I am installing a pond fountain and need to bring electric to the pond edge. I will trench a line from the house to a waterproof receptacle. the question is should I bury the 12ga NM wire inside flexible gray conduit or go with NMWU cable without conduit. The cable will be traveling thru some pretty juicy territory before terminating at the receptacle box.
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Regular NM wire, or Romex, is not rated for use underground even if it's in a conduit. You could run conduit and install individual THWN wires, or use the direct bury NMWU stuff.
Personally, I would never direct bury, always run conduit if you can. You never know when you'll want to run something else in that same conduit. If I recall, you can direct-bury 12" deep if you're feeding with a 15 or 20A, 120V GFCI-protected circuit. Otherwise, it's 18" deep in PVC, and 24" deep for regular direct-burial. I'd have to flip open the code to double-check those figures, but I think that's accurate. So, if you went to PVC conduit instead of a direct bury 120V GFCI line, it's only another six inches of digging.
I've done these sorts of set-ups both ways: direct bury and in conduit. For a relatively low load like a pond fountain (let's be clear: I'm talking ~1 amp @ 120V when I say "fountain") I'd just run NMWU. You cannot use NMWU in conduit for the run, but you do need to use conduit or a similar protection for the cable as it comes up to the receptacle head.
If you were running a pond PUMP (my current pump runs ~4amps), lighting, a UV clarifier, etc.. I'd spend the time and effort and run THWN in conduit.
In my experience, getting involved with a water feature is addictive, and you end up wanting more/bigger/etc... in short order.
Once you've stripped the ends off a few lengths of NMWU, you come to appreciate the ease of working with THWN - and also the resistance of NMWU to damage!
-t
It appears that in Canada. I am guess that with the reference to NMWU.
To the others that is a reference to a direct burial, wet cable that is similar, but I don't think that it is identical to the UF, underground feeder, used in the US.
So the other comments about burrial depth might be different also.
"pretty juicy territory "
Vas is das?
Do you mean swampy?
William the Geezer, the sequel to Billy the Kid - Shoe
Thanks for your input. I have worked with NMWU and yes it is no fun stripping off the insulation, but it does give me heart that the stuff is pretty bullet proof. I guess I will run with that stuff w/o conduit (except as stated, where it come out of ground). The pond is very boggy at the edges and I am sure I will run into water as I trench. I believe the NMWU will resist the water and wet conditions best.
>> I believe the NMWU will resist the water and wet conditions best.<<
This must be a very serpentine path this circuit must run since I cannot believe that NMWU will surpass the water resistant properties of rigid PVC conduit with properly glued up and cured joints and fittings.
You know you can bend it with relative ease and it has a fair amount of flex in small diameters (1/2" & 3/4") even without adding any heat.
If you have a shop vac, string and a sammich bag - you don't even need a fish to get THWN into the conduit.
Hit a PVC conduit with a shovel and you most probably have a nick but no penetration, hit NMWU and you may have a hole in the outer jacket. Easier to fix the PVC.
Maybe I should go check on my PVC household drains, the traps especially since they are wet 24/7........
Jim
Never underestimate the value of a sharp pencil or good light.
Buried conduit is a wet place anyway. While it might be "sealed" from ground water in most climates moist air will get into it and condensate..
William the Geezer, the sequel to Billy the Kid - Shoe
Understood.
I am still heavily biased toward conduit for underground runs. Dug up a few too many UF and direct burial service runs which "will never get hit".
Appears that many folks seem to "lose their ruler" when burying cable, especially the lighter UF runs such as this one.
JimNever underestimate the value of a sharp pencil or good light.
Flexible conduit should not be used for burial. You should use schedule 40 or schedule 80 PVC or schedule 40 steel. No flex conduit.