On 15/03/2012 13:42, Fred wrote:
Hi,

About ten years ago I bought an extension lead from Wickes. Not
knowing any better at the time, I bought a long one, thinking that a
long one could be used when long or short lengths were required,
whereas a short one could only be used for short lengths.

Then I came and read here and I learnt that long leads had
disadvantages. I can't remember now whether this was because of
voltage drop or fault currents, or may be both. Can someone remind me?

The answer is both, and also "heat"...

The longer the lead then the more voltage drop. May not be a huge
problem for many tools (power tools run a bit slower and with a bit less
oomph), but some kit may get upset (things with induction motors that
may stall on startup, or run but attempt to compensate for lack of volts
by drawing more current, and then overheating)

The second issue is fault current, or to be more accurate lack of it.
Long leads will have a higher earth loop impedance, and also a lower
prospective short circuit current. So when something goes pair shaped
the fuse in the lead takes longer to operate, or in the worst case, does
not operate at all in a sensible time. Making sure its fed from a RCD
protected socket is obviously a "good thing" (tm).

Lastly, heat. Long leads can only take a small proportion of their full
load when wound. Hence for big loads at moderate distances, you may find
yourself having to unwind a rats nest of cable to use it safely.

Anyway, some of my tools have started switching on and off
intermittently when plugged into the lead, and I can only assume that
over the years the contacts in the extension socket have been worn and
are not making a good connection to the plug.

Either that, or the flex has broken and gone intermittent at the ends
where it bends a lot.

The socket terminals might allow a bit of cleaning and bending to get a
better grip. The flex can have the first and last metre cut off and be
re-terminated to get rid of the dodgy bits.

So it is time to buy a new lead or leads. I seem to remember reading
that 1.5mm^2 cores could only be used safely up to 15m and 2.5mm^2
cores (in a caravan power lead) could be used up to 25m. Is there any
advantage to buying a short "caravan hook-up" cable to use for lengths
under 25m?

Depends on the loads you need to run partly. If you are doing big ones
at moderate distance, or ones for which voltage drop is going to be a
problem, then it may be worth it.

Otherwise I'm thinking I could use the cable from the Wickes lead, or
possibly use arctic flex as an improvement, to make some short leads.



--
Cheers,

John.

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