pressure in return well (for heat pump)

[mbartosik]

I'm still trying to optimize the pumping for my ground source heat pump.

I'm wondering if I would likely have some pressure in the return well which would cause the pump to work harder. The return well pipe goes down to the water level, and the return well head is sealed.

I'm wondering if as water is pumped into the return well pressure will build up in the return well?

I would expect that depends on the ground properties at the water level (it is sandy). If pressure does build up then that could be useful to force the water back into the ground rather than filling the well up (the opposite to draw down), however, since there is little draw down in the source well I would expect that there would not need to be much pressure in the return well to force the water back into the ground.

If there is pressure in the return well and I was to equalize it with the atomsphere then I would expect to need less pressure to achieve the same flow, and thus I could drop the pressure and the motor could do less work.

What do the experts think and advise?

 

[Gary Slusser]

You're right. If the well cap is sealed air can't get out as water wants to displace it and pressure would build up. Plus, there is the weight of the water in the well above the pump's outlet so the pump has to overcome both and.. with the well sealed, air can't get in as the water drains out of the well.

 

[Sponsor]

 

[mbartosik]

Thanks Gary,
I'll have a word with the well driller, and if he does not have a strong reason for not doing so, then I'll fit a small vent hole in the top of the return well, and see if I can drop the pressure further.

I'll post my results here.
So far I've saved about 800W of pumping power, maybe I can save another 150W by fitting a return well vent.