- Joined Sep 24, 2015
Depends on your definition of 'handle'. The fusing current of 14awg is 166 amps, but you can only use it at currents that don't damage the insulation. The title is 'How much current before it burns', not the wire melts or fuses. To some extent that depends on the rating of the insulation. Normal domestic/residential is 75 or 80C. Industrial is 90C. Specialist can be 200C or higher..This is a surprise to me. I wouldn't have expected 14 gauge to handle more than 30 amps. Cool video. As for accuracy? I don't see why it could be fake or some factor someone failed to take into account.
Depends on the welder. Some welders, like stick and TIG, are current sources so the voltage will be low when the resistance of the circuit is low. MIG welders are voltage sources. They rely on the wire burning back to raise the resistance of the arc to the equilibrium point.
My best guess is because the welder is driving what amounts to a close to dead short. The guy has maybe 2 to 3 feet of AWG 14 round trip so pretty close to a short. I was not a welder you have likely welded more in a 6 month period than I have in my life. I did work with quite a few welding machines and procedures for their verification. Open circuit voltages were as high as 90 volts on some. Actual arc voltages around 12 or 13 volts and some were adjusted by moving the weld head up or down from the workpiece. That on machines where the arc control voltage was preprogrammed. Anyway in this case the welding machine is working into close to a dead short. What I did not quite get was at 15 Amps the voltage was 0.350 volts and at 30 Amps 0.7 volts which makes sense but I had a hard time seeing the decimal point on his voltmeter. Then at higher currents as the current increased the wire got hotter and as expected the resistance started to increase and the voltage drop followed which is what I would expect. Anyway the welder supply was working into 6 feet about of AWG 14 so maybe 0.015 Ohm load. Thats my best guess. There was no arc.
I was once putting a lot more than 30 amps through a 14 gauge extension cord running across the floor. At some point I stepped on it and it just exploded. My theory was that it was barely managing to stay in thermal equilibrium and, when I stepped on it, I blocked the loss of heat to the environment somehow and it got real hot real fast,
Probably the explosion was caused by the quitr hot wires touching when you stepped on the cable. Insulation will deteriorate at those high temperatures. Some kinds of insulation will actually melt and flow. Then the smallest touch and a shorted circuit results and with enough power you can get an explosion and a blast of ARC FLASH that leaves a copper stained burn. AND, by the way, it is painful.
He is controlling current through a very good conductor (copper). Ohms law determines the voltage drop across the 4-feet of 14-gauge wire. At 0.0025 ohms per foot, and 40 amps applied, he should get, as measured, 1 volt.
Or the insulation had melted enough the you shorted it.I was once putting a lot more than 30 amps through a 14 gauge extension cord running across the floor. At some point I stepped on it and it just exploded. My theory was that it was barely managing to stay in thermal equilibrium and, when I stepped on it, I blocked the loss of heat to the environment somehow and it got real hot real fast,
Yeah, he measured voltage and current. At 15 amps wire cold he got 0.350 volts and at 30 amps he got about 0.700 volts which sounds about right. He did not measure or define wire length. You really have to watch the video to get the whole picture of what was going on. As the wire got hot you could see the voltage drop changing for an applied current as the wire resistance increased. Anyway it was all about what I would have expected to see. Also the wire used looked to be AWG 14 for example ROMEX about maybe 3 feet long. He shorted two conductors at one end and applied his current from the opposite end. Just watch the video.The basis for the electrical code current ratings for wires are temperature rise and voltage drop.
I did not watch the video, but I am wondering if there was a voltage reading across the ends of that wire in the test. That would have been useful and very educational.
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