DW pressure drops while Geo pumping

Discussion in 'General Discussions' started by clockwalk, Nov 30, 2010.

  1. clockwalk

    clockwalk New Member

    My 4 ton water to air Geosystem is open loop using water from my well. The well was dug 240 feet deeper for the Geo system. At first the 3/4 horse pump was pumping water through the heat pump at 16 gal per minute but the water pressure in the house dropped to 7 pounds. My installer changed the pump to a 1 horse pump but the DW pressure only increased to 22 pounds. He adjusted the ball valves so now the heat pump is receiving water at 4 GPM and we have 70 pounds pressure for house hold use but the water in the heat pump is noisy. Sounds like water running in the house like when you hear someone turn on the shower though nothing is running except the heat pump. If I can put up with the noise am I likely using too much electricity for the 1 horse pump? What would be the best remedy for me so the system is running at the highest efficiency?
     
  2. Bergy

    Bergy Member Industry Professional Forum Leader

    16 GPM is twice the recommended flow rate for a four ton Geo. 4 GPM is HALF the recommended flow. Depending on the incoming water temperature, 1.5~2 GPM/ton is the recommended flow rate.

    There should be a 10 GPM flow restrictor on the system,they are noisy so a ball valve downstream of the restrictor is closed a little,putting back pressure on the water flow, lowering the GPM's and making the restrictor quieter. A pressure reducing valve can be placed upstream of the Geo. Lower pressure equals less noise. Gpm is the only thing that matters, not PSI.

    Bergy
     
  3. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    Run the geo at 1.5 GPM / ton if well water is >50*F. Reduce house water pressure to as low as you can stand. Running a 1 hp pump continually while geo is running eats up most of the geo savings over other heating systems.
     
  4. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    While it is commonly done..... Talking about pumps capacity using the horsepower of the motor is a no know, especially in deep wells with unknown pumping levels. Once you move beyond the "box stock" models it is a slippery slope. A more economical pump motor can be installed with more data to work with. That being said, a flow restrictor plus a ball valve is a "belts and susspender" aproach. One or the other is fine. We have had trouble with flow restrictors being noisy and fouling and only use ball valves at this point.
    Eric
     
  5. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    I admit my remarks were a bit informal - I was thinking of the typical box-stock 1 HP pump drawing 1+ KW. With the flow pinched down to 4 GPM and house pressure at 70, a stock pump may be at a particularly inefficient point on its curve.

    More data is certainly needed - my main thrust was to point out that neglecting pump power is ill-advised, and the steps taken so far seem wanting, judging solely from the OP's description.
     
  6. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    Or worse yet you increase the motor size to address the pressure issue and the gallons needed in the house are still left wanting. Pressure and flow, the two most misunderstood concepts that are closely related to each other but could ot be farther apart.
    I recently installed a 1hp 7 gallon a minute pump in a deep well with a low yield where the standing water table was 25 feet and the anticipated pumping level at 10 gpm was going to be around 165. It is all about the curve.
    Eric

    Curt,
    Have you any thing to report in regard to your deep well reinjection project?
     
  7. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    It is all about the curve.

    As to my project, the wells are in, so the path forward is fixed. I'm told that the static waer level is about 10' below grade except when the local paper co that withdraws 14 MMGD goes into shutdown, during which time wells all over the island start free-flowing.

    I'll be hunting a low pressure moderate flow supply pump for 4-5 tons of HVAC ideally able to coexist with a shallow well irrigation pump situated on the reinjection well.

    Its going to be a learning experience, but it'll work, one way or the other.
     
  8. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    If the wells are in, your fate is cast. It will work, and do not take no for an answer.
    Eric
     

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