB", the 3P+N cable between the main DB and that would just be a 'distribution circuit' and everything would be 'as expected', so you would probably not be questioning it?as per attached. the neutral is common back to the board. each phase is on a separate c/b
Yes, but to be honest, contrary to what Mr.Bartlett says, I couldn't make head nor tail of his description.
No, it's not just you. However, his diagram is clear, and corresponds with what I had guessed/assumed. As I've written him, although I'm no expert, it looks fine to me - essentially a 3P+N distribution feed to three single-phase circuits (each with their own neutral
) - no different from what happens in many a DB.EFLI was talking about the final (single-phase) circuits, and noted that all you had told us was that there was 1 x 10A circuit and 2 x 16A ones. With ideal cable routing ('clipped direct') those final circuits could theoretically each have been wired in 1mm² cable.
I'm sure that he can, and probably will, answer for himself, but I think some clues can be seen in:
and
As I've said, for there to be a 'shared neutral' in a 3-phase supply or distribution circuit to the point at which it splits into three single-phase circuits is really just 'as expected'. EFLI presumably also knew this, and therefore was probably struggling to try to work out what 'shared neutral' was concerning you. [Assuming your house has a single-phase supply, the neutral feed to your house will be 'shared' with consumers on the same phase and the other two phases for most of the way back to the substation.]
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