[RE-wrenches] Parallel Wire combining

[boB at midnitesolar.com]

I'm pretty sure that  Daniel Young's explanation of surface area 
explains the discrepancy.

The surface area of a larger wire does not grow as fast as its cross 
sectional area so
it does not cool as well.  It can carry more current but its surface and 
temperature
rise is going to be higher if you simply put more amps through it 
proportional
to the wire area.

But the wire table does not show multiple wires in parallel and/or the 
distance
between them.  Or is there such a table ?  If the distance between them 
are high
enough so that the heat can be dissipated, then you ~should~ be able to get
3 times the ampacity of all 3 wires in parallel ?  Shouldn't he ?

What exactly does the title of that column mean ?  AWG/KCMIL ?
AWG and KCMIL are different.  AWG goes higher as the wire gets smaller.
KCMIL (area) gets higher as the wire gets bigger.

boB




On 12/2/2014 3:32 PM, Larry wrote:
> Hey boB,
>
> This is the reference table I was using. They show 325 AWG and 325kCM 
> refer to the same diameter cable but I should have used kcm for clarity.
>
> If all insulation/temp rating is the same we are back to my original 
> question. Anyone else able to explain this? To be safe I am leaning 
> toward using the combined CM number to size for current rather than 3 
> times the ampacity as that just makes no sense to me.
>
>
> On 12/2/14 3:54 PM, boB at midnitesolar.com wrote:
>>
>> The "area" of the conductor will be 3 times and you would think that 
>> the NEC Ampacity would also be 3 times
>> that of one conductor.   But one LARGE conductor with the same area 
>> might not be as high as you think
>> because of insulation.  I would think that ampacity of 3 cables in 
>> parallel would be 3 times.  But probably
>> not when you take a single cable of the 3X area out of the NEC 
>> table.  (I haven't looked at this to verify)
>>
>> Also,  Larry,  325 AWG 750 AWG (gauge) wire is a bit too small for 
>> this, don't you think ?
>>
>> I know...  You mean circular mils...
>> boB
>>
>>
>>>
>
>
>
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