On 15/09/2018 13:54, Roger Hayter wrote:
Cursitor Doom wrote:

On Sat, 15 Sep 2018 20:42:02 +1000, FMurtz wrote:

Tim Streater wrote:

Does the 1.5mm refer to the overall diameter of the flex, the diameter
of each core including insulation, or the diameter of each core
excluding insulation.

Every one knows what he is referring to except maybe you.

I'm more of an old imperial measurement type (AWG/SWG etc) but believe
that 1.5mm is *way* too thin to make an extension lead out of (unless you
just want to make up something specifically for a lightly loaded lighting
application.

In an ideal world you'd think so, wouldn't you? But in practice I had a
lot of searching to do to find someone who'd sell me a made up extension
lead on a reel 25m long and 2.5mm^2 flex. Nearly all the popular
mass-market ones are 1.5mm flex. Still rated at 13A unwound (as the
electricians will tell you) but a significant power loss for 2.2kW power
tools.


I can see no more than a 3.5% voltage drop on a 25mm length of 1.5mm 3
core flex happening when using a 2.2kW load.

That will not be a problem for most power tools.

Was this for some tool with an inrush current?

Or to put it another way, my voltage is a nice 252V (and a PSC of 12kA
and a Ze of 0.01 ohms) but I often work on places with much lower
voltages and higher Ze readings.

Now if you have a Ze closing in on .3 ohms [1] I can see the extension
lead making a bigger difference especially if plugged in at the mid
point of a large ring or the end of a radial.

[1] I have not seen much higher that that for a long time even on a TNS
supply.

I have seen it a lot on building site with 110V transformers and long
leads. The performance of chop/mitre saws seems to suffer the most.

--
Adam