NM-B can't be used anywhere outside - in conduit or not. If you have to buy wire I'd think about going with #12 and a 20 AMP breaker just so that oversized electric powered yard tool doesn't trip the breaker and shut off the bubbler for the fish (or whatever). You can still use a 15 AMP GFCI receptacle.

The crawlspace is not OUTSIDE. Stapled to the joists in a crawlspace may indeed be a dry location. However, this is one of the areas where local practice is highly variable.

NM is probably acceptable, but IMO using UF is good practice.

If I did not own wire already, I would not even ask, I would buy UF. Have you seen the price of wire lately!

The wire would be stapled to the joists.

I thought you could run NM through conduit. Am I mistaken? The conduit runs under a patio, outside.

I was going to run 12/2, but the landscaper already ran a line undergound away from the junction box and its 14/2 UF. Its a 15 amp breaker so I am ok, but I don't want to give the impression later that the breaker can be swapped out becuase a 12/2 wire is coming out of it.

BTW, the circuit will supply power to a low voltage lighting system. Water pump for water feature is in the distant future!

"I thought you could run NM through conduit. Am I mistaken? The conduit runs under a patio, outside."

You can put NM in conduit if the location is above grade and not subject to a wet condition. Hot temps aren't a factor, as most NM is rated for 90C. Don't install or work with NM at cold temps (-18C or lower if I remember correctly) as flexing will damage the nylon jacket and insulation.

In our area you could run NM cable for the 30' of crawlspace but you would have to use UF in the 25' of outside conduit.

Uh oh. No NM outside at all huh? Does anyone know why that is or if that is correct? I have seen and have used NM several times under houses (I guess you would call that outside) and also inside conduit-outside, sometimes above grade and sometimes below, sometimes pvc sometimes emt. Should this be replaced whenever I see it in the future or for things I have done in the past. We live down south and low temps during the winter rarely dip into single digits. Thanks for the help.

"to an outside GFCI socket, 25 feet of conduit - in a stone wall"

What did I read wrong? I said NM can't be used outside, conduit or not. That is where most stone walls wind up, although there are some pricey places that have them inside.

Single piece of cable, use UF. Make it hard - run NM-B in the crawl space, put in a J-box, then run the UF outside and into in the wall.

If the rock wall isn't outside just say so.

DARN you guys can complicate something simple sometimes.

Yes, yes, the stone wall is outside, but shouldn't conduit be considered 'inside' since its enclosed? Just kidding, I had to ask twice because it is not the answer I want to hear, but if thats the case, so be it.

Also, I had heard differently, where NM is OK in conduit, from several sources, thus my confusion.

The reason is that conduit outside (or underground) never stays dry. Infiltration, condensation - it gets wet inside.

BTW, when I said NM was OK, I misunderstood your application. I thought you were going through a stone foundation wall to install an outdoor receptacle on the side of the house. NM is OK for this, but UF is better. But that doesn't apply here.

Here is how I would do what I understand your job to be.

I'd go with UF the whole way. I would direct bury it, and protect it with schedule 80 PVC conduit where it enters the ground from the house, and where it emerges from the ground at the wall.

UF may be buried 12" deep if it's GFI protected at the source. Personally, I think that's too shallow (within easy range of a garden shovel). I wouldn't bury it less than 18".

Comments and corrections from the pros are most welcome.

Pros would install THWN (which is generally a dual listing with THHN) wire in the conduit. NM/UF in conduit is very amateur, except for short lengths of conduit for physical protection.