How much current safe for 30m extension?

I am in the UK (so mains voltage is about 230V or 240V).

I have a reel of main extension cable made of 3-core 1.0 mm^2 wire
rated at 10 Amps. So the nominal power rating would be about 2,400
Watts. (Link to tech reference for the cable is below.)

In uk.d-i-y Sammo <noone_at_no-where.com> wrote:
I am in the UK (so mains voltage is about 230V or 240V).

I have a reel of main extension cable made of 3-core 1.0 mm^2 wire
rated at 10 Amps. So the nominal power rating would be about 2,400
Watts. (Link to tech reference for the cable is below.)

It's always going to be safe, as it's got a fuse.

Ok...
Copper has a resistivity of 0.7*10^-8 ohms/meter.

Or, for a 1mm^2 wire, 0.7*10^-2 ohms/meter.
1.7*10^-2
Or for 2 wires, 1.4*10^-2 ohms.
3.4*10^-2

Or for 60m, 8.4*10^-1 ohms, or .84 ohms.

Or for 60m, 8.4*10^-1 ohms, or .84 ohms.

On Sat, 12 Feb 2005 12:46:19 UTC, Ian Stirling <root_at_mauve.demon.co.uk
wrote:

Or for 60m, 8.4*10^-1 ohms, or .84 ohms.

Plus the resistance on the two connections. Not sure whether the earth
fault loop impedance is still OK...

Sammo wrote:

I am in the UK (so mains voltage is about 230V or 240V).

I have a reel of main extension cable made of 3-core 1.0 mm^2 wire
rated at 10 Amps. So the nominal power rating would be about 2,400
Watts. (Link to tech reference for the cable is below.)

Presumably the current carrying capacity or power delivery capability
of the unwound 30m length unwound is going to be a bit less than 10
Amps/2,400 Watts due to losses along the length of the cable itself.
Is the reduction in current/power carrying capability significant? If
so, then is there a rough guideline figure for available current/power
which I can use?

If I take *two* of these 30m reels then I can join them with the
standard UK 13 Amp plug and socket supplied on the reels. This gives
me an overall length of 60m. Taking into account losses, what would
be the current carrying or power delivery carrying capability of the
60m length if all the 60m cable is unwound?


30 metres at 10 amperes isn't going to be a problem - so I have
considered just the longer lengths.

Basically, you have two factors to consider:

The first is how hot the wire will get. Now, provided that the cable is
unwound and in the open air, then its length is immaterial. If you coil
the cable up or cover it in something that restricts the flow of heat
from it, that is a different matter. However, for an unwound cable, the
rated current, say 10 amperes, is the maximum that is allowed due to
heat constraints. Pass more current than this and the wire will get too
hot. Pass a lot more current than this and the insulation could fail.

The second is the volt drop. Its resistance is about 0.02 ohms per metre
- so a 60 m length will have a resistance of 1.2 ohms and will drop 1.2
volts per ampere. A 120 m length would drop 2.4 volts per ampere.

Now the equipment at the far end of the cable will have a specified
range of input voltage for which it was designed. You must simply ensure
that it gets the minimum rated voltage, or higher, at the current it
draws. This minimum voltage will depend on the equipment type.

As a rough guide, losing 12 volts in 240 is probably going to be fine.
So, you could use a 60 metre cable at 10 amperes or 120 metre cable at 5
amperes.

If your load is happier with a lower minimum voltage, say 220 volts,
then you could run the 120m cable at about 8 amperes. However, you would
still be limited to 10 amperes for the 60 metre cable, because 10
amperes is the most the cable should be used to carry, irrespective of
length.

Purely resistive loads, like heaters, aren't terribly fussed if their
voltage is a bit low - so you could happily run a 2kW heater at the end
of 120 metres of your cable. If you have a lamp plugged in at the far
end, then it will get noticeably dimmer when the heater is switched on.
This isn't a safety problem, although it might appear so.

Some loads are very fussy about their minimum voltage but even those
should be happy with 10 amperes taken from your 60 metre cable.

Short current is some 120A, plenty to blow a 10A fuse quite prombtly.

OOPs! Yes, I forgot it was twin flex.

I am in the UK (so mains voltage is about 230V or 240V).

I have a reel of main extension cable made of 3-core 1.0 mm^2 wire
rated at 10 Amps. So the nominal power rating would be about 2,400
Watts. (Link to tech reference for the cable is below.)

Presumably the current carrying capacity or power delivery
capability of the unwound 30m length unwound is going to be a bit
less than 10 Amps/2,400 Watts due to losses along the length of the
cable itself.

Is the reduction in current/power carrying capability significant?
If so, then is there a rough guideline figure for available
current/power which I can use?

If I take *two* of these 30m reels then I can join them with the
standard UK 13 Amp plug and socket supplied on the reels. This gives
me an overall length of 60m. Taking into account losses, what would
be the current carrying or power delivery carrying capability of the
60m length if all the 60m cable is unwound?