I've got a new 100a panel mounted on an outside wall - 3' below where the roof intersects the wall's top plate - and am planning to run a 6/3 romex feed to an interior 60a sub panel (~25' of wire. 6/3 is good for 55a but code lets you round up to the next breaker size).

I'd like to use 3' of sch40 1-1/2" pvc conduit to protect the romex on the outside of the house... running it from the hub on top of the panel, up and into the attic just above the top plate of the wall. I'm using a bigger than necessary conduit so in the future I can squeeze in two 12/2s and still satisfy fill requirements.

My question is am I required to use a conduit body to enter the attic, or can I just drill a hole through the siding and pop a 90 degree elbow into the attic? (clearance is tight and a conduit body will hit the underside of the roof before I can get it into the attic).

See sketch:

 

Welcome to the forums!

You are not required to use a conduit body, a 90 degree elbow is OK. Make sure the hub on the top doesn't just feed into the meter part of the combo panel.

 

Hey thanks for the fast reply! There are two hubs on top of the panel - it's a side by side... so one hub is above the meter section and the other one I'm going to use is over the breaker section.

 

You cannot use NM outside, even if sleeved in conduit. You will need UF or even better, individual conductors in a completely conduit system.

 

Aw crap, pcboss thanks for pointing that out. I forgot you can't use NM in wet or damp locations!!

There are knockouts in the back of the panel (in the breaker section)... the panel is outside, so two more questions:

1. if I run the NM in the interior of the wall and out into the back of the panel, does that still count as running NM outside?

2. would i have to use conduit in the wall cavity to protect the cable, and would pvc be ok for that?

If that's a bad idea I'll just do THHN and use the cable I already bought for something else

 

A cable into the back of the box should be fine. Unless subject to damage a sleeve should not be needed.

 

You mentioned running more 12's in the future,why not run the PVC from the meter into the attic into a "J" box and make your transitions up there,although an attic may not be the ideal place to work.
Just a thought.

 

Thanks Geochurchi and pcboss for the advice!

Geochurchi, you're right on... I was looking at mounting a pull box or big jbox in the attic and running conduit to it, running thhn to the box, and running romex from the box to the other circuits.

If I did that then I'd just continue the conduit down to the sub and feed it with thhn like pcboss said.

It's a bit of a pain since any equipment grounding conductors run in the conduit have to be bonded to the jbox, to any romex egc in the jbox, and then go on to the grounding bus bar in the sub (and kept seperate from the neutral/grounded conductor of course). Maybe i'll use a grounding bar.

 

True, but you need only one EGC in the conduit, sized based on your largest circuit. (Which I think is 10ga for a 60A circuit - but someone should double-check that). So you only need that one 10g bare or green wire for a ground, bond it to the box, and wire-nut it to your other circuits too. A few less wires to pull!

 

Ah right, thanks Zorfdt... I forgot I could do that. Per NEC 250-122 I can use one egc for all the circuits as long as it's properly sized

For sizing, I initially thought I had to add up all the overcurrent devices for the conduit run (60+20+20) and use an egc for 100A, but after re-reading the code it seems I size the egc according to the largest overcurrent device for the 3 circuits, which is 60A. And according to table 250-122 I'd use 10awg... which is exactly what you said. Thanks again!

 

That is correct. .....................

 

As you mentioned, install a ground bar inside the "J" box much cleaner than trying to use wirenuts.