Don't know if you will see this as its an older post. I agree with your math about there not really being any induction heating possible. Over on the FB group RVElectricity there is a current post about some park that burnt up because they think someone misused a 50->20 (or similar) type adapter and melted a cord.
One of the side topics that came up, as always, is to never leave your cord coiled up, it will get hot. There are several "movie set electricians" who say you need to roil your cords up in a figure 8, that will avoided any heating. Since you do sound work I figure you must have heard or seen this theory. I don't see how a figure 8 (or square or trapezoid,...) could be any better that a circle rolling up cable. Especially since we just said/proved that induction is not an issue.
You are correct. There’s no appreciable inductive heating effects on conductors at 60 Hz.
The real reason for figure-8 cable wrapping storage is that it allows you to wrap the cables without any twists. Plus you can use a standard road case for storing and transporting heavy feeder cable.
Thanks for taking the time to reply. I didn't think shape mattered. Is it possible that movie sets use DC power for equipment? Or some other factor I'm missing?
I'm not going to try and debate the guys who basically told me "not to argue with a pro". Unless I can go to a movie set, do some measurements and try to understand why they say figure 8 wires don't get hot but coiled does isn't worth it.
I have a cord reel for my 50A "standard" power cord (I think 6-6-6-8?). The cord is 35 ft, and the instructions call for it to always be fully unwound before use. I have not noticed any cord heating when unwound. I often don't need the full length. Would it be reasonable to try using it while still on the cord reel as long as I keep an eye on the temperature?
Correct me if I’m wrong but i seem to recall you writing about this before. However, I believe it was in the context of using, say, a 14 gauge cord plugged into an 15 amp outlet to run an RV AC. Didn’t you say then that there would be a considerable amount of heat…up to the point of melting/igniting? And a coiled cord would hasten the process? Thanks for keeping us safe!
Mike,
Don't know if you will see this as its an older post. I agree with your math about there not really being any induction heating possible. Over on the FB group RVElectricity there is a current post about some park that burnt up because they think someone misused a 50->20 (or similar) type adapter and melted a cord.
One of the side topics that came up, as always, is to never leave your cord coiled up, it will get hot. There are several "movie set electricians" who say you need to roil your cords up in a figure 8, that will avoided any heating. Since you do sound work I figure you must have heard or seen this theory. I don't see how a figure 8 (or square or trapezoid,...) could be any better that a circle rolling up cable. Especially since we just said/proved that induction is not an issue.
You are correct. There’s no appreciable inductive heating effects on conductors at 60 Hz.
The real reason for figure-8 cable wrapping storage is that it allows you to wrap the cables without any twists. Plus you can use a standard road case for storing and transporting heavy feeder cable.
Thanks for taking the time to reply. I didn't think shape mattered. Is it possible that movie sets use DC power for equipment? Or some other factor I'm missing?
I'm not going to try and debate the guys who basically told me "not to argue with a pro". Unless I can go to a movie set, do some measurements and try to understand why they say figure 8 wires don't get hot but coiled does isn't worth it.
Thanks again.
Mike,
I have a cord reel for my 50A "standard" power cord (I think 6-6-6-8?). The cord is 35 ft, and the instructions call for it to always be fully unwound before use. I have not noticed any cord heating when unwound. I often don't need the full length. Would it be reasonable to try using it while still on the cord reel as long as I keep an eye on the temperature?
Yes, that’s what I would do…
Correct me if I’m wrong but i seem to recall you writing about this before. However, I believe it was in the context of using, say, a 14 gauge cord plugged into an 15 amp outlet to run an RV AC. Didn’t you say then that there would be a considerable amount of heat…up to the point of melting/igniting? And a coiled cord would hasten the process? Thanks for keeping us safe!