Opinions

[rocco]

I had discussed this with my brother at the time (he's the contractor) and we agreed that the code enforcement officer may not be all-knowing.

But his concern was that, although he knows a lot of electricians, he could not rely on any of them to provide a definitive answer. He feels that all they know is what the code-enforcement officers like to see, and not what the code really requires.

 

[upstatemike]

To me it would be a bigger concern to put a J box at the top of the conduit to transition from romex to TX and then seal the splice away behind a sheetrock ceiling.

Is it even legal to have a splice in a place that is not accessible? I also question the validity if heat buildup in conduit being a concern. If you run a 12/2 at its rated capacity of 20 amps I don't think it will generate enough heat impact the insulation. TX has a higher temp rating but that is because you can run a lot more of them in a single conduit.

 

[Digger]

Rocco,

I agree you have to do what the code officer wants.... right or wrong unless you can politely point out an oversight to them. A couple of months back I posted a comment never to pee on the code officers corn flakes for just this reason. They can really make you jump through hoops if they want you to.

Upstatemike,

You are correct you cant have an inaccessible splice. The intent of the code officer is to protect the wiring from mechanical abuse which I agree with. You could put a surface box at the top of the wall and transition to conduit. Its not a huge expense but it is a lot of work.

Odds are nothing will ever happen. You would have to pull a significnat load through the wiring to have it heat enough to degrade the insulation I would presume, however, I am not an expert.

 

[rocco]

Well, I got curious and did some calculations. I determined that the heat dissipation from 20 amps traveling through 6.7 feet of 12/2, round-trip, would generate 8.7 watts of heat at 77 degrees F, and 10.0 watts at 149 degrees F.

But the cable is surrounded by furring, concrete block, sheet-rock and insulation. There is no air space in the wall. I suspect that the conduit will not be a factor in preventing the heat to escape, and may even help bring the heat up through the fire-break and into the ceiling rafters, where there is air-space.

 

[Digger]

I dont think the concern is that the wire will be so hot it will melt away the insulation or cause a fire to ignite. I think (notice the word think) that the concern is that the insulation will degrade over time by the increased temperature from the wire enclosed in the conduit.

Again I doubt that there would be a real hazard especially if there is intermintant duty cycle.