OVER-SIZED PUMP/UNDER-SIZED WIRE?

[Jazzman]

I was helped on this site sizing pump for low -producing well that is 358’ deep. I ordered 3/4 hp 5 gpm Flowise submersible and #12 gauge wire. However, the supplier substituted a 1 hp 5 gpm pump without telling me. The 1 hp pump is rated maximum for 400’ for #12 wire and I’m at about 420’ from sub-panel. I’m way out in the country ready to install but wondering if I should hold off and get correct pump. Also, I’m pumping into storage tank and I will have only 25 gallons of water above pump in casing. Is this 1 hp pump too big?

Thanks!

 

[Reach4]

740 ft of #12 is even too light for 3/4 HP.

 

[Sponsor]

 

[Jazzman]

740 ft of #12 is even too light for 3/4 HP.

Hi, the distance from sub panel to pump is 420’ not 740’.

 

[Reach4]

Hi, the distance from sub panel to pump is 420’ not 740’.

Ahh... You were including ~ 338 (down to the pump) in your number 420 number. I misinterpreted.

Yes, the AIM manual says #12 is good for 400 ft with 1 HP vs 480 for 3/4 HP. Also, you may need to account for drop to the subpanel. I am not sure. It's close, but the AIM manual numbers would have some margin built in.

A 3-wire pump will draw less power through the breaker during starts and if it has a run capacitor also, it draws a little less power while running. The AIM manual does not seem to get that nuanced in Table 11.

 

[Jazzman]

Thank you so much for the detailed clarification. It is a 3-wire Pump. I also thought that it is important to size pump to well recovery rate and my well recovery is not quite 1 gpm. Bigger isn’t necessarily better from what I’ve read. It am at remote cabin with pump in hand, so I’m tempted to drop it in well...

 

[Valveman]

20' extra will be fine. As long as the total length is 420' then #12 will work, barely.