On my quest to examine everything about my system,  (GeoMax 2, 2x 300' boreholes with 2 loops in each hole, 4 ton, SE Pennsylvania, 2000 sq ft house), I was looking at the Geo-Flo circulation pumps and researching them on the net.

Now, when I look at the performance curve of the pumps, it lists gpm on the bottom, and "head"/feet on the side axis.  What exactly does that mean for a ground loop?  I know for an outdoor fountain or sump pump, it means how much water can be pumped up to that height and at what pressure/rate it will be.  IE 2 feet - 4 gpm, 3 feet - 3 gpm, etc.

Does it mean the same thing for depth because the water has to go down and come up again?

How does this work with Geothermal loops?

There is no net change in height for fluid flowing through a closed loop.

Head in this case, sometimes referred to as 'head loss' refers to the friction encountered by the fluid as it moves through all the lines, fittings, valves, heat exchangers, etc. It varies with flow - doubling a given flow quadruples the head loss

A responsible designer selects a pump that will overcome the expected head loss in the entire system while supplying the required GPM.

We also use head loss to measure flow through a geo unit heat exchanger. With system running measure the inlet and outlet pressures at the heat exchanger, subtract and compare to the table supplied by the manufacturer.

Hope this helps

You can convert all the head/feet figures to psi (multiply by .43) - which is more intuitive.

I meant to include a conversion factor in my previous post. As Jonr notes it is .43 psi per foot or 2.31 feet per psi.

Thanks, everyone! I love this board for the info and the help. 'preciate it!