GSHP pumping

electricaleng

I have a 70 room hotel, 4 stories, with a gr. source heat pump system in upstate, NY.  It has a single 15 hp pump rated 300 gpm @100' head to circulate through a reverse return piping system within the building, and out to 36 - 400' deep wells under the parking lot.  The wells are manifolded into 6 supplies and returns, each with an unused motorized valve.  in the summer we have about a 14 degree drop across the well system, but in the winter we have a 2 degree drop.  I would like to save some pumping energy by closing off some of the ground wells automatically with motor operated valves, via the EMCS.  How can I estimate how the head loss will change as I close off parallel piping paths in the ground wells?  Also, how can I save electricity by slowing the pump down with the VFD.  By using a pressure sensor?  and should the sensor be at the pump or at the farthest end of the bldg piping?

Mark Eatherton

Why would you want to do that?

GSHPs need as much surface area/heat exchanger as they can get.



If you want to do something that is variable speed, consider using temperature differential to dictate pump speed and flow.



Honeywell makes a nice 0 to 10 VDC controller that can monitor delta T.



I see no operational advantage to closing down well bores tho...



ME10

Tom Blackwell_2

Individual HP units

Options depend on how the individual heat pump units are set up. Does water flow through all heat pumps all the time or only those that are in operation? If each HP has a water control valve, then you could control the pump speed based on differential pressure. If the system is constant flow (all heat pumps flow water all the time), there is not much that ca be done without starving the individual units. I agree with Mark, you need to utilize all the wells at all times-there is nothing to be gained by limiting the amount of ground heat transfer.