how long will regular romex last outside?

Answer 1

Regular romex (Type NM or NM-B) is not a good choice to use in direct sunlight or direct burial because the outer insulation (sheath) will decay from the UV rays from the sun, and if it is in contact with moisture, it can also begin to rot the sheath away. Once this happens, this process then begins on the insulation on the wires themselves. Eventually, once the insulation on the wires is degraded enough and water gets inside the sheath on a rainy day, it will conduct enough current from the line to the ground running next to it inside the sheath and start an arc. The resulting heat burns away the insulation quickly, and a dead short will develop in usually less than a minute afterward. I have seen this happen to regular romex both used overhead and buried. Some of it lasted almost 20 years, but did not have power except for about a 2 week period each year, and was shaded by trees. I have seen newer stuff last only 2 years or so before it failed.

There is a type of romex that is suitable for overhead and burial that is marked "type UF" The insulation on this wire is UV resistant, and much stronger, and completely encases the wires inside. It is not much more expensive than regular NM romex, and well worth the extra cost, just for the aspect of safety alone.

Answer 2

That depends on the environment it is in. Is it subject to abrasion or laceration? Hot and dry or cool and damp etc. . While it may work for a temporary use, I would suggest using the proper type of wiring with proper installation for exterior use.

Answer 3

I have had three six foot strips exposed to the weather on my patio since I built it in 1995 and other then a little discoloration the wires are still solid.

Answer 4

A long time if its not moved around or eaten into my mice and squirrels.

mike