Fire Pump Conductor Sizing

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Al Pike

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Honesdale, Pa
I have a 150 HP Fire Pump that's 70 ft from a 3000A service. The Engineer has me installing (4)sets of (3)500mcm and a 3/0gnd in 4in RGS from the FPCP ATS to the service and (1) set of 3-600mcm and a 1/0gnd to the Generator ATS's splice for the Fire Pump feeders. The conductors to the service will be tap'd off of the bus and the generator is tap'd after the 1200A OCPD in a splice box inside the building onto (2) set's of 600mcm w/1/0 gnd that feeds 2 ATS's. The Jockey Pump will be tap'd the same way.

695.6(B)
150hp (430.250)=180A
180A*1.25= 225A

Other than associated loads calculated in why would I have to run anything bigger than 4/0? VD ok but will have to calculate generator after final location.

When I questioned the math I made it worse and was told that I have to size the wires to the generator to the OCPD of 1200A since the breaker size changed. That means they now want (3) sets of 600mcm to the splice.(I'm not sure the splice meets 700.10(B) either.
This is alot of copper to feed a 225A pump.

Thanks for the help
 
Al Pike said:
I have a 150 HP Fire Pump that's 70 ft from a 3000A service. The Engineer has me installing (4)sets of (3)500mcm and a 3/0gnd in 4in RGS from the FPCP ATS to the service and (1) set of 3-600mcm and a 1/0gnd to the Generator ATS's splice for the Fire Pump feeders. The conductors to the service will be tap'd off of the bus and the generator is tap'd after the 1200A OCPD in a splice box inside the building onto (2) set's of 600mcm w/1/0 gnd that feeds 2 ATS's. The Jockey Pump will be tap'd the same way.

695.6(B)
150hp (430.250)=180A
180A*1.25= 225A

Other than associated loads calculated in why would I have to run anything bigger than 4/0? VD ok but will have to calculate generator after final location.

When I questioned the math I made it worse and was told that I have to size the wires to the generator to the OCPD of 1200A since the breaker size changed. That means they now want (3) sets of 600mcm to the splice.(I'm not sure the splice meets 700.10(B) either.
This is alot of copper to feed a 225A pump.

Thanks for the help
Click to expand...

The engineer thinks you have to size the conductors for the locked rotor current. He is wrong. Point him to article 695 and tell him to do his homework.
 
gadfly56 said:
The engineer thinks you have to size the conductors for the locked rotor current. He is wrong. Point him to article 695 and tell him to do his homework.
Click to expand...

Yes I am trying to do that. I've done all the math with VD to controller's and the pump and don't know where I'm gonna land these wires. I hope I dont have to run 4 sets of 500 to the pump.
 
I want to piggy back on to this.
They way I read it the service conductors for the fire pump should be rated for 125% of the pump FLA.
The only modifications would be for voltage drop.
Right?

Fire pump controllers do not even have sufficient lugs for wires sized for the locked rotor current.
 
olc said:
I want to piggy back on to this.
They way I read it the service conductors for the fire pump should be rated for 125% of the pump FLA.
The only modifications would be for voltage drop.
Right?

Fire pump controllers do not even have sufficient lugs for wires sized for the locked rotor current.
Click to expand...

You are correct. However, it would be the FLC (Full-Load Current) versus the FLA.
 
MasterTheNEC said:
You are correct. However, it would be the FLC (Full-Load Current) versus the FLA.
Click to expand...

Very well, you get the Captain Quibble Querulous Correction Cup for this year.;) However, the next time I see a fire pump motor stamped "FLC" instead of "FLA" will be the first time.
 
gadfly56 said:
Very well, you get the Captain Quibble Querulous Correction Cup for this year.;) However, the next time I see a fire pump motor stamped "FLC" instead of "FLA" will be the first time.
Click to expand...

I doubt you ever will see it stamped FLC. The reason someone has pointed this difference out is because FLC has to come from the tables 430. 430.247,48,49,50, and 51. This FLC is very different from the FLA, so your calculation and wire sizing will be very different.
 
While I see people saying that there is a difference between FLA and FLC, there is nothing in the NEC to support that idea. Yes you have to size the conductors per the values found in the tables at the end of Article 430 and yes you have to size the overloads based on the nameplate current.
Per 430.7(A)(2) the marking on the motor nameplate is full load current. Per the heading of the tables the value in the tables is also full load current.
 
don_resqcapt19 said:
While I see people saying that there is a difference between FLA and FLC, there is nothing in the NEC to support that idea. Yes you have to size the conductors per the values found in the tables at the end of Article 430 and yes you have to size the overloads based on the nameplate current.
Per 430.7(A)(2) the marking on the motor nameplate is full load current. Per the heading of the tables the value in the tables is also full load current.
Click to expand...
Hello Don,

This issue is the value they give you to do the calculation, that's what the difference is and that's what the NEC implies. Almost all the time, if not the all the time the nameplate amps aka FLA is less than the FLC from the table. This is major difference in sizing overloads or the conductors.
 
electricg said:
Hello Don,

This issue is the value they give you to do the calculation, that's what the difference is and that's what the NEC implies. Almost all the time, if not the all the time the nameplate amps aka FLA is less than the FLC from the table. This is major difference in sizing overloads or the conductors.
Click to expand...
I understand the two values, but there is just not anything in the NEC that even implies those two terms. The term "full load amps" does not appear anywhere in the code. The term used in the code for both conductor sizing and overload sizing is "full load current".
When I teach that part of the code I use the terms "code current" (or "table current") and "nameplate current".
 
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