I've been looking at a device/power-supply pair I was sent recently for a project.
The device specs say it needs 24V and will draw 10A max.
The power supply provides 24V @ 9A (14A peak).
The power supply has 3 posts for V+ and 3 posts for GND (call them V0, V1, V2, G0, G1, and G2 respectively).
The cable that was supplied bundles 14 24 AWG wires, connected into a molex receptacle such that 2 wires go to V0, 2 to V1, 3 to V2, 2 to G0, 2 to G1, and 3 to G2.
I looked at a load-limit table for 24 AWG wire and it says that for chassis wiring, the wire is rated for 3.5A max and for power transmission 0.577A max.
Since the device can draw up to 10A, clearly a single piece of 24 AWG would be too small to be safe in this configuration.
The only conclusion I can draw from this is that using 7 wires across 3 terminals spreads the current load out such that 24 AWG is safe.
My questions, if you've managed to get this far are:
1) What is the calculation to determine the correct minimum number of smaller gauge wires to use in such a setup (i.e. where you're replacing a single larger wire)? Is it simply max current draw / number of wires?
2) How is the voltage drop due to the wire length calculated when using multiple wires (I know how to do it with one wire)?