Using a campus generator for legally required loads...

[DownRiverGUy]

So fun little design question for you guys...

Working with a University that has a LARGE generator on-campus that they use when the Utility power goes out. The generator can handle all the campus load and will supply power within 60 seconds (a little over 10 seconds really).

We are designing a building that requires Life Safety and Legally Required Standby Loads.

The Life Safety have to go on a small generator on the roof because the Campus Generator will not produce power in time.

BUT is there anything in the code that forbids us from connecting the Legally Required panel directly to the substation of the building? AND what would you consider the "source of power" for the building at that point?

If i'm leaving something out please let me know guys. I have a few engineers butting heads and I'd like some outside input.

Thanks as always!

 

[ron]

What type of loads are you working with?
You must pick up the load in 10 seconds (maybe with batteries), but it doesn't matter if the non-life safety generator plant takes over after 60 seconds and goes the rest of the way.

 

[DownRiverGUy]

Here is the timeline here..



UTILITY POWER CUTS OFF

Within 10 seconds the Generator on the roof kicks in and supplies Life Safety Loads.

Within 60 secounds the Campus Generator kicks in and supplies the Legally Required Standby loads (along with the rest of the loads in the building).

 

[zbang]

While I like the concept, how does it protect against substation or distribution failure (aka "backhoe fade" in the telecom industry)?

 

[charlie b]

I am going to challenge your use of terms here. I need to know if you are using the right language, before I give my answer. There is too much opportunity for confusion, if we don?t use the same words in the same context.

First of all, the phrase ?life safety? appears in article 517, not in 700. You are talking about a university, not a hospital. Does this university have a teaching hospital on campus, and are you working with that building? If not, may I surmise that you are talking not about ?life safety? loads, but rather about ?emergency? loads, such as egress lighting?

Secondly, may I ask what is the nature of the ?legally required standby? loads you are working with? Do they meet the definition of article 701.2?

Finally, I do not understand what you mean by saying you want to connect the legally required panel directly to the substation at the building. Do you have one source of power, such as from the utility, coming into the building, and will that be connected to an automatic transfer switch, with the campus generator being connected to the other side of the transfer switch, and with the legally required loads being powered from a panel downstream of this transfer switch?

 

[DownRiverGUy]

1. That should be "Emergency Load" not "Life Safety" you are correct.

This building will not be treating anyone so this does not fall under 517.
The Emeregency Load is only egress lighting.

2. The nature of the legally required loads are 5 20HP smoke exhaust fans and a 75HP Elevator motor. The building requires that at least one elevator be on legally required for a "area of refuge"

There is a A1 and B1 feed coming into the building (campus utility). The entire campus utility is backed up by the campus generator.

Refer to my ASCII one-line to see what i'm thinking:

Emergency Panel---ATS----DP-GEN ----------------SUBSTATION--Utility
| |
Generator |
Legally Required Stand-By Panel

Now if my logic is correct...

Because the campus uses a generator... and that generator kicks out power within 60sec. and the generator is sized to accomidate the given load... we can directly connect the Legally required stand-by without having to feed it to an ADDITIONAL ATS/Generator.

Does that make sense?

 

[Mike01]

inverter??

inverter??

If you are just powering egress lighting you probally doe not have a verry large load why not use a UL924 rated inverter backed up by the campus generator? By placing the lighting on an inverter you no longer have to supply it from a dedicate transfer switch either as long as the inverter is rated for 90min.

 

[charlie b]

Refer to my ASCII one-line to see what i'm thinking:

Regretably, the forum software does not accomodate that type of drawing.

I think that 701.6(1) has the answer to your question. Your backup source has capacity to handle the entire campus. Therefore, there is no need to provide a separate source, just for the LRSB loads. Also, you can supply the LRSB loads and all other non-emergency loads from the same panels and without separating the wiring systems.

 

[DownRiverGUy]

I agree 100% with your thoughts Charlie. The only reason we showed it as a seperate panel was for ease of maintience. Better to have them all in the one spot rather than around the building.

Thanks for your input

Any other thoughts on this?

 

[Mike01]

Nfpa

Nfpa

is the building required to comply with nfpa99 if so it requires emergency lighting to be restored with "a delay of not more than 10 seconds shall be permitted". although the NEC may not require it different parts of NFPA mignt.

 

[charlie b]

That is why they have a separate small generator for the egress lights. See post #3.

 

[skeshesh]

is the building required to comply with nfpa99 if so it requires emergency lighting to be restored with "a delay of not more than 10 seconds shall be permitted". although the NEC may not require it different parts of NFPA mignt.

Why? the OP already clarified that it's not a medical facility. I don't think there's a reason NFPA99 should apply.

 

[DownRiverGUy]

We are providing a small natural gas generator on the roof for the emergency loads. This is about 40kW worth of egress lighting.

The legally required loads were the big probelm because those are over 200kW.

 

[Pierre C Belarge]

Is the Emergency power generator (10 second, smaller generator) downstream of the larger (supplies all the campus) generator?

If so, does that not defeat the purpose of the 10 sec startup?