NEC 2011 - Annex C & Chap 9 Table 8.
- Thread starter ck2013
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- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Why would annex C only include 600v or less. As far as I know there is no voltage rating for fill. Same for Table 8--- that is the wire size not including the insulation- 4/0 is 4/0 or 211600 if copper or aluminum 600v or less or more than 600v
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I didn't check each and every type condutor listed in Annex C, but the majority are definitely only used in 600V or less installations.
Table 8 diameters and area values should apply to any conductor regardless of voltage rating... as long as the stranding is as listed. And note that is dimensions excluding insulation.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
I agree- I was assuming that if the conductor was rated over 600V then it didn't matter. I hadn't realized that they are not listed in the table.
Thanks. I got a better understanding of Table 8 now.
Regarding Annex C, why only maximum number of conductors is provided? Usually we want to know whether we can fit the cables (conductor + insulation layer) in the conduit correct?
For example, 500KCM 25KV cable is much larger than 500KCM 600V cable because even though the conductor (copper) size is the same (500KCM) but the insulation thickness is very different. Table C.8 THHN type shows that four (4) 500KCM conductors can fit in 3" RMC conduit, so we should be able to fit (4) 500KCM 600V THHN cables in 3" RMC conduit since 600V insulation thickness is small. But you can not fit (4) 500KCM 25KV cables in the 3" conduit. Is my understanding correct?
- Location
- Connecticut
- Occupation
- Engineer
Yes, you want to know whether the cables (conductor + insulation) can fit. This is what Annex C tells you, the maximum number of conductor + insulation of various size and insulation type that can fit in specific conduit types and sizes.
Yes, your understanding is correct.
Annex C is provided for informational purposes only. The Tables in Annex C are based on the Requirements of Chapter 9.
- Location
- Illinois
- Occupation
- retired electrician
For any conductor or cable that is not listed in the Annex C fill tables you have to use the Chapter 9, Table 4 conduit areas and the area of the conductor(s) or cable(s) that you are using and do your own fill calculations.
The types of conductors listed in Annex C are the more common types and there is little variation in the area between the same type and size of conductor among the various manufacturers. When you get cables or conductors for voltages over 600, that is not the case and the fill must be calculated based on the area or OD of that conductor or cable. You would normally get that from the conductor or cable manufacturer.
The types of conductors listed in Annex C are the more common types and there is little variation in the area between the same type and size of conductor among the various manufacturers. When you get cables or conductors for voltages over 600, that is not the case and the fill must be calculated based on the area or OD of that conductor or cable. You would normally get that from the conductor or cable manufacturer.
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