parallel conductors

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domnic

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What code cycle did the nec prohibit parallel of conductors smaller than 1/0 ????????????????????????????????????????????????????????????
 
The intent to prohibit parallel conductors existed in the code prior the the 1975 edition, however prior to the 2011 code the language never actually prohibited paralleling conductors smaller than 1/0.
 
They do not appear in the 1940 NEC but the 1947 states:

315. (3105) Conductors in Multiple. Conductors in sizes No. 0 to 500,000 c.m., inclusive, may be run in multiple, provided they have the same circular-mil area and type of insulation, and are the same length. etc.
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infinity said:
They do not appear in the 1940 NEC but the 1947 states:
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The language in the 1947 code has the same problem as the language prior to the 2011 code....in both cases they are trying to use a specific permission to prohibit something else. A specific permission to use 1/0 and larger in parallel, in no way acts to prohibit connecting conductors smaller than 1/0 in parallel.

Yes that was clearly the intent, but the code says what it says.

In the 2011 code the word "only" was added in a way that actually does act to prohibit using conductors smaller than 1/0 in parallel.
 
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