Fire Pump Feeder, Maybe It's Me

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infinity

infinity

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We have a 480, 200 HP fire pump controller fed with a single 3 conductor, #4/0 Vitalink about 300' in length. From T430.250 the motor draws 240 amps so the #4/0 is too small. We're being told that we need to upgrade the feeder to 3-#350 single conductor Vitalink. (I didn't check the calculation factoring in the VD requirement). They want to abandon the existing 3C, #4/0 cable and run three new single #350 kcmil Vitalink cables. I suggested just running a second 3C, #4/0 parallel to the existing but that was met with a luke warm response. Anyone have an opinion on which method is better? Looks like the contractor will be on the hook for the cost so to me the single additional cable is a no brainer.
 
The second 4/0 would be much more cost effective and would reduce the voltage drop even more that the single 350 kcmil, as two 4/0s would be 423.2 kcmil.
The only issue would be making sure you have a physically parallel path for the new cable to meet the requirements for parallel installations.

EDIT: If these are feeder conductors, there might be an issue with the cable EGC size based on 250.122(F).
 
don_resqcapt19 said:
The second 4/0 would be much more cost effective and would reduce the voltage drop even more that the single 350 kcmil, as two 4/0s would be 423.2 kcmil.
The only issue would be making sure you have a physically parallel path for the new cable to meet the requirements for parallel installations.

EDIT: If these are feeder conductors, there might be an issue with the cable EGC size based on 250.122(F).
Click to expand...
IIRC, cables feeding fire pumps are treated as service entrance conductors.
 
don_resqcapt19 said:
EDIT: If these are feeder conductors, there might be an issue with the cable EGC size based on 250.122(F).
Click to expand...
Good point. Yes it's a feeder, there is a service disconnect in the service room before it exits and runs about 300' to the fire pump room. With Vitalink the outer jacket is the EGC so I don't believe that paralleling two sets would have an issue with increasing the EGC size.
 
Can transitions at the terminations be used and the conductor be sized based on the 90 degree ampacity which would make the 4/0 ok, or would the voltage drop be too high?

If not, I like the parallel cable idea, I have run parallel 250-4 MC on several occasions.
 
electrofelon said:
Can transitions at the terminations be used and the conductor be sized based on the 90 degree ampacity which would make the 4/0 ok, or would the voltage drop be too high?

If not, I like the parallel cable idea, I have run parallel 250-4 MC on several occasions.
Click to expand...
Voltage drop for fire pumps is a code rule, not more that 15% below the rated motor voltage at the motor terminals while motor is starting and not more than 5% when the motor is running at 115% of full load current.
Sometimes the utility has to be forced to provide a bigger transformer to meet the start up voltage drop rule.
 
don_resqcapt19 said:
Voltage drop for fire pumps is a code rule, not more that 15% below the rated motor voltage at the motor terminals while motor is starting and not more than 5% when the motor is running at 115% of full load current.
Sometimes the utility has to be forced to provide a bigger transformer to meet the start up voltage drop rule.
Click to expand...
Yes. Presumably the VD was checked before the cable was specd? Then again it was undersized using 75 degrees so who knows what else was missed.🤪
 
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