The Code panel doesn't understand the physics involved.
I assure you that that is not the case. Without substantiation, this proposal would not have been accepted.
This was a panel proposal 7-150a. The substantiation was:
Code-Making Panel 6 Rejected Proposal 6-31 to add the proposed text to 310.15(B)(2)(a) and provided the following Panel statement:
"The Panel agrees with the intent of the Proposal, however, this material is more appropriately addressed in 334.80 since the Proposal only applies to one type of cable, and Code-Making Panel 6 covers all wiring methods. Therefore, Code-Making Panel 6 has forwarded this Proposal to Code-Making Panel 7 for action."
The substantiation provided by the submitter, Travis Lindsey, of Proposal 6-31 was:
"Recent experimentation shows the possibility of dangerous conditions when loaded circuits are brought into close proximity to each other inside a fire- or draft-stop, where the ability to dissipate heat is extremely limited. Cable temperatures well in excess of their 90Â°C rating were encountered, with no overcurrent protection present for these conditions. Results indicate that immediate adjustments should be made to the NEC to apply at least to the specific case represented by the experiment. Such a proposal is being made, with a supplemental report offered as technical support."
This was accepted by panel 6 by a vote of 15 - 0.
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Charlie Eldridge, Indianapolis, Utility Power Guy