Forums.MrPLC.com > Wiring question

SandyB

May 21 2009, 08:09 AM

If you are going from a 60A main to a 30A Dsconnect fused for 15A does the wired size need to be rated to 15A or 30A according to NEC???

stickman47

May 21 2009, 08:14 AM

The wiring from the 60 to the 30 needs to be sized for 60 amp. Keep in mind that THHN or THHN-2 is rated at 90 degrees c., but most switchgear is rated at 60 deg.C so you have to size the wiare accordingly. Your secondary wiring can be sized acording to the load (15a) but the de-rating factor for 60 deg. is still in effect. The best source for information is the UGLY's book. It has the derating tables.

SandyB

May 21 2009, 08:36 AM

QUOTE(stickman47 @ May 21 2009, 09:14 AM) [snapback]82502[/snapback]

The wiring from the 60 to the 30 needs to be sized for 60 amp. Keep in mind that THHN or THHN-2 is rated at 90 degrees c., but most switchgear is rated at 60 deg.C so you have to size the wiare accordingly. Your secondary wiring can be sized acording to the load (15a) but the de-rating factor for 60 deg. is still in effect. The best source for information is the UGLY's book. It has the derating tables.

Thanks!!