Thread: Extension Lead Losses

A few years back I purchased a 10m 15amp lead to run from the generator to the panel.

Time to move the generator and while looking for a longer lead found my "extra heavy duty" lead is in fact 3 x 1.5mm.
I've purchased a 40m* 3 x 2.5mm lead to replace it, then I went looking for a loss calculator(ok maybe I got the order wrong there) to compare the two leads.
Well the calcs don't agree. So does this one pass a sanity check?
https://www.jcalc.net/voltage-drop-calculator-as3008
Vdrop 240V single phase 15A 2.5mm2 40m = 4.5% 10.81V
Vdrop 240V single phase 15A 1.5mm2 10m = 2.06% 4.95V

One of the other cals gives results around(but not exactly) half those......so fair to say I am missing something.


* will likely shorten this to around 20m at some stage. Which should make the losses ballpark the same as the 10m(I believe)

Originally Posted by Stustoys

A few years back I purchased a 10m 15amp lead to run from the generator to the panel.

Time to move the generator and while looking for a longer lead found my "extra heavy duty" lead is in fact 3 x 1.5mm.
I've purchased a 40m* 3 x 2.5mm lead to replace it, then I went looking for a loss calculator(ok maybe I got the order wrong there) to compare the two leads.
Well the calcs don't agree. So does this one pass a sanity check?
https://www.jcalc.net/voltage-drop-calculator-as3008
Vdrop 240V single phase 15A 2.5mm2 40m = 4.5% 10.81V
Vdrop 240V single phase 15A 1.5mm2 10m = 2.06% 4.95V

One of the other cals gives results around(but not exactly) half those......so fair to say I am missing something.


* will likely shorten this to around 20m at some stage. Which should make the losses ballpark the same as the 10m(I believe)

These numbers look correct to me. A calculation that gives half these values is only looking at the voltage drop on one wire - double that to get the full loop resistance.

Jack

This page is from ASNZ 3001 shows max length for 10A and 15A leads in normal use and "high" current applications. (welders, motors etc). As you found out " extra heavy duty cables " dont have larger conductors just thicker outer sheathing.

Originally Posted by Jack Ryan

These numbers look correct to me.

Thank you.

Originally Posted by Jack Ryan

A calculation that gives half these values is only looking at the voltage drop on one wire - double that to get the full loop resistance.

I'm not sure its that easy.(but really if the above link is correct I'm not that worried.)

I should have included a link and numbers
Vdrop 240V single phase 15A 2.5mm2 40m = 1.75% 4.2V (so less than 50%)
Vdrop 240V single phase 15A 1.5mm2 10m = 1.21% 2.91V(more than 50%
https://www.rapidtables.com/calc/wire/voltage-drop-calculator.html

I figured if it was just a "double length" issue it would at least be the same error(which I didn't exactly make clear in my OP)

Thank you Sparky I will have to keep that handy.


Now I just need a clever way of knowing when the mains come back on.

Originally Posted by Stustoys

I'm not sure its that easy.(but really if the above link is correct I'm not that worried.)

I figured if it was just a "double length" issue it would at least be the same error(which I didn't exactly make clear in my OP)

I think the numbers are close enough to suggest that it is that simple. I don't know where your data comes from but resistance is also a function of temperature and it might be that the on-line calculator used a different temperature. Other than the "double length" issue, there is little else that would cause a difference that is very close to a factor of two.

Even with the small discrepancy, I trust your issue is resolved.

Regards
Jack