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Emergency generator building - fire rating and related questions

formdb

Sawhorse
Joined
Mar 29, 2018
Messages
34
Location
California
We're helping a municipality with updating their emergency generators for multiple well sites. The municipality would like to construct a fully enclosed building, in which a permanent generator will be installed.

Here are a few facts/points of possible interest:

- Project is located in California.
- The building will be about 700 SF total.
- The building will be located essentially out in the middle of a field near some well equipment. 25ft from the nearest building, which houses chlorination equipment but is not occupied. So it appears we would be in compliance with the separation requirements of Table 22.4.1.1(b) from NFPA 30.
- The generator will sit on a large diesel sub-base tank. I believe the tank will be around 1,000 gal.
- A mechanical engineer has designed the required venting for the generator.
- There will also be an electrical room with the main switchboard (800A), auto transfer switch, and various other telemetry equipment.

Here are my questions:

- What occupancy classification should I use? I would typically say it should be U occupancy, as it is a generally unoccupied building. But the diesel tank has me thinking I may need to call it an H-2 or H-3, based on the fact that there will be a diesel fuel storage sub-tank. (CBC Table 307.1(1)
- Would the electrical room need to have a fire separation from the generator room, or would it be considered an accessory use (same occupancy classification), and therefore no separation required? However, per Table 504.8, adjacent H-2 occupancies are supposed to be separated from each other if sprinklered, or are not even permitted if non-sprinklered. The electrical room itself wouldn't be classified as an H occupancy as far as I can tell.
- Will the building need to be sprinklered? Per CFC 603.3.2.1, it appears so, but I don't know if diesel is considered fuel oil:
1637705878236.png
-
There are lots of requirements for spill control and/or containment, I'm just unclear what triggers those.

Thanks for any help anyone may be able to offer!
 
Last edited:

formdb

Sawhorse
Joined
Mar 29, 2018
Messages
34
Location
California
@mtlogcabin, I'm not familiar with what the implications are there. The building will be a pre-engineered metal building, and the structural design will be done by a structural engineer. Are there other implications I should be aware of?

I'm not sure which bullet point you're referring to that would kick us into Risk Category IV, but I'm assuming it's either the "power-generating stations" line or the "highly toxic materials" line. While it is an emergency backup facility for wells related to wastewater treatment, I don't believe wastewater facilities are themselves considered a Risk Category IV structure. I also don't believe diesel would fall under the definition of a 'highly toxic' substance. What am I overlooking?
 

mtlogcabin

Sawhorse
Joined
Oct 17, 2009
Messages
8,285
Location
Big Sky Country
I agree it would not apply for a wastewater facilities. I was thinking private water purveyor providing potable water (cat III) for a subdivision which is quite common in a rural areas in this state or cat IV for fire suppression systems in rural areas without a public water source.
 

formdb

Sawhorse
Joined
Mar 29, 2018
Messages
34
Location
California
Ah ok, gotcha. Any ideas on occupancy classification? In CBC Table 307.1(1) footnote p, Items 2 and 4 both appear to exempt me from needing to stay below the max quantities listed, as the diesel being stored is in service to 'motorized equipment' and/or a 'fixed appliance' (a generator):

1637735595915.png
The column in Table 307.1(1) where H-2 or H-3 is indicated actually states, "Group When The Maximum Allowable Quantity is Exceeded". Interestingly, per footnote p, I am not exceeding the quantities of the table. Does that mean it is not an H-2 or H-3 occupancy? And if not, what is it?? I would lean toward a U Occupancy. Would this be up to the AHJ to make a determination on?
 

north star

Sawhorse
Joined
Oct 19, 2009
Messages
4,104
& * & * &

formdb,

What type of fuel will the generator use,
...fuel oil or diesel ?......If diesel, then, IMO,
the Occ. Type will be a "U".......An enclosed
generator, transfer switch & other telemetry
equipt. would not fit the description of an
H Occ. Group........Also, no separation of
the electrical switch and the generator,
or sprinkling of the structure would be
required......Essentially, you will have an
un-habitable structure with power
generation and distribution equipment and
a 1,000 gal. Belly Tank........The generator
exhausts will exit the enclosure thru the
exhaust pipe to the atmosphere.


Q1): Will the 800A electrical distribution panel
have sufficient "working clearance" around
it ?

Q2): Will the generator engine and "Belly Tank"
have sufficient access for maintenance,
replacement of parts \ etc. ?

Q3): Will the generator exhausts have any type
of noise dampening \ limiting \ maximum
decibel limits ?

Q4): Are there plans to have 1 or 2 "approved
type" portable fire extinguishers in \ at the
enclosure ?

& * & * &
 

Yikes

Gold Member
Joined
Nov 2, 2009
Messages
1,956
Location
Southern California
I agree that it does not fit the definition of other occupancies, so it meets the definition of a U occupancy, which includes "miscellaneous structures not classified in any specific occupancy".

With a metal building, you are Construction Type II-B, which will probably work for most any other potential occupancy classification anyway (S, F, H...).
My suggestion is to submit for plan check listing it as a Type U occupancy on your title sheet of plans, and then if the building official wants to call it something else, it's a simple clerical backcheck correction.
 
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