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2.5mm cable calculation

Can a 10amp 240volt aircond be connected to a 2.5mm cable enght 0f run 50mtrs

1 Answer from a MyBuilder Electrician

Best Answer


You don't provide enough information to accurately answer this question, it depends on the type of cable and the installation method and most importantly is the cable grouped with other cables and what is the ambient temperature... Also is this the only load on this cable? Or are you coming off a ring circuit with other loads on it?

Taking into account all factors above then I'd be surprised in a 2.5mm cable couldn't support a 10A load assuming there are no other loads on the circuit!

Your issue would be voltage drop, V=IxR, now we know I (10A) so you need R, based on 2.5mm copper conductor your looking at 18milli-ohm/A/m so for 50m you have V=(18x10Ax50m)/1000 therefore voltage drop = 9V.
Max allowable VD is 5% for non-lighting circuits ie 5% of 230V = 11.5V... Therefore it passes on VD also... Would guess your good to go!


Answered 8th Feb 2015

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