electric supply to fire water pump 11

[jacphi]

i have a controlgear rated for 1200A,480v. one of the feeder is a fire water pump.having a FLA of 240A(locked rotor current 1500A Approx. i am extracting the local std requirement for fire pump unit package.
"QUOTE"
The protection schemes for Fire Pump Unit (FPU) packages shall comply with NFPA 20 and NFPA 70. In general, these standards require that the motor be allowed to operate under locked rotor condition continuously and is only automatically disconnected under short-circuit conditions.
Exception :
The exception to these requirements is that where a FPU package is fed from a bus that has ground overcurrent protection on the incomers or supply transformers, the feeder to the FPU package shall have ground overcurrent protection, and all other feeders connected to the same buses or transformers shall have ground overcurrent protection.
"UNQUOTE"

my question is will this controlgear be sufficient to supply the locked rotor condition mentioned? does the exception above mean that by providing groung fault protection i do not have to comply with require that the motor be allowed to operate under locked rotor condition continuously. please comment.

 

[jraef]

Having previously been in the fire pump controller business I can address some of these issues.

1) LOOK CLOSELY AT THE FIRST SENTENCE OF THE QUOTE. There is no intention for the equipment to actually PROVIDE locked rotor current continuously, because as others have pointed out the motor will melt down anyway. The references in this section are for the PROTECTIVE device (or lack there of). The intent here is to have the system be void of any running over current protection, i.e. long-time thermal trip elements. Since the code must cover the possibility of fuses or circuit breakers they are covering the worst case scenario, fuses. You may not size the FUSES for any less than Locked Rotor Curent so that they dont blow unless you have a destructive short circuit situation. Circuit breakers with magnetic-only trip elements are typically sized at 1100 - 1300% of FLA anyway.

2) Without knowing all of the other loads connected to the 1200A switchgear there is no way of determining if it is adequate or not. Hire a professional. If you do it wrong and have a fire, the insurance adjuster will be looking for this flaw in your thinking as a way to get out of paying!

3) The exception has to do with using a GF trip device on the entire system. If you use it on one part of the system, you must use it on the FPU as well. This is assuming that a coordinated system where GF protection was put in the incommer or transformer will be relying on that GF protection and not necessarily an instantaneous short circuit device. So to maintain the integrety of that system coordination you cannot have one major component, i.e. the FPU, running without GF because other protective devices may not pick up a short circuit in it. In other words, just because it is a Fire Pump doesn't mean you can get away with not using a GF protective device if your system was designed to have one.

4) For those who don't know, a Fire Pump Controller is SUPPOSED to allow the motor to "run-to-destruction". Remember, it will only come on when there is ALREADY a fire and so creating another one in the motor is the least of your problems. Hence the elimination of thermal protective devices. Fire Pump Starters must even contain a method of manually forcing the controller closed even if the coil fails, i.e. a mechanical lever! They are very specialized controllers and must be UL / FM listed (in the US) under a completely different set of standards than regular motor controllers. In most jurisdictions you CANNOT use a standard MCC for a fire pump.

It also needs to be in a red box!



Quando Omni Flunkus Moritati

 

[kfussell]

1. I assume that this is the fire water pump and not a jockey pump.

2. I assume that you are use the MCC to provide a feeder to a UL listed fire pump controller. If not and your are planning to use a starter in the MCC, that is a code violateion.

3. The power to the Fire pump controller should normally be tapped ahead of the service entrance. The feeder becomes in essence another service entrance. This feeder is generally sized at approximately the locked rotor current of the fire pump motor and, if protect4ed, is protected with short circut protection only.

If the rules for service entrance are followed, primary protection is not required on the feeder and it may be run directly to the fire pump controller.

You should not be feeding the fire pump controller from a MCC unit downstream of the service unless you have a reliable redundant source(s) of power to assure service continuity.

 

[jbartos]

Suggestion: In many local Authorities Having Jurisdiction, the fire pump control is reviewed before it is submitted for construction. However, it is a good idea to have it designed flawlessly.

 

[jraef]

LOL! ..."designed flawlessly"?

Only an engineer could believe in such a fairy tale!

No disrespect intended JB, just a humorous observation of your assertion that such a thing as a flawless design might be achievable without divine intervention.


Quando Omni Flunkus Moritati

 

[jbartos]

Suggestion: Visit

http://www.vi.wheeling.il.us/Services/Fire/SprinklerSystemInstallReq.htm

for:
Village of Wheeling Plumbing fire protection requirements
and for:
Fire Pump Requirements
When sprinkler requirements dictate the need for a fire pump, the installation must comply with the following standard:

NFPA #20: "Installation of Stationary Fire Pumps"

 

[mvcjr]

Kudos to jraef for a very informative reply!

Trivia question:
When you say water hose it is water that comes out of the nozzle. How about a fire hose?

God bless!

 

[MerleH]

As has been pointed out, the 1200A MCC is not adequate for a 1500A locked rotor current on a fire pump. Also, if the MCC is downstream of the service, you will need a second source of power. You might want to consider a diesel driven fire pump as an alternate. This would eliminate all of the problems of supplying this power through your plant electrical system.

 

[jbartos]

Suggestion: The Diesel Driven Fire Pump is more or less a fire truck. This is much too much a mechanical engineering item.