ECN Forum Forums Code Related Discussion NEC & other Code issues Electrical Panel In One Hour Rated Wall

Rodger
Do you have a reference for two layers of 5/8 on one side of the studs being identified in an UL or ICC assembly?

Larry, I'll see what I can find today.

Roger

Sandsnow, the UL "Fire Resistance Directory", Volume 1, contains a very large number of common construction methods, and their respective fire ratings.
Unfortunately, this book has no index, so you must plow through it until you find something similar.

The design UL designates as "U432" is a simple wall, faced with gypsum board on both sides, and supported by steel studs 24" on center. The cavities are filled with fiberglass insulation. Even theough the gypsum board is only a single layer of 5/8" on each side, this design has a 1 hr. fire rating.
Design "U 425" is similar, but also contains supplimentary information detailing what must be done to obtain different ratings. Under this design, a double layer (both sides) of 5/8 results in a two hour rating for the wall.

From this, and other designs, it is reasonable to equate a double layer of 5/8" gypsum board, on it's own, as equating an hours' worth of fire resistance at that point.


Now- for our panel installation....as I see it, by creating a lined "pocket" in the wall, you are actually moving the panel "outside" the wall. Even though the panel may sit flush with the face of the wall, the wall actually "goes around" the panel. Conduit going through this "pocket", into the panel, is no different than a pipe exiting through the top plate of the wall, and should be treated in a similar manner.

reno
You describe pretty much how the installation of a panelboard in a fire resistive wall was arrived at and justified by numerous jurisdictions.
No test data to back it up. Check out design A202 for ceilings. The luminaires are identified and so are the protection methods. A fire resistive wall assembly would include the panelboard if it was evaluated with it installed.
So why isn't a panelboard shown in the wall assemblies?? Simple. No one has ever asked that it be evaluated or they did and it didn't pass.

Sandsnow, I'm not sure what you are referring to. Design A202 meerly says "UL listed type fixtures"...not any particular fixture, or specially rated fixture. It then follows that the fixtures are not to ocupy more than 24% of the ceiling. Nor are the fixtures wrapped in gypsum.

Your analogy is flawed. Even if it were to be applied....we would be left with "UL listed panels" taking up no more than 24% of the wall.

I have performed numerous ANSI fire tests of building assemblies. I have seen numerous variations of standard assemblies compared to the basic assembly. There is simply no basis to your assertion that either the tests were never done, or that they were, and failed.

For example, while I have not seen fire-rated walls evaluated with panels in them- I have seen the tests done with ATM machines poking through. Since ATM machines contain "fire safes", there is some basis to condsider them as analogous to a panel wrapped in gypsum. In those particular tests, the firewall retained its' integrity.

I think it is safe to assume, after more than a century of systematic testing of firewalls, that were there a problem with "wrapped" panels in firewalls, it would have been documented by now.

I have to disagree. I have looked through many of the descriptions of tested assemblies on the UL web site and in the Gypsum Association's Fire Resistance Design Manual. I can find nothing to support your statement. All of the desgins show the placement of the various elements of the assembly and event get into details such as how the joints are to be staggered on oposite sides of the wall.

This statement from UL is informative (It is on the page you linked. Scroll down to part II General):


From this I gather that rated assemblies are like listed equipment. If you modify them, you no longer have the same thing that was tested. It is not the two layers of sheetrock that give the assembly its rating, but rather, the assembly as a whole. The quote also points out that the stability of the structural members supporting the assembly must last at least until the end of the rating time. If both layers of sheetrock are moved to one face, a fire from the opposite side will immediately begin to degrade the stability of the studs. Such an assembly would certainly not perform as well as the originaly tested assembly.

Having said all of this, I do believe that placing a typical flush mounted panel in a rated wall by "five siding" it, is a commonly accepted practice, and is a modification of a rated assembly that could be allowed by the AHJ, based on the belief that it will not have an adverse effect on the performance of the assembly.

As I pointed out in my previous post, there are rated walls used for specific purposes in which the code specifically prohibits penetrations. In these cases, I feel that the panel installation would not be acceptable. I only mentioned this, because the OP was a general question about placing panels in rated walls, and I wanted to bring out this factor that would effect the answer to that question in some scenarios.


[This message has been edited by eprice (edited 03-07-2006).]

Eprice and Larry, you are correct that it is the assembly as a whole, and I agree that my statement is not backed up by any specific design.

However, the thickness of the membrane is what defines the rating of the protection, for an example, see wall type U424, although it is an exterior wall the protection is described as "Wallboard Protection on Interior Side of Wall" and list the layers needed to provide the required protection for the rating.

Eprice, I think this is the link you were posting.

Roger

Roger,

U424 actually supports my argument. If you look at the design sheet, it tells you that it is tested for exposure to fire from the interior face only. That assembly does not have a fire rating for exterior exposure and could only be used in those cases where the code only requires a rating for fire exposure from the interior face. Where the distance to a property line is greater than 5 feet, IBC section 704.5 only requires a fire rating for exposure from the inside. Those are the cases where U424 could be used.

Eprice, I agree. My point is that two layers of 1/2" sheetrock (in this case) on the interior provides a one hour barrier from the other side of the membrane.

I do agree that if the protective membrane is only on one side of the wall, the structural components of the wall are not protected and in turn would compromise the whole assembly.

Roger

reno
the installation of the luminaires in the assembly is a modification to the assembly just like the installation of the panelboard. The difference is in this case there is a provision for the installation of the luminaires.

"There is simply no basis to your assertion that either the tests were never done, or that they were, and failed."
What other possibility is there?? I ve not inquired as to why the panelboard is not identified in the assembly. I have asked about other items. The answer is always it s never been submitted or it can't pass the test.

"I think it is safe to assume, after more than a century of systematic testing of firewalls, that were there a problem with "wrapped" panels in firewalls, it would have been documented by now."
I would think that if it had been tested with the panelboard in the wall and found acceptable, it would be mentioned in the assembly.

"For example, while I have not seen fire-rated walls evaluated with panels in them- I have seen the tests done with ATM machines poking through. Since ATM machines contain "fire safes", there is some basis to condsider them as analogous to a panel wrapped in gypsum. In those particular tests, the firewall retained its' integrity."
That is the start of some basis to accept the panel in an assembly. was the steiner tunnel test where they heat it up and then hit it with the hose when they take it out? Is there any documentation as far as the results of this test?

Here is what the UL guide info is on design modification:

Design Modifications
Careful consideration needs to be given to alterations or modifications of the fire resistance assemblies.

When field issues arise, it is recommended the first contact for assistance be the technical service staff provided by the product manufacturer noted for the design. Users of fire resistance assemblies are advised to consult the general Guide Information for each product category and each group of assemblies. The Guide Information includes specifics concerning alternate materials and alternate methods of construction.

My opinion is that the panelboard wrap would pass if it were tested, but am in no way a qualified expert to make that assertion.