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Feeder Soufflé

July 15, 2015

If you want to have some fun, try taking some feeder cable and putting it in your oven. First warm up your oven to something like 175° or 200° F for about 15 minutes or so to make sure it’s nice and hot. Then toss in the cable and let it bake for, oh, I don’t know…How long is your typical show? Two, three, four hours? Then put on some oven mitts, take the cable out of your oven, and plop it down on the counter to let it cool for an hour or so.

 

No, it’s not going to morph into a cobra or create some YouTubeable moment. But it will give you an idea of what you’re putting your cable through every time you put it in service. You see, when current flows through a cable, the resistance of the cable causes it to heat up. You’re essentially cooking it from the inside out. And what that does to the insulation or the jacket is similar to baking it in the oven. The harder you run the power distribution system, the hotter it gets and the more the insulation deteriorates.

 

You can get an idea of what’s happening on your show with your power distro equipment by touching it with your bare hand. Connectors are often one of the warmest because as they age and corrode they increase in resistance, which causes them to heat up more, which, in turn, can cause more corrosion, eventually leading to arcing and pitting. It’s a destructive cycle that can result in a melted mess.

 

Feeling power distro components is not ideal because you’re susceptible to shock if there are any cracks, holes, cuts, or abrasions in the insulation. A much better way is to use an infrared thermal imaging camera like a Flir. These handheld devices have a display, much like a video camera display, showing a thermal map of the picture and that allows you to monitor the temperature of cables and components without touching them. Any components that are hotter than the surrounding areas will show up as a white or yellow area. A tool like this makes it quick and easy to identify potentially troubling components at a glance so you can evaluate large systems quickly. The only problem is that some of these devices don’t come cheap. They range from about U$900 up to about U$7000 or, to put it in terms you might better understand, about a week’s pay for a touring electrician. (Earning Money in the Touring Industry)

 

If you want something similar with less of a financial liability, you might try the Flir One. It’s an adaptor for an iPhone or Android that gives you most of the capabilities of the handheld equivalent. I ordered one for my iPhone 6+ and in three to five weeks I’ll be able to post pictures and video from it. These devices can only measure temperatures up to 248° F (120 C°), which is much less than the top-of-the-line handheld (3000° F or about 1650° C), but if your cables and connectors are getting hotter than 120° C, then you need a Class C fire extinguisher, not a thermal imaging device.

 

Now that your feeder cable has had some time to cool off, feel the insulation. It’s probably brittle, dry, and ready to fall into pieces. If you uncoil it and stretch it out, chances are the insulation will crack or break, leaving exposed conductors. This is what you’re doing every time you put a conductor into service. The harder you run your power distribution system, the more you’re shortening its lifespan. Cables should last a good long time, and if you take care of them, treat them kindly and gently, they will give you years of safe service.

 

 

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