extension leads

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?
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.
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?
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.
TIA
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Some of those older sockets were amenable to being taken apart and resprung to make them work again. I found those four way ones tended to have a problem where they connected to the bus bars. its all by pressure and over the years things relax and get tarnished. Brian
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On Thu, 15 Mar 2012 13:51:12 -0000, "Brian Gaff"

This is 2-way and I did wonder about giving the brass a little squeeze with some pliers but I wasn't sure if I would be fighting a losing battle.
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Fred wrote:

Replace the sockets instead of buying new leads if they are structurally sound.
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wrote:

This was a reel with integral sockets. I doubt I could buy replacement sockets top fit in the reel, but yes, I had thought of using the cable to attach to a new trailing socket. Thanks.
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wrote:

Biggest problem with modern long leads is that if you use much power you have to unwind the whole lot to prevent overheating. If you use thicker cable you add to the size and weight. Intermittently used power tools are probably not a problem but our wallpaper steamer is.
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On 15/03/2012 15:27, Hugh - Was Invisible wrote:

Or in the case of our local church fete a pair of 3kW kettles on a mostly rolled up mad hot extension lead plugged into the wall. They did it last year as well completely melting the inside of the reel. *SCARY*
I am inclined to the view now that they should include a thermal cutout! The clear warning on the reel has little or no effect on most folk :(
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On 15/03/2012 15:36, Martin Brown wrote:

The modern 50m JoJo ones do include the cutout these days... presumable for this sort of reason.
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John Rumm wrote:

The extension lead Geoff gave me has a thermal cut out and it has operated twice.
Once when a pillock plugged in a 2kW heater without unwinding it (he was told not to) and then again when another pillock decided to charge up two cherry pickers without unwinding it (without asking to use it).
I was suprised at how long it took to reset the trip/cool down even after I had unwound the lead.
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On 15/03/2012 18:07, ARWadsworth wrote:

Had a look, but would want a 10m one or maybe 20m and they don't seem to have thermal protect at least according to the summary at Farnell.

Still preferable to ending up with a molten mess of plastic and cable all gummed up together. I was amazed the previous one didn't catch fire!
I also reckon they should be aggressively limited to no more than 20A for 10s to avoid other obvious stupidity like 2 kettles which is an overload condition on a 13A socket even with the cable unwound.
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On 16/03/2012 11:33, Martin Brown wrote:

Although less common on the shorter leads, there are some by the looks of it:
http://cpc.farnell.com/jojo/706724/cbl-reel-4-skts-c-out-13a-10m/dp/PL08818

Two 3kW kettles probably would take out the plug fuse in under a minute.
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On Fri, 16 Mar 2012 14:02:12 +0000, John Rumm wrote:

Thats not quite a 100% overload. I think the average BS<whatever> plug top fuse would last longer than that(*). Wether the plug top could take the heat generated is another matter...
(*) Wonkypeida says for a 13A fuse 1-400s @ 30A (6.9kW). My experience of urns and kettles on the same 13A plugtop is that it take quite a number of minutes for the fuse to blow and the plug top melts as well.
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On Mar 16, 5:17pm, "Dave Liquorice"

A strictly 3kW kettle, 3000W, is 12.5A at 240V. I think most are quoted as a range such as 2960-3180W etc.
Coopers BS1362... - 1.6*In (20.8A) MIN of 30min - 5000W - 1.9*In (24.7A) MAX of 30min - 6000W.
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On Mar 16, 7:00pm, "Dave Liquorice"

The variation probably covers resistance variation as well - it is only a kettle.
For example of the four otherwise identical 700W heaters I have had, the element wattage measured by plug in energy meter vary from 707W to 823W. The precise figure may be wrong, but as a resistive load there is clearly quite a variation.
I think I remember a 600W kettle once... it might be boiled by now, must find it!
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On Fri, 16 Mar 2012 13:15:53 -0700 (PDT), js.b1 wrote:

I've got a 100W kettle use it quite a bit, takes about 20 mins to boil a large mug full of water. Runs off 12v mind and the lead does get warm...
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wrote:

Are these oil filled radiators by any chance? I was looking for something to stop the garage freezing over winter and I saw some oil filled rads that were rated 700W and I though t it was a strange number. I thought the manufacturers would have aimed for 300W more to make a kiloWatt. I thought 1000W sound better for marketing purposes!
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Assuming it's not the first time this has been done, the fuse could well be rather weaker than spec.
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On 16/03/2012 17:17, Dave Liquorice wrote:

I was going from the graph in BS1362:
http://wiki.diyfaq.org.uk/images/d/da/BS1362FusingTime.png
However to be fair that is the lower limit of the range of possible values, so it may well last longer depending on the fuse.
Also worth keeping in mind that with low resistance items like notional 3kW heaters, they are often quoted as 3kW at 240V (which suggests an element resistance of 12.5 ohms) but that is only 2875W at 230V. So small shifts in voltage make a noticeable difference. Factor in the effect of the load on the actual voltage drop on the lead and you can get quite substantial amount of load shedding.
Say its a 1.5mm^2 flex and assume 24mOhm/m round trip resistance. Try and draw 20A through 20m of that, and you have just dropped another 600W of load.
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John.

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Two 3 Kw kettles on the same extension should have blown the plug fuse and quickly.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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Dave Plowman (News) wrote:

A 13A fuse is required to carry 1.6x the rated current without blowing, and only required to blow within 30 minutes for 1.9x rated current, so whether, or how quickly it should blow, depends on the duty cycle of the two kettles ...
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