wiring sizes inside CU

[sm_jamieson]

Usually 25mm meter tails go into the CU these days (up to 100A) The norminal sizes of internal connections for a standard split CU, neutral and live connections, etc. seems to be 16mm. For a split CU, you could say only part load is on each neutral connection I suppose. But then the neutral connections narrow down on a reducing pin crimp to perhaps 10mm or less. Then the neutral bars may be connected by a similar small dimension link. For example look at the U-shaped bare copper neutral link (factory fitted) in the photo linked to below.

If the meter tails are 25mm surely the neutral connection from the switch to the neutral bar should be the same, but it is only 16mm. And also the neutral bar itself does not seem all that chunky.

The exception is perhaps the live bus bar, which is a couple of millimetres thick, but are quite large surface area. But the same current is going through the bus bar as the neutral to main switch link.

Is this simply a case of relatively short connections are OK in a reduced dimension ?

Here is a picture of part of my CU (in photobucket):

Just wondering, Simon.

[Bob Minchin]

It is the resistance that is important and on the short link that is minimal.

[Brian Gaff]

I do often wonder however, if a load is switched and there is a short length of reduced conductivity, would the output on anything connected from that point also be more prone to some kind of interference, Ie a high start load momentarily putting a notch into the voltage, or is the crud generally on mains supplies now so bad that nobody should notice. I notice for example that I can hear the thud when a 3KW fan heater cuts in on the same ring as my stereo is on. Not loud, but you can hear it. Brian

[Bob Minchin]

That is highly unlikely to be mains bourne and more like RFI transients at the switch and direct detection of same in the front end of your stereo.

[tabbypurr]

What xsa are those conductors? The biggest loads only flow through part of the bar, not all.

NT

[Cursitor Doom]

If you're talking about the skin effect, it's really not a factor at 50Hz.

[tabbypurr]

I didn't mention the skin effect.

NT

[Cursitor Doom]

So what, then? Current crowding? What's the phenomenon you're referring to?

[Roger Hayter]

He probably means part of the bar longitudinally rather than transversely.