I found the cable (1533576 – Actuator/Sensor-Cable, M12 Socket – Open End Connector, 2m, 4A, 250V, Phoenix Contact) here that is claimed to handle 4 A and is then written that it has a 22 AWS cross section gauge, 4x 0.34 mm².
How this could possibly be? There is the table here that says the gauge 22 can is only allowed to carry 0.92 A for "power supply". Even all four wires together cannot make it as much as 4 amps. Ok it would be 7 amps for "chassis wiring" but if another answer about the chassis wiring is right this only applies for the single wire free in the air and not in the bundle. All 4 wires in this cable are very obviously in the bundle.
I was planning to use 14 gauge wires for my 5.5 A (5V) power part. They look thick and thinner wires worked fine on my workbench during prototyping. Does this mean that my power circuit is over-engineered?
The possible answers could be:
- Forget about this cable, you need the gauge 14 to supply exactly the power to that PCB to be safety compliant (5.9 A, your SBC draws 5.5 A so table calls for this gauge).
- Something else? Is it so that I do not actually need the wiring that heavy to be safety compliant? Or some consultant can waive this requirement?
Best Answer
Ampacity ratings for cables aren't hard numbers. Different insulation, different length, and obviously the environment all affect it. For example, the material information for that cable is pretty detailed and seems to use a polyurethane rather than your typical PVC.
I also do not think the 4A rating means 4A through every conductor at the same time. Probably just two.
14AWG wire for 5.5A is overkill though. An extension cord carrying designed to carry 15A is 14AWG. And on model airplanes, for example, they carry a lot more than 15A on 14AWG wire.