ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat Box
Recent Posts
Lock-down Thread
by gfretwell - 05/08/21 01:39 PM
Do You Travel?
by gfretwell - 05/07/21 07:44 PM
Unemployment Fraud
by gfretwell - 05/07/21 07:28 PM
How's all our Non-US folks doing?
by grich - 05/07/21 06:04 PM
Where is Everyone?
by grich - 05/06/21 05:49 PM
New in the Gallery:
2020 - 2021 Winter Project
Garden 2021
Who's Online Now
0 registered members (), 16 guests, and 17 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
334.80 #98394 11/13/04 10:43 AM
Joined: May 2002
Posts: 1,716
R
Roger Offline OP
Member
Does anyone else see a problem with the wording in the new paragraph of this article?

Where more than two NM cables containing two or more current-carrying conductors are bundled together and pass through wood framing that is to be fire-or draft-stopped using thermal insulation or sealing foam, the allowable ampacity of each conductor shall be adjusted in accordance with Table 310.15(B)(2)(a)

Or maybe the question should be "HUH"?

If the cables meet the definition of being bundled this is already required and why would "thermal insulation or sealing foam"
be singled out?

If we used a fire caulk, would we not need to adjust the ampacity even if the cables were bundled? [Linked Image]


Roger

2017 / 2014 NEC & Related Books and Study Guides
Re: 334.80 #98395 11/13/04 11:17 AM
Joined: Apr 2004
Posts: 201
CharlieE Offline
Member
Roger, I am guessing and not looking at the ROP or ROC. Fire stopping with this foam or insulating material is different from the standard fire calking or other type of intumesce material that expands upon the presence of fire. Under normal conditions, heat will not be dissipated so Panel-7 has accepted the requirement to protect type NM cable irrespective of the length of the bundling. [Linked Image]

- - - - - - - - - - - - - - - - - - - - - - - - - - -
Charlie Eldridge, Indianapolis, Utility Power Guy


Charlie Eldridge, Indianapolis Utility Power Guy
Re: 334.80 #98396 11/13/04 01:33 PM
Joined: Oct 2001
Posts: 597
E
ElectricAL Offline
Member
The more interesting turn of phrase, to me, is draft-stopped.

I take this to mean the sealing that insulators do to minimize air flow through stud cavities by squirting foam into the holes I drill for my NM-B.


Al Hildenbrand
Re: 334.80 #98397 11/13/04 02:33 PM
Joined: Apr 2004
Posts: 201
CharlieE Offline
Member
I don't see the term draft-stopped as minimizing. With foam and thermal insulating material, you are blocking all airflow now and adding heat-retaining material. Therefore, the need for the new rule (this is a guess). [Linked Image]

- - - - - - - - - - - - - - - - - - - - - - - - - - -
Charlie Eldridge, Indianapolis, Utility Power Guy


Charlie Eldridge, Indianapolis Utility Power Guy
Re: 334.80 #98398 11/13/04 07:54 PM
Joined: Oct 2001
Posts: 597
E
ElectricAL Offline
Member
Quote
I don't see the term draft-stopped as minimizing.
Are you suggesting that this Code language is not applicable to the scenario I'm describing? It seems to me that the sealing foam that is squirted into the hole that I drill for my NM-B will stop the draft through that hole. In my experience, the insulator will leave framing irregularities and joints un-stopped. The stud cavity will still draft, but at a lesser level, perhaps a minimized level, after the electrical penetrations are stopped.


Al Hildenbrand
Re: 334.80 #98399 11/13/04 11:44 PM
Joined: Apr 2004
Posts: 201
CharlieE Offline
Member
Some of the fire stopping is done with intumesce material that expands upon the presence of fire. In other words, it does not stop all movement of air until a fire activates the material and it will expand to fill the opening. [Linked Image]

- - - - - - - - - - - - - - - - - - - - - - - - - - -
Charlie Eldridge, Indianapolis, Utility Power Guy


Charlie Eldridge, Indianapolis Utility Power Guy
Re: 334.80 #98400 11/14/04 02:36 PM
Joined: Dec 2003
Posts: 751
E
earlydean Offline
Member
The wording is chosen carefully so that the electrician is not sent to the bundling section, but rather directly to the table. This requires us to derate cables, no matter how short the distance, when they are routed through a fire-or draft-stopped thermal insulation or sealing foam.


Earl
Re: 334.80 #98401 11/15/04 01:08 AM
Joined: Jun 2004
Posts: 92
P
Peter Offline
Member
This is another reason not to adopt the 2005 Code.
The situation is that the Romex cables pass through a 1 1/2" thick stud and the rest of the hole is sealed with foam. It should be emphasized that this is only for a distance of 1 1/2".
Earlier editions of the Code recognized that the copper will conduct away any built-up heat. Thus the permission to bundle for up to 24" without derating.
This section of the Code should not be adopted. The Code panel doesn't understand the physics involved.
~Peter

Re: 334.80 #98402 11/15/04 08:53 AM
Joined: Apr 2004
Posts: 201
CharlieE Offline
Member
Quote
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 90°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. [Linked Image]

- - - - - - - - - - - - - - - - - - - - - - - - - -
Charlie Eldridge, Indianapolis, Utility Power Guy


Charlie Eldridge, Indianapolis Utility Power Guy
Re: 334.80 #98403 11/15/04 09:43 PM
Joined: Feb 2002
Posts: 375
G
George Offline
Member
I believe that Peter is correct and that the submitter, Travis Lindsey, is wrong.

If Mr. Lindsey is correct, a single NM cable also has the problem.

If Mr. Lindsey is correct, we can also look at foam insulated walls and discover that NM cable should never be used in those.

I will continue to do engineering for heat related derating and continue to use "old" code methods.


Featured:

2020 National Electrical Code
2020 National Electrical
Code (NEC)

* * * * * * *

2020 Master Electrician Exam Preparation Combos
2020 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
sparky66wv
sparky66wv
West Virginia
Posts: 2,236
Joined: November 2000
Show All Member Profiles 
Top Posters(30 Days)
Trumpy 15
Admin 8
Popular Topics(Views)
278,691 Are you busy
211,890 Re: Forum
198,941 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.3