Need help with my geothermal system

Discussion in 'Open Loop' started by carflipr, Oct 4, 2010.

  1. carflipr

    carflipr New Member

    I purchased a house with an open loop geothermal system already in place. The unit was over 20 years old and the compressor shorted out. I decided to replace the entire system. The new system is the same size as the old system (4 ton) but advertised as much more efficient. It seems to work a lot better than the old one in the summer (cooling) We had a very hot summer and it didn't run very much to keep up. However, the heating capacity seems worse than my old system. I notice that on the spec. sheet for my new unit the entering water temp is 86 for cooling and 66.8 for heating. I'm running my unit on an open loop with a constant water temperature of 55 degrees. Is there an adjustment I need to make for my cooler water temps? I attached a set of gauges and noticed that the output pressure and therefore temperature is pretty low.
    Thanks for any advice,
  2. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader


    what brand heat pump is the new one.

    Most brands work well with water down to 30°. Yours should be happy with 55°
  3. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    Gut instinct

    Is focus on the source side. More efficient means more btu's come from outside the house so you may need to increase flows or such to adjust.
  4. tstolze

    tstolze Member

    Without being sure of your new system, it is possible that it is a 2 stage unit. It is almost certain in these temperatures that it would be running in the 1st stage. This would give you the effect that it has less capacity than your older system that I assume was a single stage system. Two stage units typically run at 66% in the first stage.
  5. carflipr

    carflipr New Member

    Additional info

    The unit is made by Miami Heat Pump (Miami Heat Pump Miami,Florida -Index) Here is a link to their spec. sheet:
    The system is single stage. I'm pretty sure I have enough water. With a gauge connected to the low side pressure I reduced the water flow and could see the pressure drop, then I increased the flow until I had maximum pressure.
    The unit seems to be very efficient in terms of how many BTU's it is putting out versus how much energy it consumes, but is is not using much energy. The compressor is only pulling about 11 amps.
  6. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    Pressure drop

    You need the change in pressure to determine the flow. Units are indifferent to operating pressures.

    Take the readings on either side of the unit and compare to their performance charts. Water temp as well.
  7. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    why do you think that the unit under performing?
  8. pjssailor

    pjssailor New Member


    When was this unit installed? This past summer?
    It seems to me that the Water side is working about right and the temperatures are such that it ought to be putting out lots of heat.. Where are you locatated? The measuring the water side is about like measuring the air comng into and out of the condensor of an air cooled unit. (The hot side in the summer)

    I would try a couple of things. On the first warm day I would switch to cooling and see if it still cools. To do this I would first shut down and let it set for at least 5 minutes. Then switch to cooling and set the thermostat low enough to kick it on. You may have to wait a bit before it turns on but if it turns on and blows lots of cold air, it tells you the refrigerant has probably not leaked out. Or it it has, very little.

    If it does not cool now it probably means one of 2 things. Either the reverseing valves are not working as they should or you have lost some or all of the refrigerant (a leak).

    In either case, it will require someone with more tools and test equipment than I have.

    Have you talked with Miami Heat Pump? Try a call or an email.

    One more thing - is it possible you are in a really cold climate with a light cooling load and a heavier heat load? And is it possible your old unit had an electric heat strip. If your old thermostat was a 2 stage unit you probably had a heat strip. I don't think Miami put heat strips in their regular production.

    I probably would see if I could find a serviceman who would, for an accepable price, hook his pressure guages on the refrigerent side and see what the pressures were on the high and the low sides. If they are low, then I would have him check for a small leak (slow leak?)

    Low heat is no fun most anywhere in the US this time of year. So good luck and keep us posted what you find. PJSSAILOR
  9. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    Gauges should be the last step in the troubleshooting process. First should be GPM, then delta T of entering and leaving air and water. Let's start there.
    Is system reaching set point on the thermostat?

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