Service Sizing for Golf Course Pump Station

[PluggedIn66]

Hello everyone, long time reader and first time poster here.

We are working on an upcoming project, where golf course is upgrading pump station for course irrigation. The pump station is prefabricated and UL listed with 405FLA stamped on nameplate). Pump station is 3PH 480V. The prefabbed station has a 600A fusible main disco built-in (with 600A dual element, RK5 fuses) , and we will also be installing a service entrance rated 600A fusible disco/manual transfer switch ahead of the pump station.. There is an existing 3PH 480V 400A service, fed with parallel 4/0 AWG THWN-2 Cu feeders in (1) 3" PVC conduit feeding previous pump station. Existing self contained meter can is 400/320A rated.

QUESTION: Can I replace the 400/320A meter can with a 600/480A can, and RE-USE the existing feeders? According to my calcs (and using the 90*C column for derating purposes), these parallel feeders are rated for a max of 416A (260A+260A*0.8), which is above the 405A FLA.

The prefabbed equipment with 600A disconnect is making me question whether we need to provide a true 600A to equipment. Other issues throwing me off (which may be a moot point due to UL listing of equipment?)...The pump station contains (4) 75HP motors, (1) 30HP motor, and (1) 5HP motor, all at 480V. My FLA calcs are higher than what is listed (96Ax4 + 40A + 7.6A), or 431.6A. At this point, the existing service feeders would not be adequate.

These pump stations are state of the art for the market, and contain VFD's for all motors...so maybe that is where they are able to decrease the FLA calcs...not sure on this one, or that it even matters.

Anyhow, I appreciate everyone/anyone's time and help on this one!

 

[d0nut]

Does the pump station also have MCA and MOCP on the nameplate?

 

[don_resqcapt19]

...

The prefabbed equipment with 600A disconnect is making me question whether we need to provide a true 600A to equipment. Other issues throwing me off (which may be a moot point due to UL listing of equipment?)...The pump station contains (4) 75HP motors, (1) 30HP motor, and (1) 5HP motor, all at 480V. My FLA calcs are higher than what is listed (96Ax4 + 40A + 7.6A), or 431.6A. At this point, the existing service feeders would not be adequate.

....

Your load calculation is short by 24 amps. Feeders for multiple motors need to have the sum of all of the full load currents plus 25% of the largest full load current.
Not sure how they come up with a nameplate full load current of 405 amps.

 

[Dennis Alwon]

There is feeder size as well as a minimum breaker sized for the loads, I believe

 

[retirede]

Your load calculation is short by 24 amps. Feeders for multiple motors need to have the sum of all of the full load currents plus 25% of the largest full load current.
Not sure how they come up with a nameplate full load current of 405 amps.

Does the multiple motor calculation come in to play even if all motors are integral to a single piece of listed equipment? It could be designed that all motors can’t possibly run at the same time.

 

[don_resqcapt19]

Does the multiple motor calculation come in to play even if all motors are integral to a single piece of listed equipment? It could be designed that all motors can’t possibly run at the same time.

The manufacturer can do anything the listing standard permits.

There is just no combination of those motors that would result in a full load current of 405 amp using the rules found in the NEC.

Most of the listing standard rules as far as total load match up with the rules in the NEC. Would have to know what product standard the equipment was listed to, and then read though the standard to see if the 405 amps is correct.

 

[qcroanoke]

If that is a poco supplied service they would probably tell you the 4/0 is fine. I'd certainly ask.
If not ask the mfgr. Or the engineer if you can swap the fuses to 400. Jmo

 

[Jraef]

Typically in these pre-packaged golf course pump systems, the larger pumps are the only things that will run at the same time. The smaller ones are typically a filter backwash (probably the 5HP in this case) and a lower volume pump for drip irrigation on peripheral landscaping off of the course itself, in this case likely the 30HP, which would not be run at the same time. So my guess is that the max operating load is just the 4 X 75HP main pumps and station power, hence the 405A FLA label.