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View Full Version : Using ROMEX® to feed subpanel, do I have to derate from Table 310.15(B)(6)



Mr_Magoo
09-23-2008, 11:21 AM
I want to put a subpanel in the garage. According to Table 310.15(B)(6), I would need #4 Copper for a 100amp subpanel. Is this table for individual conductors in conduit or can you use ROMEX® to feed the subpanel at 100amp? The reason I ask is I read that when using ROMEX® you had to derate the THHN in ROMEX® to the 60*C rating.

Thanks,
Mike

Mr_Magoo
09-23-2008, 12:30 PM
Further research has indicated that I do need to derate when using NM.

jwelectric
09-23-2008, 12:56 PM
Do just a bit more research and you will see that Table 310.16 must be used also

Speedy Petey
09-23-2008, 02:24 PM
You are not "derating" anything. NM cable simply must use the 60 deg C column.

IF you did need to derate the cable you would do so from the actual insulation temperature column which is 90 deg C.

Chris75
09-23-2008, 02:27 PM
I want to put a subpanel in the garage. According to Table 310.15(B)(6),

Thanks,
Mike


As already mentioned, you cannot use table 310.15(B)(6).