4/0 conduit sizing??

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You will need to use the ampacities shown in Table 310.16 for this installation. 4/0 AL USE = 180 amps at 75C. It looks likes the ampacities the manufacture is showing is similar to those in Annex B and would require calculations from an engineer.
 
My reply was to the inflated ampacity the manufacture was listing for this cable. What is the calculated load for this service? I don't feel Table 310.15(B)6 is intended to apply to parallel conductors but others may feel different. If your calculated load is less that 360 amps 2 sets of 4/0 AL conductors would still be compliant using Table 310.16 (180 amps X 2 = 360).
 
pjwinstalls said:
But table 310.15 (B)(6) states that 4/0 is 200amp allowable when used for residential service entrance conductors.
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You can not use Table 310.15(B)(6) as basis for parallel conductors.

You use Table 310.15(B)(6) only as shown or you go to 310.16.
 
Bob,
You can not use Table 310.15(B)(6) as basis for parallel conductors.
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There is a panel statement that says otherwise. Note 3 in the older codes was what is now 310.15(B)(6).

Proposal 6-74 in the 95ROP was to prohibit the use of the reduced wire sizes in parallel. Panel 6 rejected the Proposal with this statement: "Conductors 1/0 and larger are permitted to be paralleled by section 310-4. This would apply to Note 3."

Don
 
Pierre,
That may have been the intent, but where in the '05 does it actually state that. I do not see it saying other than what Bob has posted.
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The wording doesn't say you can't and that part of the rule has not really changed since the panel issued its statement.
Don
 
The wording in the title and the positive language before the table says: "3 wire"

As per the wording in 240.21(B & (C), parallel conductors are considered as more than just 3 conductors... therefore it would seem that it is not permitted.
 
Pierre,
It is my opinion that "three wire" has to do with the type of circuit, that is 120/240 volt single phase, and not the number of conductors used in the circuit. That wording is to make sure that this table is not used for a dwelling service that has been derived from a 208/120 volt wye system.
Don
 
don_resqcapt19 said:
Bob,
You can not use Table 310.15(B)(6) as basis for parallel conductors.
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There is a panel statement that says otherwise. Note 3 in the older codes was what is now 310.15(B)(6).
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Don I am not sure I agree with you that the CMPs statement allows the paralleling of conductors based on Table 310.15(B)(6) and I believe you have been on my side of this parallel conductor issue in the past. :lol:

310.15(B)(6)120/240-Volt, 3-Wire, Single-Phase Dwelling Services and Feeders. For dwelling units, conductors, as listed in Table 310.15(B)(6), shall be permitted....
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IMO as listed means exactly that, as listed in the table.

Table 310.15(B)(6) is not an ampacity table.

It simply says we can use X size conductor for X size OCP as you are well aware that table does not change the rating of the conductor.
 
Bob,
Don I am not sure I agree with you that the CMPs statement allows the paralleling of conductors based on Table 310.15(B)(6) and I believe you have been on my side of this parallel conductor issue in the past.
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That was before I found the panel statement. :twisted:
Don
 
don_resqcapt19 said:
That was before I found the panel statement. :twisted:
Don
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Fair enough. 8)

IMO due to the wording in the text of 310.15(B)(6) that I pointed out the panel was wrong in making that statement.

As Listed is very clear and straight forward in my opinion. 8)
 
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