Electrical Penetrations of Firewalls

[RichEng]

Hello,

I'm working on designing service entrances for an apartment building that has a firewall in it. The initial drawings I got showed two service entrances, one on each side of the building. At that point the apartments were divided up 50/50. My question is, do I have to divide up the service entrances in such a way that they each feed their own set of apartments on each side of the firewall? If this is the case, they will not necessarily divide up 'neatly 50/50' Is this a code requirement? Good practice? Anybody ever heard of this?


Thanks

 

[bphgravity]

Does the rated wall meet the minium rating to consider the structure as two separate buildings?

 

[RichEng]

That I do not know. In the architects drawings the wall is labeled as 2-hour fire rated.

 

[boater bill]

You would need a 4 hour fire wall to be considered seperate buildings.

No biggie going through a 2 hour wall, just use the appropriate UL detail.

 

[bphgravity]

You would need a 4 hour fire wall to be considered seperate buildings.

Not necessarily. Per 705.1 of the IBC, each portion of the building separated by walls meeting the minimum ratings in Table 705.4 SHALL be considered a separate building.

The OP is refering to apartments, so I am assuming Group R-2. Per the table, the required separation need only be 3 hrs, or two hours if the (a) note is met.

Its possible 230.3 of the NEC will come into paly. Regardless, you really don't want unnecessary penetrations through rated walls, if it can be avoided.