Feeders for fire pump

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nickelec

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How would you size the Fedder off a generator for this fire pump?
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125% of FLA (212) is 265A. 2 runs of 2/0 would look correct to me if there are 60° lugs at either end and if you are running THHN CU in concrete encased raceway. If I am missing something please tell me!
 
It's not concrete encased , and again do I size the Fedder for the breaker in the ats or do I size it per the motor

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nickelec said:
It's not concrete encased , and again do I size the Fedder for the breaker in the ats or do I size it per the motor

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Is the ATS part of a combination fire pump controller/ATS?
 
Since there is a significant distance between the generator and the fire pump, you will need to be careful to meet the requirements for starting and running voltage drops
 
Distance aside for now in general would you size the conductors for the ats breaker size or the pump load

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Are you in NYC? The emergency feeder OCPD is sized at between 150% and 300% of the FLC of the fire pump. From the NYC Electrical Code:


695.4(B) Disconnecting Means and Overcurrent Protection.
(2) Generator Supply. When required to be connected to an emergency generator, fire pumps and
limited service fire pumps shall have overcurrent protection selected in accordance with the following,
except where direct connection is made in accordance with 695.4(A)(3) Exception 1:
(1) Fire Pump. Fire pumps shall be protected by an over current device selected at not less than
150 percent and not more than 300 percent of motor full load current.
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I should have noted that what I posted is from the NYC Electrical Code. Sorry about that, I'll make the change.
 
I'm trying to figure out if the exsiting install is compliant I don't do much emergency installs

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Uget an FLC of 211 at 150% i get 316.5 amps next size up is 350 my guess is 400a is a sufficient size OCPD but the conductors I'm having trouble seeing that as compliant 2sets of 2/0 gives me 175 per set for a total of 350 , so do I just down size the breaker or leave it alone

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nickelec said:
Uget an FLC of 211 at 150% i get 316.5 amps next size up is 350 my guess is 400a is a sufficient size OCPD but the conductors I'm having trouble seeing that as compliant 2sets of 2/0 gives me 175 per set for a total of 350 , so do I just down size the breaker or leave it alone

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The conductors and the OCPD do not have to match for a fire pump supply circuit. The OCPD is only providing short circuit and ground fault protection so it can be larger than the conductor size. The conductors are sized at a minimum of 125% of the FLC. (211*125% = 264 amps)

For NYC electrical code your OCPD would need to be between 150% and 300% of the pump FLC on the emergency circuit.
 
nickelec said:
So the two sets of 2/0 are sufficient then

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#2/0 copper is rated 145 A (60 deg), so it's 145 x 2 = 290 A, good if your lines are short.
Your OCPD should only be designed to trip only on short-circuit. Referring to 430.251(A) for locked-rotor amps, a 75 HP motor has a LRA of 1200 A.
 
topgone said:
#2/0 copper is rated 145 A (60 deg), so it's 145 x 2 = 290 A, good if your lines are short.
Your OCPD should only be designed to trip only on short-circuit. Referring to 430.251(A) for locked-rotor amps, a 75 HP motor has a LRA of 1200 A.
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Just curious why you wouldn't use the 75° C ampacity of 175 amps?
 
The only reason I know of is the lugs in the equipment. So long as they are rated 75°C, you can use the 75°C column for sizing. Just be sure voltage drop requirements are met if the runs are long.
 
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