Re: How much current safe for 30m extension?

From: Jerry G. (jerryg50_at_hotmail.com)
Date: 02/13/05 

Date: Sun, 13 Feb 2005 01:25:57 -0500

As long as the maximum current load does not exceed the current rating of
any of the cables that are used in the extension, it will be safe. There
should not be very much loss over a few hundred feet of extension. If there
is a loss, you can then change the extensions for ones that are of a larger
gauge.

I have run extensions of up to 400 feet. These were 10 Amp rated. I had no
performance loss in the loads that I was using. The load was about 4 to 5
amps. I am working with 120 VAC at my location. I took a voltage reading, at
the outlet, and one across the load. There was a drop of about one or two
volts. But, the total voltage at the extension output was still in specs
while under the load. The source voltage at the outlet was about 118 VAC.
Across the load, if I remember correctly, it was about approximately 116
VAC.

In areas that are using 220 VAC, the current is about 1/2 for the same
wattage, as when compared to 120 VAC. This would lead to less loss when
using an extension cord.

Most devices here in North America are rated at 105 to 125 VAC. Some are
rated from about 105 to 135 VAC. 

-- 
Jerry G.
======
"Ian Stirling" <root@mauve.demon.co.uk> wrote in message 
news:420dfa9a$0$45677$ed2e19e4@ptn-nntp-reader04.plus.net...
In uk.d-i-y Sammo <noone@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.
Or for 2 wires, 1.4*10^-2 ohms.
Or for 60m, 8.4*10^-1 ohms, or .84 ohms.
At 10A, 8.4V, or heating by 84W.
If at the plug end is 240V, at the socket end will be 232V, which is
(232^2/240^2)= .93444444444444444444
So, you lose 7% of the power for a heater, for example.

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