Generator and Fire Pump

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charlie b

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Diesel generator is located in one room within a building, adjacent to main electrical room. Generator serves a switchboard in a separate, smaller room that is within the main electrical room, but separated from it by a fire rated wall. The generator switchboard has a main breaker.
1. Do I need a generator breaker at the generator itself, or is the main breaker in the switchboard in the room next door sufficient?
2. Can I use a generator breaker at the generator itself, and leave out the main breaker in the switchboard, if that works out better for selective coordination purposes?
3. If I wish to power a fire pump from this generator (and not also from the utility ?normal? source), can I connect it to the switchboard, or must I tap the generator feeder upstream of the switchboard, or does that depend on my choices from questions 1 and 2?

(Note: I am heading out to a project site shortly, and will not be able to read comments or reply until late this afternoon.)
 

RB1

Senior Member
If the generator is inherently protected, conductors sized in accordance with 445.13 are considered protected and no circuit breaker is required at the generator. However, a means of disconnect, or some other approved method of shutting the prime mover down must be provided within sight of the generator.

The circuit breaker at the generator alone is acceptable if located within the same building.

I think the fire pump requires a separate breaker at the generator per 695.4(B).
 

charlie b

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I will have to look at the code book on Monday (I don't keep one at home, for a reason ;)). But let me ask what you mean by "inherently protected."
 

yucan2

Senior Member
I don't see how powering a fire pump from the generator only unless the generator has been approved and tested for and runs 24/7, can be done legally. Utility power must be in this loop.

If the generator is running 24/7 is that why you didn't mention a transfer switch? I assume the fire pump controller will have its own internal ATS added to the equation as well.

A fire pump can not be dependent upon a generator only unless it is the sole source of reliable "primary power".

In addition to 445.13, as the generator will be powering a fire pump and locked rotor current must be considered, spend time in 695.3 thru 695.6.

A number of other items also come into play like enclosing conduit in fire rated raceway or keeping the run outside until penetration, etc. etc.

Sounds like this is an add-on to an existing installation? Be diligent.
 
Generator conductors are generally inherently protected by the engine controls; there isn't enough overload capability to damage the feeder.

That said, about 25% of the inspectors seem to require local disconnects. It is especially a problem when you have a parallel plant and a separate room for the paralleling gear.
 

RICK NAPIER

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Location
New Jersey
NFPA 20 covers fire pumps and power for a fire pump needs to comply with 9.2.2. I don't think the situation you describe would conform but you cou possibly use a diesel driven fire pump if power is an issue and that is found in chapter 11 of the same code.
 

charlie b

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I don't see how powering a fire pump from the generator only unless the generator has been approved and tested for and runs 24/7, can be done legally. Utility power must be in this loop.
Can you give me a code citation that backs up this claim? As long as I can get the generator started, whenever the fire pump is needed, why must utility power be part of the equation?


I concede that the design does not look like a good idea, and I am rethinking my options. But I would appreciate knowing whether there is a code-related reason to add another ATS to the package.
Sounds like this is an add-on to an existing installation?
No, this is a new building, and the project is in the middle of the design phase.

 

RB1

Senior Member
Charlie,

Inherent protection can be achieved by collapsing the exitation of the generator on overcurrent. There are other methods available.

If the generator meets the definition of an "on-site power production facility" it can be used as the sole source of power for a fire pump. Otherwise, a utility source is required per 695.3(A)(1).
 

yucan2

Senior Member
Can you give me a code citation that backs up this claim? As long as I can get the generator started, whenever the fire pump is needed, why must utility power be part of the equation?

I concede that the design does not look like a good idea, and I am rethinking my options. But I would appreciate knowing whether there is a code-related reason to add another ATS to the package.
No, this is a new building, and the project is in the middle of the design phase.

Long day for me it was.

Anyway looks like RB1 addressed part of your concern and as for the other an additional ATS has to be incorporated and should undoubtedly be part of the Fire Pump Controller. It will receive a feed from the generator and a feed from a separate and distinct service or disconnect. Distinct actually meaning remote from any other close proximity disconnect(s). 230.72(B)

A separate service is usually the less convoluted solution or a tap ahead of and in a different enclosure (section), than the service disconnect or other disconnects. 695.3 (A)(1).

In summation the need for the additional ATS becomes apparent.
 

charlie b

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So thats how one becomes a senior member? 100 posts! Had I only known :grin:
Oh, that is just a temporary title. You don't get to keep the "senior member" designation until you undergo our "special initiation ceremony." ;)

 

charlie b

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Seattle, WA
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Electrical Engineer
Thanks for the replies. I now understand that two power sources will be needed for my installation, and that the transfer switch will be incorporated into the fire pump controller. My next issue will be to determine, (1) At which points I tap into the normal and backup distribution systems, (2) Whether I need (or whether I can't use) an OCPD somewhere along the tap, and (3) How to size the OCPD.

This project is second on my list for today. When I get back to it, and after I get a chance to look into these questions, I will let you know if I need additional help.
 
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