Big generators

So, today I’m doing a very big diesel generator plant, as standby power for a hospital. I’m required to put in day tanks, to have 2 hours of run time for each of the generators. Each generator uses 150 gallons an hour, and so, for the 4 generators, I need 4 tanks, each 300 gallons or larger.

This means that I need 1200 gallons of fuel (actually, #2 fuel oil, which is a “combustible liquid” under the code) inside my building.

Reading the IBC, Table 307.1(1), I realize, that even with sprinklers, I am only allowed 480 gallons per control area (120 x 2 x 2) but note i tells me that I can only have 660 gallons total inside of the building.

What gives?

Based on a phone call for code interpretation, note i is an “exception” rather than a rule. IE: it’s supposed to show you that if you have more than 660 gallons, you are required to rate the room that the fuel is in.  (I believe that the implication is that you can have 660 gallons in a control area, and keep it as base occupancy, but I haven’t gotten confirmation on this & my AHJ disagreed with me.)

The jury is out as to if this also means that the fuel room becomes an H3 occupancy or not. (In my case, the AHJ required that it be H3).

Code commentary points you to NFPA 31, which covers oil burning equipment, however, this is not correct for generators, as they do not “burn” oil per-se, but rather you use NFPA 37 – which is for Stationary Combustion Engines.

NFPA 101 – Life Safety Code points you towards NFPA 30, which limits you to 480 gal, like the IBC. However, NFPA 30 in 1.5.4(7) indicates that compliance with NFPA 30 or 37 is deemed equivelent with compliance with NFPA 30.

NFPA 37 allows 1320 gallons in a 1 hour rated room.

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