I have a home owner who wants his breaker panel on the wall between the garage and the house only. As this is a firewall, I can not find much info in the code on it. Only 300-21. Am I missing something? The way I read it, all I need to do is apply a firestop product around the wire holes. This doesn't seem like enough to me.

sparkie,
i beleive there are different levels of classifications of firewalls, ranging from 1 hr burn ,to a distinctly separate building. what can penatrate, or exist in the same bay follows suit. anyone here have this particular code??

There is a limit to how much total area is allowed to be comprised of openings on one side of a wall in relation to total area of wall space. The ratio escapes me now,(I believe it it 100 sq. in. opening per 10 sq. ft. of wall space) but I'll check when I get home.
Also, remember that back-to-back openings are not allowed in the same stud bay, unless certain guidelines are followed, as well.
I'm sure someone else on this site wil know.

I notice that you mention "on" the wall rather than "in". If you surface mount it, you shouldn't have a problem. Be sure to caulk any penetrations in the wall with an approved fire caulk

sparkie,

This sounds like something that you should check on locally. Fire Codes can vary from place to place. I'd ask the local AHJ to be sure about things.

Bill

f) Membrane Penetrations. Walls may have openings for steel electrical outlet boxes not exceeding 16 square inches in area ,provided the aggregate area of such openings is not more than 100 square inches for any 100 square feet of wall or partition area . Outlet boxes on opposite sides of walls and partitions shall be separated by a horizontal distance of at least 24 inches . Where wall-protective membranes are penetrated by other materials or where larger openings are required than permitted above, the penetrating items shall be:

1. Protected with membrane-penetration fire stops suitable for the methods of penetration.

2. Installed in accordance with the installation instructions of their listing for such use.

EXCEPTION:Penetrations not larger than a 4-inch nominal pipe or 16 square inches in overall cross-sectional area containing noncombustible penetrating items, where the annular space between the penetrating items and the protective membrane being penetrated is filled with a material which will prevent the passage of flame and hot gases sufficient to ignite cotton waste when subjected to U.B.C. Standard No.43-1.Time-temperature fir conditions under a minimum positive pressure differential of 0.01-inc water column at the location of the penetration for the time per

Checking with the AHJ is the best answer because there could be other factors involved like.. is that an acceptable location for the panel.
If it is going in the wall a generally accepted way of maintaining the raiting is a drywall box out. Maintaining required air space between layers. Being a house and probably a 3-1/2" studwall, with a box out it will end up a semi-recessed panel.

We're missing something here guys.

Here is the language out of the 200 IRC. It's almost identical to the lamguage in 1995 CABO.

R309.2 Separation required. The garage shall be separated
from the residence and its attic area by not less than 1/2-inch
(12.7 mm) gypsum board applied to the garage side.Where the
separation is a floor-ceiling assembly, the structure supporting
the separation shall also be protected by not less than 1/2-inch
(12.7 mm) gypsum board or equivalent.

Notice that at no time does the code use the term "firewall" in describing this wall/ceiling.

I thinking that this is not truely a fire all in the truest sense of the definition.

Since only one side is required it would not be a "true" fire wall. (20 minute rating at best)

Nick,
That is the spec. I was referring to above. What publication are you referencing?

The spec that Nick has provided is the one that I've been accustomed to using, although I haven't done much resi work for years.
When we have to flush mount anything larger than a quad recp or double switch, it must be "boxed out" with drywall so that it actually lies in a recess that is outside the firewall's envelope.(usually a big pain). When possible,(unless it will project objectionably into a fire corridor or the like) we surface mount panels and such, and for aesthetic purposes will furr out and drywall around them.

UBC 4304(f)

Your question about the fire wall is a good one. The wall that separates the garage from living space is a "fire rated wall" or "area separation wall". This wall must have a resistance to the spread of fire of from 3/4 hour to 1 hour depending on building code in the area. Electrical equipment, plumbing fixutres, vacuum systems, intercom systems, etc etc. that are mounted "in" the sheetrock that makes up this wall, compromizes the fire rating of the wall itself. Testing of these walls is done by many labratories around the country such as U/L, ETL and many private testing facilities including Gypsum Association to determine how many "holes" can you put in the sheetrock and still maintain the resistance rating. Holes can be in the form of plastic boxes, metal switch boxes, etc. The plastic boxes should have a fire rating embossed in the back of the box signifying this box has been tested for a 2 hour wall for example. If the box is not listed for a fire rated wall is should not be installed. Also the separation of these boxes is considered in the "listing" of these boxes - only one box in a bay or no back to back boxes can be installed and only so many square inches of "box space" per so many sq. ft. of wall space. Metal boxes on the other hand are tested "in kind" and the restriction for placement of these boxes are generally restricted because each metal box does not have to be tested individually as does the plastic version. You may find the restriction for the metal boxes is more severe than the plastic only because the plastic types have been indivually tested and each has its own listing for fire resistance. Also the metal boxes can be used in 4 hour walls and plastic cannot.
So much for the holes in the wall and the plastic switch boxes penetrating the walls. There are "no" fire rated circuit breaker panels manufactured. I have researched this particular item and have found that there is only one cabinet box that is manufactured with a fire rating and this is for a fire estinguisher.
If you mount a flush mount panel board "in" the wall, removing sheetrock to do so, you are compromixing the integrity of the fire rated wall assembly. You may not get a violation from the electrical inspector or the building inspector because from what I have seen in the industry no one writes violations on suct things. Some architects do not make an issue of this because the flush mount panel looks better than surface mounted panels.
You should mount the panel on the surface of the sheet rock or build what is called a 5 sided box with sheet rock - the same type used for the wall - in the cavity where the flush mount panel will be placed.

This subject is definetly one that hase been ignored in the electrical industry and your question has opened a door - possibly.
This same issue comes up with "fire rated separation" walls between tennants in commercial buildings - how many flush mount panels have you seen in these walls?