Its very interesting this issue of loss. I have a very beefy armoured cable
connected to a 13 amp spur in the house and used to feed a couple of sheds
and a garage 100 foot away, for normal stuff its fine, even domestic power
tools but add a fan heater and you can see the lights dim as it turns on.
Obviously not a serious issue in the main for such things, but far worse
than the conductor diameter might have indicated.
Nowhere near the 13 amp fuse though of course if you were daft enough to
put lots of high current devices on the end the fuse in the spur would blow
telling you you really should have it wired through a proper separate
breaker on the CU!. This was a while ago when I could see. Since there is
only one shed left, when I reconnect the cable I'm not going to replace the
current system!
Brian
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"John Rumm" wrote in message
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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.
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Cheers,
John.
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