ROMEX in Conduit

[L+10]

1. Can I run 12/2 ROMEX in 3/4" PVC conduit in a detached garage? Am I wasting $$ wiring the outlets this way?

2. Since this is a pole barn, can I run the ROMEX down the girts right next to each pole without conduit; mount the outlets on the face of pole ~ 4' off the ground and then just use conduit to protect the ROMEX from the girt to the outlet box? Has anybody done this?

 

[LoneGunman]

You are just using the PVC as a sleeve to physically protect the wire on the vertical drops to the receptacles, right? If so, it's done all the time but usually with EMT. There is an argument that it is not a code compliant installation if you strip the outer insulation off the romex, which is funny because they make connectors just for that use.

If you can run the romex down the side where it is not subject to physical damage then the conduit is not needed.

 

[usmc_noma]

what's wrong with doing it that way? i did it this way. i had extra romex and i wanted to have outlets on a finished wall that i didn't have access to get under the drywall so i just ran emt down the wall with the romex inside. took me awhile with measurements but i'm finally finished. looks good to me. personally i'd use emt than pvc but it shouldn't matter as long as there's no point where the pvc could get damaged.

 

[Charles (in GA)]

Chapter nine of the NEC has methods to calculate the area of sheathed cables (such as Romex) in order to determine the fill requirements of conduit, so there is nothing wrong with running romex in conduit, so long as you properly figure the area and fill requirements.

Take a caliper, measure the romex across the widest part of the ellipse (longest cross section dimension), assume this is the diameter of a circle and convert this measurement to the area of a circle (pi times r squared ? I think) armed with this number, and knowing that a multi-conductor cable (romex) or cord, with two or more conductors is treated as a single conductor for purposes of fill (53% fill for a single conductor, one Romex; or 31% for two conductors or two romex runs; or 40% for three or more conductors or three or more romex runs) and knowing that Article 352 rigid PVC has the following fill numbers, you can determine if the romex will legally fit in the conduit.

100% of internal area of 3/4 PVC is .508 inches square
53% is .269 inches square
31% is .157 inches square
40% is .203 inches square

and oh yes, if the run is less than 24 inches it is considered a ****** and the fill is 60% allowed or .305 inches square.

Charles

 

[Torque1st]

You can also use the width and thickness of the Romex and treat it as a rectangle LxW=A to more closely approximate the area.

 

[Charles (in GA)]

You can also use the width and thickness of the Romex and treat it as a rectangle LxW=A to more closely approximate the area.

Is that somewhere in the code? Or have I missed something somewhere else in the code? Lord knows, it wouldn't be the first time I was wrong on something.

The only reference I've found to calculating the area of a sheathed cable is Chapter 9, Table 1 notes (which is the first page of Chapter 9) and it says......... "(9) A multiconductor cable or flexible cord of two or more conductors shall be treated as a single conductor for calculating percentage conduit fill area. For cables that have elliptical cross sections, the cross-sectional area calculation shall be based on using the major diameter of the ellipse as a circle diameter."

I interpreted that to mean that you treat the ellipse as if it were a circle.

Charles

 

[Torque1st]

Well, it is from Geometry which is older than the code. Since Romex could very loosely be described as an ellipse that may be a good interpretation and may be what they mean. I do not know their intention. For cables like Romex LxW would more closely approximate the area.

 

[Aceman]

Conduit fill rules don't apply here.

See Ch. 9, note to tables (2)

 

[Charles (in GA)]

Conduit fill rules don't apply here.

See Ch. 9, note to tables (2)

I guess a "complete system" would be a single run of conduit from breaker panelboard to the receptacle boxes.

vs conduit run down the wall just from the header to the receptacle.

Charles

 

[Aceman]

I guess a "complete system" would be a single run of conduit from breaker panelboard to the receptacle boxes.

vs conduit run down the wall just from the header to the receptacle.

Charles

Exactly.