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

Is it allowed in the NEC to install a loadcenter in a one hour fire rated wall? I have been looking thru the NEC and haven't found anything regarding this as of yet. If it is not allowed, could someone provide me with the article number.

This loadcenter is for one of the units in a highrise multifamily residential project that we are doing. All the other units in the building didn't have this concern, however, this one unit does not have any walls that will really accept the loadcenter. Asthetically that is.

Thanks for any help

Dave

Welcome to the forum Dave.

With the exception of some basic wording in 300.21, this is not an NEC issue.

NFPA 221; "Standards for Fire Walls and Fire Barrier Walls" would be helpful.

A UL design would be needed and can be found in the UL Orange books (Fire Resistance Directory) or go to this UL page to start a search, but it can be frustrating unless you know what you're looking for.

The easiest way to do this would be to "five side" the panel with 5/8" sheetrock, this would mean the wall would have to be atleast a 6" deep wall.

Roger

Thanks for the quick reply. I had found that article and only that article in the NEC that pertained to my question. Just wanted to make sure before I went on with this project.

Thank you for the welcome also.

Dave

A panel in a fire wall..a wall that depends upon both facings for its' rating....would most certainly cease to be effective. A common method of dealing with this is to "box in" the panel; that is, surround it with several layers of sheetrock.

The question comes down to "what is the specific wall design?" There are various "Fire Resistance" directories out there that detail different wall types, and their ratings. You would have to find your wall in one of these in order to determine what you need to do.

"But Steel doesn't burn" ....someone is sure to say. True enough, but steel does get hot. For a wall to pass a "fire test," not only must the wall survive, but the side away from the fire is not allowed to get hot either.

I have not found anything in our building code or in the UL direstory for fire resistance that allows for panelboards in fire resistive construction.

Rodger's method of "five siding" is commonly accepted, but is not backed up by any tested assembly I've seen.

If anybody has a UL classified (or equal) assembly for this I would really like to see it.

Larry, by "five siding" the enclosure you are simply contouring the membrane around the enclosure unbroken, so the only concern would be the conduits penetrating through the sides which would need to be sealed properly.

In otherwords, the enclosure could be removed and you would simply have an indentation in the wall that would not compromise the thickness of the overall membrane(s).

With this being said, IMO there really is no need for a designed assembly.

Once we go above a 2 hour wall design things would be different

Roger

As has been said "five siding" enclosures is a commonly accepted approach, however, it is not only the thickness of the membranes, but the the thickness of the space between them that enables a wall to hold up to a test. Depending on the size of the panel, placing it in the wall may cause a localized area where stud support for the sheetrock is spaced farther apart than what was tested by UL. As sandsnow stated, there is no test data that backs up the use of "five siding" to solve these situations

For me, a factor that would weigh in to determining the acceptability of this approach would be, what is the reason the wall is rated? In the IBC for example, some walls, such as stair enclosure walls and exit passageway walls (these are more than just corridors) get special treatment. These are required to have no penetrations except for wiring, ducts, etc., that are needed to serve the enclosure or exit passageway, and that would include both membranes of the wall. I would be very reluctant to allow a panel, even with "five siding", in one of these walls. The wall assemblies were not tested by UL with an indentation. In other rated walls, I would be more inlined to accept the "five siding" approach.

Eprice, if a wall design or code specifically prohibits a panel, outlet, Fire Extingisher Cabinet, or any other item from being installed in a particular wall, then that is a different story as was noted in the last sentence of my post.

We are now moving into other areas from the original question concerning a "one hour wall". In most one hour designs the required double 5/8" sheetrock can be on one side of the wall if desired.

Roger

First of all, nobody can speak for UL except UL itself.

That said, one of the services UL offers is a field review of modified assemblies, where a decision is made as to whether the item continues to meet UL's standards, without requiring additional testing.
The reason for this service is two-fold:
-First, sciensc, and logic, allows us to make such decisions wisely, assuming we have the necessary data; and,
-It is simply not possible to test every possible variation of a wall.

The issue is one of "engineering judgement." An AHJ really doesn't have a leg to stand on if his 'instincts' conflict with the professional judgement of the engineer or architect.

If there's a question, then it is time to make the engineer earn his pay, and have him make the call.

Fire rated walls are engineered assemblies but there are, what amounts to, mastered plans for firewalls. I would be surprised if there isn't a "master" for a wall with a pocket in it big enough for a panel. This can't be the first time it has come up.