FIRE RATING FOR TRANSFORMER VAULTS OF 5000 VOLTS AND ABOVE

[nonsinusoidal]

A high rise building(condominiums) composed of more than three levels is to be electrically fed by an electric utility. There will be transformer vaults in some of the floor levels. They will be connected by concrete encased vertical raceways. I would like to know what is the minimum Fire Rating for the Transformer Vaults and vertical raceways within the high rise building. Can anyone advice which code in the NFPA or the international building code will have to be followed by the electric utility to accomplished the above mentioned task?

 

[stookeyfpe]

Minimum 3-hour in a high-rise building. Normally a 4-hour separation is required but IBC Chapters 5 and 7 allow a one-hour derating when the building is sprinklered. I'm assuming you are using the 2006 IBC and its height is 420 feet or less above the lowest level of fire department access.

If its 2009 IBC, the derating stops at 420 feet at or below the lowest level of fire department access and the floors are occupied. Above 420 feet, its 4 hours. You'll need to extend those shafts to the electrical equipment rooms as I am unaware of through-penetration fire stop assemblies (but my experience is limited to 3 hours or less).

Good luck.

 

[nonsinusoidal]

I am attaching a drawing of the type of shaft that will be utilized to bring electrical power, within a high rise building, from the electric utility's vault (located outside in the street underground.) The shaft on the drawing can be visualized by the heavy weight of the lines on the drawing. The letters denote the following:

1. "A" a transformer vault (room)built to a minimum 4 hr fire resistance rating

2. "B" is not a transformer room but has a vertical raceway concrete encased conduit system through it connecting the transformer vaults above and below the indicated levels in the attached drawing.

3. "C" Vertical Raceway concrete encased steel conduits built to a minimum 4 hr fire resistance rating

Is the system I have described above and depicted by the attached drawing considered a shaft system under the 2006 IBC? Are the through penetrations by the vertical raceways concrete encased steel conduits in the transformer vaults required to be sealed by a fire-stop sealant?
Please advise as appropriate and thank you in advance

 

[stookeyfpe]

First, thank you for the drawing. Under the 2006 IBC, Section 702.1 defines a shaft as:

An enclosed space extending through one or more stories of a building, connecting vertical openings in successive floors, or floors and roof.

However, looking at your design detail, one could also interpret the vertical raceways as a through penetration:

An opening that passes through an entire assembly.

In the context of the IBC, an assembly is the floor, which must be constructed as a horizontal assembly because of the IBC fire-resistive construction requirements. Because this is a high-rise building, each floor is required to have a 3-hour fire-resistance rating.

In my opinion, I would call the vertical raceways as a through penetration. These penetrations would need to meet the requirements in IBC Section 712.4, which it appears you
are attempting to meet. The only concern I would have is IBC Section 712.4.1, exception 1. It limits the area of the vertical raceways.

I would recommend you contact your plans examiner and get his/her interpretation. Let me know if you need additional assistance.

 

[EEJaime]

nonsinusoidal/stookey,

I believe that if the rating of the shafts is carried continously through the transformer rooms, this in fact creates and defines a shaft. It is precisely for the sake of eliminating the fire stop assemblies at each floor that we would have a fire rated shaft between transformer rooms. If the fire rated assembly was actually penetrated at each floor, and sealed with a UL listed assembly, there would be no need to rate the vertical portions of the electrical risers. That is the argument I have made to AHJ's in the past and there has never been an issue.

Just presenting the electrical point of view.

Regards,
EEJaime

 

[EEJaime]

Gentlemen,

Well, my last statement holds true for lower voltages, I failed to note that this was for voltages greater than 5kV. I should read these things more closely.

Regards,
EEJaime

 

[stookeyfpe]

EEjamie,

I hate posting answers that I spent over an hour figuring out and not getting answers. I saw the 5KV value and felt like the vertical penetration was a through penetration.

The original poster never responded. Do you agree with my interpretation of the NEC? I believe my findings are consistent with the IBC. I would appreciate a EEs opinion. His design was uncommon for me.

Thank you EEjamie for offering your opinion.

stookeyfpe

 

[nonsinusoidal]

Sorry for not providing feed back on my original question. However, I have been doing some research on this subject matter. I just recently was able to get a hold of the international building code material. Thank you for every once's response.