[Terabitdan]

Hello I’m installing a new sub panel and wonder if it’s to code to use EMT conduit from the panel up into the joist bay above, then attach a 4x4x4 box to use as a breakout box for NM cables? It’s less than 24” and I would run the NM through the box and conduit, stripping the jacket inside the panel with no splices. Doing it this way would provide a neat way to clamp all the NM and seal off the top of the raceway.

I know it’s ok to use the conduit and end it in the joist bay, just not sure if the box on the top makes it a raceway system.

There are five 12/2 NM which would go through the raceway, 2-2-2-4 SER, 1” and two 1/2” additional conduits coming from the 24 space panel. The wall will be finished on both sides which is why I want to use the conduit to protect the wires and make additional circuits easy to feed it needed.

Appreciate the help...

Dan


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[brric]

Don’t exactly understand what you are contemplating but a 4x4 may not be large enough.

 

[Terabitdan]

This is the idea. Using the 2” conduit as a less than 24” raceway to feed through into the panel.


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[u2slow]

Bigger box for sure... like 8x8x4" minimum. Get a nice powder-coated one with a hinged cover. I used a 12x12x4" last time I did this sort of thing.

 

[brric]

Why do you need the box? Just install the NM cables through some 2” PVC.

 

[Jim Port]

NM is not to be used in a raceway or sleeve without the outer sheath.

 

[Terabitdan]

Thanks for your replies.

I want the box to make it look neater, it’s not required but the box seals the conduit, which would be required with just Conduit. If having the box results in having to derate or restricts running the Romex through it than I’d drop the box idea.

There is only a 2x10 joist space, otherwise I’d be looking for a bigger box. An 8x8x4 metal box might fit without impacting the other conduits. I’ll see if that works. For sure a 6x6x4” would work and give more space to work in. I could run the other three conduits into the box and definitely use an 8” box.

I don’t plan on removing the jacket until the romex enters the panel. Just passing them through the box and conduit.


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[seharper]

I do that all the time, it’s one of my favorite tricks. However a few gotchas.

- The box cover screws must remain accessible forever without tools.

- If the conduit is more than 24” long, then the “No More Than Four circuits” rule applies. So, do one of two things:
1) Use a BIG box, and run several parallel conduits. Or
2) Use several smaller boxes - as it works out, a 4-11/16” square box (42 c.i.) has just the right cubic inches to terminate 4 #12 circuits.

- If you use PVC, only one ground wire needs to come down the pipe. If you use EMT conduit, the EMT is the ground path. Pigtail a ground wire to the metal junction box, splice all the NM grounds to it, and they don’t need to come down the pipe.

- Check with your AHJ if he will waive the rule prohibiting shucking the sheath off NM-B cable and sending wires down the conduit pipe. If not, you can choose either of these options:

A) use a really big conduit and send down the NM-B still in sheath. That’ll let you write “NW Bdrm” on the sheath which will be helpful to others. Never cram cable in conduit; if it doesn’t go down easily the pipe is too small, but 2” is more than plenty for 5x #12 NM-B. Or

B) Inside the junction box, splice to THHN wires, and run the THHN down the pipe. That’s what I prefer to do. Splicing is no big deal if it’s done correctly (e.g. wire-nut survives a pull-test without tape).
- Note that this will allow you to use MUCH smaller pipe - 3/4” in fact. (You could use 1/2” if there were <=9 wires). That’s nice because boxes with 3/4” knockouts are readily available.

Honestly given that the vast majority of your knockouts are blocked by studs and the remaining ones are precious, I would use the “conduit to box” strategy *quite a lot*. It is kinda my signature move.

Also, before you get too far along, double check your panel size. Spaces are dirt cheap right now, but painfully expensive later (and if you’re adding a subpanel, I bet I’m not telling you anything you don’t already know). I recommend you finish the project with the panel less than half full, with zero double-stuff breakers (twin, duplex etc.) used. If a bump to 30 or 40 is called for, now’s the time!!

You won’t be able to use double-stuff breakers going forward, because of current and emerging AFCI requirements on most 120V circuits and GFCI requirements on 240V circuits. The 240V GFCIs can only be breakers. AFCIs can only be breakers: You can’t put an AFCI at the first receptacle unless the run to the first recep is EMT metal conduit, and remember the part where I suggested EMT? Haha, and there’s a large box with room for a 2-gang mud ring that could take 2 AFCI receps!

 

[Datawise]

I have used that approach many times. The trick is to have a very large box to make connections in.

Here is an older install, but same approach

Cheers
John

 

[Terabitdan]

Thanks for the post John. That looks really nice. For the top one, how did you madly derating? It looks like that conduit is longer than 24”.


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[Datawise]

I don't think it is that long, but even if you derate, most of the circuits are still above the breaker value on most sizes of standard wire.

Here is another angle

Cheers
John

 

[Missouri Bound]

Can you terminate the cables in your "breakout box" and run THNN from there?

 

[Terabitdan]

That looks really nice John.


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[Terabitdan]

Can you terminate the cables in your "breakout box" and run THNN from there?

Yes, once you do all the grounds have to be joined together in the box, so probably a small ground bar and a single ground wire or use metal conduit for the equipment grounding to the panel.

But them my OCD kicks in and I’m thinking of connector strips for the connections, labels on each wire... All to use a smaller conduit. Seems like more work than it’s worth to me. Others did it that way and it looked great.


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[Missouri Bound]

The only thing that matters is that you certainly can do it.
Whatever finesse your OCD pushes you is up to you.
Your plan is good and certainly will work.
How neat you want to make it is a signature of your own work.:thumbsup:

 

[Terabitdan]

Thanks to all who responded for your input. Here is what I ended up doing.

The 2” on the right side of the panel is for the 2-2-2-4 SER, the other two are for the circuits through the 8x8x4 box.

The Romex and MC you see I’m moving to the other side of the joist bay.


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[Datawise]

It looks like you had to mix an match some parts together... not sure why you did not go straight up with the conduits into the box?

Not sure why the locknuts are on the outside (between the connector and the panel) on the two outside conduits. I am guessing you lost a bunch of KO when you cut the hole for the bigger pipe?

Cheers
John

 

[Oldmaster]

Personally if it's all going to be covered I don't go through all the conduit and j box stuff. Creating splices just doesn't make sense to me.

 

[Jim Port]

Personally if it's all going to be covered I don't go through all the conduit and j box stuff. Creating splices just doesn't make sense to me.

Agree, so much unnecessary work.

 

[surferdude2]

I never did anything like that but have seen times that I wished that someone else had. lain:

I did commercial work and always ran some 3/4" spares on new job rough-ins to the area above the drop ceiling just out of professional courtesy. That is, when time permitted and the KO's were available.

Years later when doing remodels on our old jobs, those spares made remodeling less miserable, not fun or easy, just less miserable. :sad: