Low head pump

What's the most efficient pump with the following requirements?

Pumping from a 30" cement cased well--25' total depth
Dynamic level of ~18 ft.
10gpm @ a total of 40' head.
About 40-50% run time.

This is for an existing GSHP system that's currently running off a deep well with a 1.5hp pump.

Any help would be greatly appreciated.

At the most you need 10 GPM and 65' of head. The smallest submersible you can get is a 1/3 HP. A 10S03-6 Grundfos will do 10 GPM from 105' of head. This is a little more than you need but still 5 times smaller and more efficient than the 1.5 HP you have. It is hard to find a 1/3 HP anymore. Let me know if you can't find one.

Thanks for the reply.

The 40' head includes the dynamic pumping level. Here's my calculations on costs with a 50% run time (I think my average actual run time is lower; I haven't been able to get a good estimate.) Please correct any of the wattage values as I'm not positive on these numbers--other than the current pump.

Pump Watts Cost at $0.10/Kwh
Existing 1 1/2hp 2200 $960/yr
1/2 hp @ SF load 960 $420/yr
1/2 hp @ Full Load 670 $294/yr
1/3 hp ? ?

I can't find any info on the 1/3 hp motors/pumps.

Also, is there any way to get a fairly accurate watt usage when you derate(?--not sure of the term) a pump by limiting the gpm pumped? I know you do this fairly regularly with cycle stop valves. Is there any kind of a calculation to determine pumping costs in these situations?

Thanks

tkeoki said:

Also, is there any way to get a fairly accurate watt usage when you derate(?--not sure of the term) a pump by limiting the gpm pumped?
Is there any kind of a calculation to determine pumping costs in these situations?

Click to expand...

HP = GPMxHeaD/(40xEFF)
E.g., 100x120'/[40x50%] = 6.1 hp
and so
EFF = GPMxHD/{HP (40)}
Some pumps give efficiency numbers on the GPM/HD curves.


If 1 1/2hp costs $960/yr
and
1/2 hp costs $294/yr then
1/3 hp should cost approx.
{0.33 x 666} - 39 = ~$180

Or, 1.5/$960 = 0.33/$X
then $X = (0.33) $960/1.5 = ~$210

but the best way is to graph your numbers using Excel and see how the curve looks when you extend to 0.33 hp.