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Can indoor Romex be used in conduit for outdoor use? Answered

My friend is adding motion sensor lights outside at our house. He plans to install conduit in the garage, and use indoor 14/2 Romex, Type NM-B Indoor. He then will add the same outside to the security light fixture he is installing. Can indoor Romex in conduit be used for this? We live in the desert in Southern California, where temperatures can get over 120 degrees in the summer.


. Water/moisture is your main concern. If the Romex® is in water-tight conduit with no condensation, you will be OK. Pretty easy to do with rigid conduit (as long as it is never submerged), next to impossible with EMT. You may want to go with a water-resistant cable (NMC, NMW or UF) for any conduit runs that are exposed to the elements.
. If the lights and conduit are all under protective eaves you should be OK, but you ought to get a qualified person to eyeball it for you.
. Temperature shouldn't be a problem; NMB is rated for 90oC.
. Keep in mind that most (if not all) areas of the US require residential wiring to conform to the NEC and be inspected before being put in service. SoCal is probably very picky about this.

Sounds fine to me.

I'm pretty sure he can use indoor Romex as he is installing the wire inside a building. You might consider ditching the indoor conduit and just using it outside, were the protection is necessary, Check with building codes just to be on the safe side.