# Diesel generator on high-rise roof (in penthouse)



## beach (Jan 19, 2012)

I'm checking some plans for a proposed generator changeout on a high-rise roof (penthouse). The applicant proposes to remove a 140KW natural gas fueled generator and install a 250KW diesel fueled generator, new transfer switch, etc. They show 267 gallons of fuel located in a belly tank, CFC Section 604.2.14.1.1 requires an on-premises fuel supply, sufficient for not less than a 6-hour full-demand operation of the system. HOWEVER, since this is a high-rise that requires a level 1 generator and we are in seismic design catagory C, NFPA 110 5.1.2 requires a 96 hour minimum fuel supply. By my calculations, the generator would require a minimum of approx. 2,100 gallons of fuel (which would weigh approx. 15,000 pounds). This is approx. because I don't have the manufacturer specs. (another correction...)

Since this is my first high-rise roof-top generator, I want to make sure I got this right...... I have other corrections, but this one will surely not allow what they want to do due to the fuel quantity.

1. Does my correction sound correct (am I missing something)?

2. IF they were allowed, for some reason, to only use the 267 gallons as noted.... how can they re-fuel it on the roof per code?

I'm guessing that is why the existing generator is natural gas?

Any opinions are welcome, Thanks in advance!


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## cda (Jan 19, 2012)

How they going to get it up there?? Fly it

Would calif allow the fuel to be pumped up from a ground tank?

Does calif allow them on the roof in new construction??

Sounds like I would require a very technical report on this one

Not a high rise person


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## beach (Jan 19, 2012)

Yes, helicopter.....

I'm not sure if they can pump 19 stories (well... maybe... over 85 psi to the top? Probably more since it's diesel.......) and I'm not sure if I want them too

There is no code that i'm aware of that prevents it.

Yeah..... it's new to me too, I usually see them in a basement!


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## cda (Jan 19, 2012)

The only thing about pumping it besides if it can get there, is protecting the pipe seismically

I think I would go with a technical support

Also ask some adjoining ahj about how they handle high rises


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## cda (Jan 19, 2012)

Check nfpa 37??

http://38.106.4.187/index.aspx?page=1091


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## Coug Dad (Jan 20, 2012)

cda said:
			
		

> How they going to get it up there?? Fly it


You take it up the service elevator in 55 gallon drums.  I unfortunately know of a couple of buildings where they do this.


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## permitguy (Jan 20, 2012)

> You take it up the service elevator in 55 gallon drums. I unfortunately know of a couple of buildings where they do this.


We have one that does the same, but it only has the belly tank.  Pure stupidity if you ask me (and the building engineer), but I'm not aware of anything that makes it non-compliant.


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## north star (Jan 20, 2012)

=

Is the proposed new generator for the penthouse only, or the whole building?

*=*


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## beach (Jan 20, 2012)

Thanks for the replies!

I think it will probably be a moot point when they find out they need over 2,000 gallons for a 96 hour run time due to the seismic design category. Probably not the best idea to stay with natural gas due to pipe breakage during a seismic event, but I don't think they have a choice.

Northstar: it's for the whole building


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## north star (Jan 20, 2012)

*=*



Thanks for the clarification!

*=*


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## That Inspector Guy (Jan 20, 2012)

If they have to do the 2K of fuel in order to comply, you should get the Fire Code Official/Fire Marshal/Fire Dept involved in the planning on that one- Diesel is only a combustible but I am sure they would still want to know about 2K of fuel on the top of a high rise. Also better get an engineers approval for the weight of the gen set plus the 2K of fuel.....as the others stated- get a techno report on EVERYTHING!!!

Any reason they can't do the basement?


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## beach (Jan 20, 2012)

I am the fire code official, the surrounding buildings have generators in the basement, this one was originally built with the generator in the penthouse, not sure why...... Definitely need structural calcs, etc. for the building dept. if they choose to put 2,000 gallons of diesel on the roof, among other things. I'm thinking they will probably stick with natural gas. We'll see what they come back with...


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## gbhammer (Jan 20, 2012)

beach said:
			
		

> I am the fire code official, the surrounding buildings have generators in the basement, this one was originally built with the generator in the penthouse, not sure why...... Definitely need structural calcs, etc. for the building dept. if they choose to put 2,000 gallons of diesel on the roof, among other things. I'm thinking they will probably stick with natural gas. We'll see what they come back with...


The FCO's around here never think for a second about things like dead loads. It's nice to see that you do beach. I wish all the fire marshals around my area would get on this forum. I'd have to go a bit more incognito.


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## beach (Jan 20, 2012)

Thanks GB! I try to give the applicant or other departments as much information (corrections....) as I can, whether it's a building dept. or fire dept. issue, just in case it might get missed....... so it's not a surprise later on.

I hate seeing "field verify" on plans.....


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## AegisFPE (Jan 20, 2012)

The 96 hours may see some pushback if it's based on 100% of the generator load. Consider that the shafts served by pressurization equipment are only rated for 2-hours, so the associated equipment may not need to be supported beyond 2 hours; smoke control systems need only operate for 20 minutes. Similarly, NFPA 20 specs a run time for the fire pump. Therefore, the full demand of these emergency systems may be limited to 2 hours (anticipating that the building is evacuated after such an incident such that the additional generator run-time is not needed, or the fire occurs at the 94th hour).

Sacramento had (been a few years since I did a highrise there) a limit for the number of stories above grade the generator could be; 2 or 3 as I recall.


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## CindyOu (Nov 24, 2017)

Get some helps of 250KW diesel generator technical parameters.


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