That's darn interesting. I have to admit, having never personally witnessed the adverse effects of bundling Romex, and having seen it ignored by almost every local "authority" in residential electrical construction, I was darn skeptical about what threat bunlding posed.
Obviously, the bundling does have a serious impact on heat generation.
However, I would have liked the study to address several things: What was the average temperature rise for a single cable carrying the same load as identical bundled cables?
And speaking from personal experience I can say that in a lot of resi. construction cables are regularly bundled for distances far in excess of 24". They may not be packed together in a hole and fire-stopped, so their is certainly more heat dissipation, but by how much? What happens when that same bundle is covered with ten inches of blow-in fiberglass?
I think I'll be a lot more cautious about how I route cables now after seeing this.
You know, John, I think there's a lot of factors involved, too... I mean... South facing walls without shade in Las Vegas are going to get a lot hotter than a north facing wall in colder places of the county.
OT, a little, we sometimes balk at local code, but I think that's exactly why local codes should exist. Local needs might be complete overkill for other parts of the country.
Used to be that inspectors here required only one cable per hole, but in the last few years they realized that this turned the framing into swiss cheese, and now allow two only. (Allowing two 12/2/2's) In the guiese of not exceeding 9 current carrying, as you would in conduit, same for stacker and other bundles. Taking a large bundle of cables, like some would above a panel into a single connector isnt allowed for these same reasons.
That said, if I go a few cities over, where bundling is ignored, you can tell the difference. You really can feel the difference in warmth in the bundles. And on occassion see a slight discoloration of romex sheathes in stuff installed around ten years ago.
Mark Heller "Well - I oughta....." -Jackie Gleason