310.15(B)(3)(c)

[mbrooke]

Why was this added to the code? Have there been many wire failures? Id imagine very old rubber insulation might but my understanding is that newer THHN is a lot more durable.

 

[infinity]

Shooting from the hip I would guess that there were a minimal amount of failures if any but scientifically I could see where someone would hypothesize that the heat from the roof could affect the conductors. IMO this was more of a solution looking for a problem that didn't really exist. In the 2014 NEC they have eliminated this requirement for XHHW-2 because there was no actual problem with those conductors on rooftops.

 

[ActionDave]

I agree.

There has not been any problems in my fair city.

I really think part of what's going on with some of these senseless code changes is the CMPs need something to do to make them feel important. So many of the safety issues have been taken care of, now they are left with solving problems that might happen, no matter the lack of evidence of a real problem.

 

[mbrooke]

I agree.

There has not been any problems in my fair city.

I really think part of what's going on with some of these senseless code changes is the CMPs need something to do to make them feel important. So many of the safety issues have been taken care of, now they are left with solving problems that might happen, no matter the lack of evidence of a real problem.

I get the same sense with this rule. If anything this is another code change to sell more of something. Bumping a few conductors up in size here and there adds up.