[hotrodjohn71]

I have a room addition I'd idle to run power to. I'd like to additional 2 20A breakers to my exterior box which would send power to the new room via 2 12/2 romex wires. The box doesn't seem to have any knockouts. Can I cut a hole in the top and attach a plastic conduit to the eve's similar to the Exhisting on the right? The conduit on the right already has maximum wires. The metal conduit on the left is power in from the roof.
Thanks

 

[Oldmaster]

If you put a hole in the top you will need need to install a Myers hub. This is a hub with an O ring that keeps the water out.

 

[Jim Port]

NM cannot be used outside, even if in conduit.

 

[hotrodjohn71]

Thanks. My apologies for the grammatical errors. I wasn't able to edit.

 

[Wiredindallas]

To further explain a Meyers hub, you need a threaded collar that is attached to the panel with a gasket. You can then use a threaded connector (male adapter) that will be watertight itself. It doesn't look like the existing PVC on the right is compliant unless there is an o ring washer on the adapter.

 

[hotrodjohn71]

Thank you and thanks Jim for that info. Am I permitted to just shave off the yellow protective outter coat on my romex for that short (2 1/2 foot run) through the conduit from the eve to the pannel?
If not, which wire is preferable, solid or stranded wire.
thank you

 

[Oldmaster]

The issue is the wire in RX
It is not approved for wet locations.

 

[Wiredindallas]

If you want to follow the code to the letter, use UF wire to the 1st junction.

 

[Oso954]

I'd run THWN.
Between the very short run and being able to use smaller size conduit, it's probably less expensive than using UF in conduit.

IMO, it would be an easier installation.

 

[hotrodjohn71]

Thanks guys. One last question. What size conduit would I need for six 12GA THWN wires if I go that route? Thanks a million.

 

[Oldmaster]

I'd recommend 3/4 in.

 

[seharper]

OP has the right idea to go THHN- whoops I mean THWN-2. (same stuff; it's dual labeled). However you only need 1 ground wire - circuits can share it.

You can calculate allowable conduit fill here. 5-6 wires is fine in any conduit made, but 3/4" conduit will pull easier (and install harder lol).

If you want to follow the code to the letter, use UF wire to the 1st junction.

Yes, but UF is quite flat, and flat cable requires excessively large conduit. You must compute conduit fill like it's a round wire of the large dimension (because it twists). And with 2 "wires" in conduit, you are only allowed 30% fill. So for dual 12/2UF, you need (are you sitting down) 1-1/4" conduit. Try it yourself in the conduit fill calc: 12/2 UF is .463" across.

 

[hotrodjohn71]

Thank you for the advice. Especially about only needing one ground wire so I'd only be running 2 whites, 2 blacks and one ground (THWN) in my 3/4" Pvc conduit for the 2 circuts.

 

[hotrodjohn71]

One more question. Please see the image I found on the net similar to my situation.
In my case, where the Pvc conduit will enter the attic, there is very little room to work with a junction box. Would it be acceptable to run the attic enclosed conduit over several joists (which run perpendicular ) to be able to locate my junction box in a more accessible spot?

 

[Jim Port]

You could even extend the conduit further past the elbow.

 

[hotrodjohn71]

Thanks Jim. Do I need to run the conduit on a strip of wood across the joists?