[RE-wrenches] Parallel Wire combining

[boB at midnitesolar.com]

The only thing I can think that AWG/KCMIL means is that it is a ratio ?

boB


On 12/2/2014 4:18 PM, boB at midnitesolar.com wrote:
>
> 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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