Fire Pump Feeder Questions

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ed downey

ed downey

Senior Member
Location
Missouri
I have two items regarding Fire Pumps that I would like to bounce off of everyone.

1.) If you have two sources feeding a fire pump (one being the utility and the second being an onsite generator). The Primary source needs to sized at locked rotor current indefinitely {2002 NEC 695.3(A)}. Does the generator feed also need to be sized at locked rotor current or can it be sized at starting current only per 2002 NEC 695.3(B)(2)?
2.) The second item is regarding the feeder protection of the two feeds to the fire pump ATS. Does the feeder from the generator to the fire pump ATS need to be encased in 2? of concrete or any of the other items listed in 695.6(B) or can the exception to 695.6(A) {Exception: Where there are multiple sources of supply with means for automatic connection from one source to the other, the requirement shall only apply to those conductors on the load side of that point of automatic connection between sources.} be used and only the feeders on the secondary side of the Fire Pump ATS Be encased if they are not located within the same room?

Thanks,
Ed
 
Re: Fire Pump Feeder Questions

One of my favorite topics - Fire pumps. We recently completed an installation similar to yours in New Jersey. The AHJ there held that the feeder from the generator to the fire pump ATS had to be routed outside of the building or encased. No exceptions. We argued the exception to 695.6(A), but to no avail. :mad: His argument being that if the power was off and the building was burning, the feeder from the generator was vulnerable. He further held that the generator output breaker had to be sized for locked rotor of the fire pump. We sent a formal request for interpretation to NFPA but did not get an answer in time.

Buy NFPA 20 if you don't already have it. Also, I'm sure you already know, but your transfer switch has to be rated for fire pump use. Huge (emphasis on huge) price difference.

Good luck.
 
Re: Fire Pump Feeder Questions

Brad
Excellent commnets. We took over a fire pump system a few years ago and it was a big expense. I work on instrumentation for a large water system, I prefer gravity storage as gravity is 100% reliable.
 
Re: Fire Pump Feeder Questions

The exception to 695.6(A) is intended to apply to multiple building campus type arrangements.

It is interesting that according to the title of 695.6(a),this rule applies to service conductors, which are absolutely required to be routed outside the building. However, the last sentence of 695.6(a) applies to feeder sources for multibuilding campus type arrangements, hence the reference to 695.3(B)(2). This sentence only applies to the normal source of supply, that when installed in accordance with 695.3(B)(2),is required to be from two or more feeder sources unless the feeders are supplied from separate utility services. In such cases only the conductors common to the multiple normal feeder sources are required to be routed outside the building.

The conductors from the generator are permitted to be installed in accordance with 695.6(b)

[ January 10, 2006, 04:03 PM: Message edited by: rbb ]
 
Re: Fire Pump Feeder Questions

Brad,

Thanks for your comments.

I cannot see how the AHJ can say that the generator breaker needs to be sized for LRA. 695.3(B)(1) specifically indicates that it only be sized for normal starting & running of the motor(s) driving the fire pump. Also 695.4(B) States that Overcurrent protective devices between an onsite standby generator and a fire pump controller shall be selected and sized according to 430.62 to provide short circuit protection only.

I think this answers my first question.

Regarding the second question I don?t think I can use the exception to 695.6(A) because Article 100 defines Service Conductors as the conductors from the service point to the service disconnecting means. Since we first go to a generator distribution panel (which includes the overcurrent protection I talked about above). The conductors from the generator distribution panel to the fire pump would fall under 695.6(B) Circuit Conductors.
:mad: :mad:
 
Re: Fire Pump Feeder Questions

The exception to 695.6(A) is intended to apply to multiple building campus type arrangements.
Click to expand...
695.6(A) doesn't say anything about "multiple building campus type arragnements." I think it is clear if you have a generator and a automatic transfer switch, you don't need to route the conductors outside or encase them in concrete.

Also, I don't think that the title of that section ("Service Conductor") means it only applies to service conductors. The title is telling you that you should install a single feeder to the fire pump as if it were a service conductor.

Steve
 
Re: Fire Pump Feeder Questions

Steve,

No it doesn't say multiple building campus type arrangements. It says 695.3(b)(2), which is feeder sources for multibuilding campus style arrangements. Otherwise 695.6(a) applies to service conductors and 695.6(B) applies to feeder conductors. By definition the conductors between the generator and the fire pump controller are feeder conductors.
 
Re: Fire Pump Feeder Questions

Ed -

I fully agree. NFPA 20-9.6.5 further states that the overcurrent device at the generator must be capable of picking up the full pump room load instantaneously. NOT the LRA.

If our genset had not coincidentally been fitted with an output breaker that happened to meet the LRA, we would have pushed the issue with the AHJ. As it happened, it did, so we didn't.

Take care.
 
Re: Fire Pump Feeder Questions

Thanks for all your responses I think I have a better understanding of the fire pump electrical connection requirements.
;)
-Ed
 
Re: Fire Pump Feeder Questions

rbb:

If I understand you correctly, we disagree on two points.

1) You seem to be saying the exception to 695.6(A) is only an exception to the last sentance of 695.6(A). I think it is an exception to the entire paragraph 695.6(A).

2) You seem to be saying that 695.6(A) only applies to service conductors, and does not apply to a feeder from a generator to an ATS. I think it is saying a feeder from a generator to an ATS should be "installed as a service conductor". In other words, it should be installed outside or protected. But the exception says we don't even have to do that.

So I don't think feeders from a generator to an ATS need any special protection.

Hopefully, someone else will chime in with their opinion.

Steve
 
Re: Fire Pump Feeder Questions

Not my opinion, just a ruling by the AHJ in Cranbury, NJ and upheld by the State of New Jersey Electrical office - the genset feeder to the fire pump ATS needs to be encased or outside the building.

But, that's just one state out of 50. You might get a different opinion in the other 49.

Good luck.
 
Re: Fire Pump Feeder Questions

Steve,

Lets take a closer look at your interpretation of the exception. If I chose to install two services for the fire pump as permitted by 230.2(A)(6), according to your interpretation I could run these conductors through the building without any protection at all. The only protection that would be required is from the load side of the transfer switch to the fire pump controller. This exposes the building to the hazard of unprotected conductors.

I believe the intent of 695.6(a) is to require service conductors to be routed outside the building, it then extends the same requirement to feeder conductors wired under the provisions of 695.3(b). This makes the requirements for feeder conductors wired in accordance with 695.3(B) more restrictive than what is required for other feeder conductors wired in accordance with 695.6(B). The exception to 695.6(A) is intended to relieve this more restrictive requirement where area protection is provided by having two feeders constituting the one normal source as required by 695.3(B).

This is just my interpretation.
 
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