On 15/09/2018 14:34, Cursitor Doom wrote:
On Sat, 15 Sep 2018 13:54:12 +0100, Roger Hayter wrote:

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.

Good Lord!! For once I'm lost for words. :-/

So 25m[1] of 1.25mm^2 flex, will have about 24.20 mOhms/m round trip
(i.e. L+N).

So that's about 0.61 ohms for the whole lead. A 2.2kW tool suggests
about 9.6A of load, so that would give a dissipation of about 56W... not
massive, but enough to get it reasonably hot. At a full 13A load that
gets to 100W.

[1] I have some 50m extension leads as well, in an enclosed spool, so
200W of dissipation on that might be more of a problem if used coiled.


--
Cheers,

John.

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