Southwire and other venders vs NEC

[82angelfan]

Due to an ongoing RFI regarding conduit fill, code vs key notes vs customer spec. Doing research I discovered that Southwire an another vender have a smaller diameter spec than the NEC code book. 4/0 OD of 0.627 vs NEC OD of 0.638.

How is it possible that Southwire can make a smaller diameter wire an still get listed? wouldn't it then be a code infraction every time someone used this wire?

 

[infinity]

How is it possible that Southwire can make a smaller diameter wire an still get listed? wouldn't it then be a code infraction every time someone used this wire?

No. Note #10 to the table clearly states that the numbers in the tables represent the worst case scenario. When the actual value is known that can be used.

Chapter 9: Note (10) The values for approximate conductor diameter and area shown in Table 5 are based on worst-case scenario and indicate round concentric-lay-stranded conductors. Solid and round concentric-lay-stranded conductor values are grouped together for the purpose of Table 5. Round compact-stranded conductor values are shown in Table 5A. If the actual values of the conductor diameter and area are known, they shall be permitted to be used.

 

[82angelfan]

Thanks. couldn't see the forest through the trees.

 

[infinity]

Thanks. couldn't see the forest through the trees.

You're welcome. It is an interesting question. Sometimes those Chapter 9 notes to the table don't get enough love.