NFA 20 2013

[hhsting]

I have dedicated utility service that feed service rated fire pump controller to fire pump 100 HP, 480V, three phase. I need to know the circuit breaker internal in the fire pump controller trip rating so I can size equipment grounding conductor between the controller and fire pump NEC 2014 section 250.122(A). NFPA 20 2013 section 10.4.3 says that manufacturer have circuit breaker as mentioned with instantaneous trip. However, I am confused their is also NFPA 20 10.4.4 which require locked rotor overcurrent protection as well in addition to breaker internal to fire pump controller.


I exactly don’t understand so manufacturer would have to set 10.4.3 and 10.4.4 as well? My service rated fire pump controller internal has circuit breaker with shunt trip and they say size of breaker is 250A for 100 HP 480V three phase fire pump. Is that not small? I think trip setting could be higher.

 

[cuky2000]

Beware that the Art. 695 of the NEC provides a protection philosophy for a fire pump that is different than other motor loads. The fire pump motor must run, regardless of the risk to destroy the feeder conductors.

The next size standard overcurrent protective device (OCPD) must be selected to carry indefinitely the sum of the locked-rotor current of the fire pump and jockey pumps motor(s), and 100% of the ampere rating of the fire pump’s accessory equipment. it should be noted that when a “listed” fire pump OCPD is used, protection is allowed and specific trip settings are listed per the NEC 695.4(B)(2)(b) and NFPA Std 20:9.2.3.4.1.

Fire pump feeder must also be protected from a building fire as well. It is a common practice to size it for a max drop voltage drop of 15% during motor starting conditions, and secondly 5% at 115% of FLA during running operation.

_{NOTES:
1) Fire pumps electrical design and installation must comply won't only with the NFPA 70: National Electric Code (NEC) Article 695 but also with the are NFPA 20: Standard for the Installation of Stationary Pumps for Fire Protection Chapter 9.
2) For a single utility power source, the NEC requires to confirm that less than a 4-hr shutdown in the previous year.}

 

[hhsting]

@ cuky2000 post is questioning NFPA 20 chapter 10. The breaker post #1 is talking about is inside the listed fire pump controller NOT between utility and fire pump controller. How does NEC 695 come into play?

 

[cuky2000]

Both standards are supplementing each other. Primarily the NFPA 20 covers the fire pump selection, reliability Issued and fire room usually enforced by the local fire marshal. The NEC (NFPA 70) scope specifically cover the requirements for the electric installation of fire pump. Many States adopt the NEC as pert of the local Building Code that made this a enforcement compliance by thE AHJ.

 

[hhsting]

@cuky2000 my understanding is that NFPA 20 chapter 10 covers breaker inside fire pump controller and breakers outside of fire pump controller between utility and fire pump controller are sized per NEC 695 also same information mentioned in NFPA 20 but chapter 9. So my previous question how does NEC 695 come into play with breakers inside fire pump controller?

 

[cuky2000]

Correct, the breaker size, rating, and setting inside the fire pump controller is in the scope of the NFPA 20 and should be permitted by the NFPA 70 assuming the fire pump package is listed. Usually, the AHJ should not object if the nameplate says listed by an acceptable recognized agency such as UL or FM.

The concern regarding the shunt trip setting should be addressed with the controller manufacturer. In many instances, the fire pump controller could use some type of reduced current starting. In any event, both the NFPA 20 & 70 requires that the Circuit breaker tripping mechanism should be set so that it will not operate when the current in the circuit is excessively large.

 

[hhsting]

@cuky2000 how does one size equipment grounding conductor between service rated fire pump controller and fire pump? I thought NEC 2014 section 250.122 says based off of upstream breaker setting. Upstream breaker in this case is in fire pump controller. So one would size the equipment grounding conductor between service rated fire pump controller and fire pump based on breaker tripping inside the fire pump controller? If not then how does one size it?

 

[hhsting]

@ FacEngrPE those are phase conductor sizes. We know how to size phase conductors. It says per phase. Table does Not say equipment grounding conductor sizes

 

[FacEngrPE]

I miss read the wiresize table in the eaton fire pump controller manual. The post as the post does not say anything else so it is deleted.