NMD Splice in a Conduit Body

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Aug 3rd, 2021 1:12 pm

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Jul 30th, 2021 8:28 am

BoatyMcBoatface [OP]: Member; Jul 31, 2017; 422 posts; 509 upvotes; Toronto

Jul 30th, 2021 8:28 am

NMD Splice in a Conduit Body

I'm running power to a shed and have a 40' run inside to the exterior exit. I was hoping to use NMD to the exit and then switch to underground wire. However, where the cable exits is not a great place for an accessible junction box. I was hoping to make the splice in the conduit body on the outside wall. I suspect that this is considered a wet location though so i can't put NMD into the conduit body? I presume people use NMD when they are wiring an external outlet though so could I put a weatherproof outlet box and make the splice in that?

Is there a code compliant way to avoid the internal junction box without running wet cable to the panel?

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Jul 30th, 2021 12:25 pm

middleofnowhere: Sr. Member; Dec 6, 2020; 937 posts; 1043 upvotes

Jul 30th, 2021 12:25 pm

It's technically not allowed to run multi-conductor cable (including NMD) inside conduit. If you are getting this work inspected, whether you can get away with NMD or NMWU (outdoor cable) inside conduit depends on the whims of the inspector.

All splices must be accessible for future electrical work. You cannot splice wires inside conduit tubing.

You can run NMD to electrical boxes on outside walls and make splices in weatherproof electrical boxes. Note: you cannot install an outfoor outlet on the same circuit as the shed as outdoor outlets are required to be on dedicated circuits.

Make sure you account for voltage drop when sizing your cable.

Finally, give some thought to future-proofing your shed electrical hookup. If there's any possibility you might need more than one circuit in the future, run heavier gauge 3 conductor cable (e.g. 8-3 for 50 amps) now so you can upgrade later without needing to dig another cable trench.

+1

Jul 30th, 2021 1:03 pm

Ballroomblitz1: Deal Addict; Oct 2, 2018; 2644 posts; 3135 upvotes; Toronto

Jul 30th, 2021 1:03 pm

middleofnowhere wrote: ↑ It's technically not allowed to run multi-conductor cable (including NMD) inside conduit.

Interesting, what would the reasoning be on this one? I dont have a need just curious....

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Jul 30th, 2021 2:16 pm

BoatyMcBoatface [OP]: Member; Jul 31, 2017; 422 posts; 509 upvotes; Toronto

Jul 30th, 2021 2:16 pm

middleofnowhere wrote: ↑ It's technically not allowed to run multi-conductor cable (including NMD) inside conduit. If you are getting this work inspected, whether you can get away with NMD or NMWU (outdoor cable) inside conduit depends on the whims of the inspector.

All splices must be accessible for future electrical work. You cannot splice wires inside conduit tubing.

You can run NMD to electrical boxes on outside walls and make splices in weatherproof electrical boxes. Note: you cannot install an outfoor outlet on the same circuit as the shed as outdoor outlets are required to be on dedicated circuits.

Make sure you account for voltage drop when sizing your cable.

Finally, give some thought to future-proofing your shed electrical hookup. If there's any possibility you might need more than one circuit in the future, run heavier gauge 3 conductor cable (e.g. 8-3 for 50 amps) now so you can upgrade later without needing to dig another cable trench.

Thanks, I was just going to run 10/2 for a 20A circuit for lights and outlets, there aren't any tools etc as they are all in the garage. This is what I was hoping to make the splice in (not in the body of the conduit)

It's weatherproof and accessible so that's why i was hoping to get away with splicing on the outside

Jul 30th, 2021 2:44 pm

middleofnowhere: Sr. Member; Dec 6, 2020; 937 posts; 1043 upvotes

Jul 30th, 2021 2:44 pm

From a code perspective, several esoteric rules determine if it's allowed to make a splice in that type of conduit body. The fitting must be permanently marked with its internal volume (used for box fill calculations) to be an acceptable junction box.

From a practical perspective, what you want to do will certainly work and probably won't cause inspection issues unless you draw an inspector with an attitude problem.

Jul 30th, 2021 2:48 pm

middleofnowhere: Sr. Member; Dec 6, 2020; 937 posts; 1043 upvotes

Jul 30th, 2021 2:48 pm

Ballroomblitz1 wrote: ↑ Interesting, what would the reasoning be on this one? I dont have a need just curious....

No idea.

It may be something as simple as the cable manufacturers being unwilling to pay to have their cables tested by UL/CSA for use inside conduit.

+1

Jul 30th, 2021 10:19 pm

jzmtl: Deal Addict; Jun 14, 2008; 4356 posts; 3214 upvotes; Montreal

Jul 30th, 2021 10:19 pm

Ballroomblitz1 wrote: ↑ Interesting, what would the reasoning be on this one? I dont have a need just curious....

Heat dissipation.

BoatyMcBoatface wrote: ↑ Thanks, I was just going to run 10/2 for a 20A circuit for lights and outlets, there aren't any tools etc as they are all in the garage. This is what I was hoping to make the splice in (not in the body of the conduit)

images.jpg

It's weatherproof and accessible so that's why i was hoping to get away with splicing on the outside

Yes this is fine for making joints.

+3

Jul 30th, 2021 10:45 pm

1chinaman: Sr. Member; Jan 19, 2013; 690 posts; 603 upvotes; Ottawa

Jul 30th, 2021 10:45 pm

If the lb body has internal volume listed in it , can be used a jb.
Minimum would need to be 3/4 in for code, 1/2 does not have enough internal volume from what I’ve read.

+1

Aug 3rd, 2021 1:12 pm

BoatyMcBoatface [OP]: Member; Jul 31, 2017; 422 posts; 509 upvotes; Toronto

Aug 3rd, 2021 1:12 pm

Just to update. The Conduit body wasn't deemed acceptable to run the NMD into, so i just had to switch it to a round weatherproof junction box and all is good!

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