Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums > AC Power and Grounding
coiling feeder cable
Stephen Swaffer:
Take a look at conduit conductor count deratings to get a picture of how quickly heat dissipation can become an issue. Conductor ampacities are based on insulation temperature ratings-most of these are high enough to make a hand warmer. Bundle a bunch together and you have lots of heat. Just common sense-if you think about the physics behind the rules in the NEC. Just like thinking about the physics involved in setting up a sound system.
Dave Garoutte:
--- Quote from: Chris Hindle on March 31, 2021, 08:50:48 AM ---But also induction heating to the closely coupled loops of cable.... as I understand it.
At a "big show" I teched one winter last century, the over/under 50 odd feet of 400A feeder made a nice hand warmer. The feeder itself (away from the loop) was cool to the touch.
Chris.
--- End quote ---
A stacked coil of 'heater' wire will have way less surface area to dissipate said heat compared to a single strand laid out.
Erik Jerde:
--- Quote from: Stephen Swaffer on March 31, 2021, 12:36:20 PM ---Take a look at conduit conductor count deratings to get a picture of how quickly heat dissipation can become an issue. Conductor ampacities are based on insulation temperature ratings-most of these are high enough to make a hand warmer. Bundle a bunch together and you have lots of heat. Just common sense-if you think about the physics behind the rules in the NEC. Just like thinking about the physics involved in setting up a sound system.
--- End quote ---
I can attest to that. I was climbing in an attic space over a stage once and I laid hands on a very warm piece of 3/4” EMT that was serving the lighting system. I don’t know how many circuits or what the conduit fill was but it was just a hair uncomfortable to hold onto. Fortunately there was other structure around more appropriate to use for climbing.
Curt Sorensen:
A friend toured with Brit Row and was taught to alternate a coil (loop) and an eight. He said it evened out the build-up from the cross-overs when only figure eights are used. I assume every other coil is over-under. Luckily I don't deal with much bundled feeder these days, so no personal experience with that approach.
charles strickland:
I asked the question mainly for best practice reasons. on occasion I have an extra 20 ft or so cable to deal with, heat build up was my main concern. Thank you for the advice.
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