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Old 11-01-2011, 12:44 PM   #1
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can somebody explain the pysics behind


when conductor (wire) travels more vertically, why does it get hotter and needs more insulation (MC for going between floors) than when it goes more horizontally? i'm just curious in the physics behind this phenomenon.

thanks

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Old 11-01-2011, 01:03 PM   #2
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can somebody explain the pysics behind


The wire heats up as current flows through it, the greater the number of amperes the more it heats up.

Air around the wire cools it down, the air moves upwards as it warms up by the wire. (warm air rises)

The vertical wire the same air moving vertically tends to follow the wire so the warmer air it gets it doesn't cool the wire higher up as quicklyu compared with a horizontal wire where different air moves upwards all along the length of the wire.

Then the air transfers the heat to other things like the subfloor or top of the stud cavity above.

I think that the effect of cooling on a vertical wire versus a horizontal wire makes little if any differnece in terms of having to use fewer amperes than the wire normally calls for (called derating); I think you do not have to derate because the wire is hung vertically. In other words the original question is for scientific purpose only, those doing electrical work can ignore it.

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Last edited by AllanJ; 11-01-2011 at 05:38 PM.
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Old 11-01-2011, 01:13 PM   #3
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can somebody explain the pysics behind


thanks. makes sense.
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Old 11-01-2011, 02:34 PM   #4
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can somebody explain the pysics behind


never heard this before. makes sense though. If your wires are getting hot, there is a problem
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Old 11-01-2011, 03:08 PM   #5
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can somebody explain the pysics behind


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Originally Posted by amakarevic View Post
when conductor (wire) travels more vertically, why does it get hotter and needs more insulation (MC for going between floors) than when it goes more horizontally? i'm just curious in the physics behind this phenomenon.

thanks
Does not make sense according to my mental image of the setup and what I understand about radiative, convective and conductive heat loss.

Can you provide specifics - temps, distances, other factors?

Last edited by Yoyizit; 11-01-2011 at 03:11 PM.
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Old 11-01-2011, 09:13 PM   #6
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can somebody explain the pysics behind


heres what i picture. But i don't believe it has any real world application because wires shouldn't be warm in the first place


The warm air on the vertical wire stays around the wire, while the horizontal wire the air moves away
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can somebody explain the pysics behind-warm-air-rises.jpg  

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