Minnesota GeoCool Unit Terrible Performance - Help!

Discussion in 'Maintenance and Troubleshooting' started by Matt Griffith, Feb 14, 2017.

  1. Matt Griffith

    Matt Griffith New Member

    Hi All,

    This is a great forum. I'm a long time reader, first time poster. Hoping someone can help either confirm my thinking or point me in a better direction. Also hoping this gives someone a real perspective on GeoCool units, their warranty, and their distributor's service quality.

    The Loop: Self installed, 3600 ft of tubing buried ~8 ft below a marsh. The loop field is saturated with water and tall grass growing over it.

    The Heat Pump: GeoCool 4 ton, 2 stage. Vertical forced air. One of the first 2 stage units they made.

    The House: 3400 sq ft 2 story with full basement. R21 walls and R50 ceilings.

    Location: Central Minnesota

    The Problem: COP is down to .93, air delta T is low, compressor discharge temp is low,

    System installed ~1 year ago. Performance seemed on the low side initially, based on air discharge temps. Had the compressor stall late last fall, was going to replace it but it started back up again and was drawing normal amps without any new noises. Decided not to replace the compressor due to parts-only warranty (got an estimate of $1000 labor & refrig. only).

    Took some data afterwards and discharge temps were about what they were before.

    Fast forward to late December: Discharge air temps are down to 80-83 degrees, loop temperature is only down ~3 degrees vs before, but fluctuates according to snow melt (warm days actually lower my loop temps due to snow melt).

    I get on the phone with the distributor/sales house and they say take full data. I agree, as I'm a mechanical engineer with full access to data loggers and all the good stuff. I take data and find that my COP is terrible in heating mode and the unit now has 0PSI suction pressure in cooling mode. I also get a suspicious temperature drop across my evaporator, which looks a lot like a restriction.

    Entering Air Temp: 68F
    Leaving Air Temp: 80F
    Air Delta T: 12F
    Entering Water/Antifreeze Temp: 39
    Leaving Water / Antifreeze Temp: 37
    Water Flow: 12-15 GPM (based on delta P across unit)
    Compressor Suction Pressure: 105 PSI
    Compressor Suction Temp: 27F
    Compressor Discharge Pressure: 275 PSI
    Compressor Discharge Temp: 91F
    Compressor Suction Superheat: -6.7F
    Entering TXV Temp: 75F
    Entering TXV Subcool: 15F
    Leaving TXV Temp: 46F
    TXV surges audibly and varies suction pressure by 10 psi
    Compressor Volts: 241
    Compressor Amps: 11.83 (within spec)

    I'm getting terrible service support. GeoCool and the distributor say it's a bad compressor. I'm trying to tell them there's more going on, and asking them to justify the compressor only so I don't drop $1K and not fix the problem. They refuse to do so. It's been a 3 week back & forth battle, with every time promise being broken.

    Any thoughts from others on this? Looking forward to your help so I can either get this solved or educate others who may be looking to go with a GeoCool unit so they know what they're in for...

    Thanks in advance!
  2. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    The system is extracting only about 12k Btuh while using at least 3000 Watts. That's a raw deal.
    TXV is hunting.
    Where is compressor discharge temperature measured? 91*F seems very low
    Waterside DT too low
    Airside DT too low
    I wonder if there are non-condensibles in the system.
    I'm skeptical compressor is to blame.
  3. navyman

    navyman New Member

    Was hoping to get some insight on this problem of his. Did he figure it out?

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