Florida FHP heat pump, clogged heat exchanger?

Discussion in 'Maintenance and Troubleshooting' started by Michaeldinpc, Jun 20, 2015.

  1. Michaeldinpc

    Michaeldinpc New Member

    First of all I'd like to thank all those who have posted here so far. I've spent countless hours browsing reading everything that looked like it might relate to my situation and I think its helped me narrow down my problem. I'm ready to build a flush cart to try and clean out the loop / heat exchanger but figured I'd post my findings here and ask for some advice before I spend the cash on a $1000 tool I might use once a year.

    Long story short I have a closed loop system (no clue on the type or details of the loop) with a Florida Heat Pump GT018-1HZC in my rental. I'm not sure how long it hasn't been cooling efficiently but we've had 80-90 degree days pretty regularly lately and the system has been running non stop to keep the home in the high 70's

    I went out yesterday about 6pm and took a look. the info below is what I found.

    Air temp-
    entering the return is 80.4
    Exiting the supply is 69.1.
    Wet bulb at return is 77.6

    87.8 and 68.3 degrees on the suction
    224 psi and 154.9 degrees on the liquid.

    Water in Loop
    9 psi and 94.8 degree's going into the heat pump
    1 psi and 98.8 degree's coming out of heat pump

    It has a TXV, FHP/ Bosch Tech support is telling me the Target Superheat is 6-12 but cant offer any incite on the loop, said they don't have flow charts either...? I reclaimed and weighed in fresh r22 before taking the pressures and temps posted above, evap looks spotless, Caps and amp draws are all spot on.

    All I have for the unit is the installation and maintenance manual. It does not have a flow chart inside but these numbers seem horrible based on what I've read here.

    By the way I've been in the HVAC field for 20 years, 8 of which where only weekends and summer breaks as a kid working with the family's HVAC business in Norther Indiana, the rest has been here in Florida. I have helped with the rough-in of a hand full of pond loop Geo units, and repaired a few older geo units, but I know little more than what I've read here about diagnosing / servicing of closed loops.

  2. Michaeldinpc

    Michaeldinpc New Member

    BTW There is a "operating temperatures & pressures chart" in the manual mentioned above. I guess I could consider this as the target GPM for the unit?
    When I first bought my PT gauges I threw them on this unit out of curiosity and calculated a much higher GPM, 9 gpm if I remember correctly. I cant find my notes or remember where I found the info to calculate that flow rate based on the PSI going in and coming out.

    Attached Files:

  3. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    I do not like the low water pressure. It will allow entrapped air to form bubbles and block flow.

    Pump it up and test again.

  4. Michaeldinpc

    Michaeldinpc New Member

    Bumped up the pressure to 29 going in 24 coming out (roughly 4.5 gpm) got on my belly / back and found the ball valves buried 35 ft past the crawlspace access and burped it for good measure.
  5. Michaeldinpc

    Michaeldinpc New Member

    Thanks for the reply*
  6. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    What changed? Anything?
  7. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Check the heat rejection to know if your refrigerant circuit works. So far you have conflicting numbers, delta P was 8 psi when your loop pressure was low, after you bumped it up it was 5 psi. If indeed you have only 4.5 gpm flow, and only a 4F delta T, your heat rejection is about 9000 BTUs/h, which is about 40% OF WHAT IT SHOULD BE. Target GPM should be 4.5 gpm, but your delta T should be much higher, 8-10 degrees at least, more like 12F. Please check your delta T again and post back.
  8. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    Please do as Doc suggests

    Airside delta T and long run times suggest something is way off, unless airflow is too high (very rare)

    Low side refrigerant values seem a bit high, but not according to FHP per the linked PDF although superheat itself looks OK, maybe a tad high (~16)

    I wonder if you have measured high side refrigerant temp at correct location...224 PSIG corresponds to a Tsat of about 109*F, so with a bit of subcooling I'd look for a liquid line temp of ~100-105*F. Perhaps you measured temp where hot gas enters the loop heat exchanger? R22 won't exist as a liquid at 224 PSIG / 155*F.

    If you are in fact condensing R22 at or near 224 PSIG with loop water in the upper 90s, that is reasonable high side performance.
    Palace GeoThermal likes this.
  9. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    Hey Curt, good to hear from you

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