I'd call that a short.
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6 years ago
Another electricity supply question
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6 years ago
"Limited experience" would be a better.
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6 years ago
well since a dead zero ohm short is a physical impossibility, one has to say he is right.
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6 years ago
It's zero for BS7671 regs and calculations.
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6 years ago
Then they are meaningless
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6 years ago
So you think they conduct 1000s of amps during failure. They don't.
NT
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6 years ago
Ah. So you wish to define how much current flows during a short circuit?
This should be intersting...
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6 years ago
Even on a PME supply you only need to extend the equipotential zone to the shop CU if there is something that needs bonding. I was suggesting that that shop may have it's own extraneous conductive parts.
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6 years ago
I'm pretty sure they conduct 100s of amps, they certainly arc, and they trip MCBs in a fraction of a second. At least they do in this house.
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6 years ago
No, you just use the resistance of the existing supply and wiring depending where you introduce the theoretical zero ohm short.
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6 years ago
- you keep snipping that. Weird.
A lamp arcover is not a short circuit.
NT
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6 years ago
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6 years ago
Who said they arc over? What usually happens here is the MCB just trips.
But I asked for your definition of a short circuit against an overload. Since you seem to know the difference.
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6 years ago
Indeed, and for a normal B6 MCB any current over 30A should do that. (changing to a C6 (60A magnetic trip threshold) will eliminate some (but not necessarily all) filament lamp trips IME.
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6 years ago
Not when you calculate (or measure) the Prospective Fault Current or Prospective Short Circuit Current, values of which will be dictated by the fixed wiring and the nature of the supply and earthing system.
You can't meaningfully quantify the resistance of the fault itself since at design time its unknown.
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6 years ago
Pretty much every lamp expert that has written about the issue.
Of course I do. You appear not to know what you're talking about again.
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6 years ago
They may or may not. Depending on the lamp design.
So please give your definitions. A simple enough thing for you to do surely? Except you've opened mouth before engaging brain again.
Rather obviously any short circuit is an overload. But not every overload is a short circuit.
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6 years ago
you're hovering right on the edge of the plonk filter.
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6 years ago
Right. Photos here :
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Thanks!
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6 years ago
Oh, nice job. ta.
(I think your description probably wants a "(far left)" where it currently has a "(far right)" ;-)
That looks like its TN, now the next question is TN-S or TN-C-S - hard to tell from just the picture. If you were to take out those two screws on the rectangular faceplate just under the main fuse, and have a peek in there, that would probably tell you.
For example:
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Shows what could be a TN-C-S cutout, but the link between the neutral and earth blocks on the right is missing, and a discrete earth connection from the armour of the split concentric cable is connected to the bottom of the earthing block on the far right.
Compare with:
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That has the link in place to join the earth terminal to the incoming neutral at the cutout.
I would guess yours will be like the former (i.e. TN-S)
Adam may be able to spot more from the photos.