Parallel Conductors NEC 310.4

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tlona1

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Does anyone know the reason why you cannot parallel conductors less that 1/0? I am installing a 100 sub-panel and would like to run parallel #6
 
I think it has to do with physical strength. The smaller conductors are not a strong. If one breaks, then the entire 100 amps would pass through the other, and that could result in any number of bad things.
 
charlie b said:
I think it has to do with physical strength. The smaller conductors are not a strong. If one breaks, then the entire 100 amps would pass through the other, and that could result in any number of bad things.
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Wouldn't it be kind of obvious if you broke one pulling them in?
 
This is thread reminds me of many of the conversations I have with my three year old daughter. :grin:

tlona1: I want to parallel #6 AWG conductors.
NEC: No. You can't do that.
tlona1: Why not?
NEC: BECAUSE I SAID SO!!!!!!

Seriously though, I agree with charlie. There isn't an electrical reason that it wouldn't work; if you parallel two identical conductors, regarless of their size, current will split evenly between them. The NEC must be concerned about the physical aspect of the installation.
 
I bet it has more to do with cost and availability of conductors when you start parallelling above 1/0. Sort of the same issue as why you can't use white tape on conductors 6 or smaller
 
I was told that with smaller conductors it becomes much more critical that they be the same length or you can have overloading issues.

Also there is no need to run parallel conductors that small, I don't start thinking parallels until we max out 600 CU. In other words we run single sets until we get above 400 amps.
 
I think we can only guess at why. But I have a different guess than Charlie.

For smaller wires, small differences in wire size, material, and temperature, will make a bigger difference in how the current splits.

For larger wires that are installed correctly (each installed in the same manner), you are much more likely to get an even split.

Steve
 
My reasoning for using the parallel #6 is simple. This is going in my house and I already have the #6 wire and will therefore save me the $300 bucks it would cost for the higher gage wire
 
tlona1 said:
My reasoning for using the parallel #6 is simple. This is going in my house and I already have the #6 wire and will therefore save me the $300 bucks it would cost for the higher gage wire
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The NEC is really not in the business of saving folks money.

I know that seems like a wise guy response but it is the truth.

Now do you really need a 100 amp sub or would 60 amps do it fine?
 
I know its a little off the subject. But another reason to parallel in today's market. We are doing a parallel now. Two 2" emt with 3 - 3/0 in each. Total wire cost today not counting ground wires. = 2667.00
Total wire cost today using 500 kcmil = 4063.00 this is just the wire.
The cost difference on the emt is also a good savings as well.
The bigger reason however is I can't fit the larger raceway.
 
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