UF vs NM-B wire?


Old 02-17-06, 06:48 AM
Thread Starter
Join Date: Feb 2006
Location: NY state
Posts: 25
Question UF vs NM-B wire?

Could someone please tell me the difference.
I believe the UF-B is for outdoor wiring and perhaps dampness issues, also appliances like washing machines and dishwashers. I see a clear plastic wrapping around each wire that is not there on NM-B wire. Is this correct?
If so or if not, can a line with one type be combined with the other? Help is appreciated.
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Old 02-17-06, 07:09 AM
Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
UF is rated for outdoor use.

NM is not rated for outdoor use, and will eventually rot if it gets wet.

While you can use UF wire indoors where NM is permitted, UF is harder to work with.

To join the two together you simply wire nut them like any other two wires.

Washing machines, dishwashers and other "wet" or "damp" appliances do not need UF wire, they can be NM, assuming NM is allowed where you live.
Old 02-17-06, 07:17 AM
itsunclebill's Avatar
Join Date: Jan 2006
Location: Denver, CO area
Posts: 221
NM-B is normally used for dishwashers and washing machines in a residence.

UF (underground feeder) type cable is for underground installations. It can be used inside but seldom is for cost reasons. It may be used in place of NM-B IF the insulation rating is 90 Deg C. There is no issue with hooking the 2 types together using approved enclosures and splicing methods. UF may not be used where exposed to direct sunlight unless identified for such use.

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