Minnesota 17yo FHP review and new MHP

Discussion in 'Geothermal Heat Pump Testimonials' started by inwo, Jan 14, 2020.

  1. inwo

    inwo New Member

    Put a FHP 6 ton Geothermal using slinky loops in my new 5900 sq ft house in late 2002. I quickly found that I was using aux resistance heating more than expected. -20F in SE Mn.
    The next year I put a water to water heat exchanger on my loop and added heat from dumping 5gpm of watter from a shallow well. It runs my well when loop drops to 40F. This has allowed me to use zero resistance heating year round.
    Two issues the first month:
    1. A grundfos pump went bad. One of two loop pumps.
    2. A factory defect, stuffing the wires in the compressor junction box, caused a lead to burn off destroying the motor starting device. I was able to solder a lead on the stub that was left on the compressor.

    Worked fine until I replaced it last year. 17 years. I did not want it to fail mid-winter.

    Replacement is a 6 ton MHP, one of the companies that sells direct. The wholesalers 60% markup again kept me from buying local.

    I am having an issue with HP tripping on low pressure. I may post later looking for help. I monitor most of the parameters such as loop flow. Flow is below specs but has always worked fine on original and new HP.
    6.5 lb drop through internal exchanger. Factory specs 8lb, but I never let my loop get below 38F .
    Static pressure is unchanged at <.2 iwc.
    To be continued.
    Pleased to be a member of forum.
    Last edited: Jan 14, 2020
  2. inwo

    inwo New Member

    Oops, found the edit button. :)
    Now to look for delete.
  3. rbento

    rbento New Member

    Dave, I am also a new member.
    I also have a 6 T MHP and have had the same pressure problem. All I did, that I know of, was to reset the main power breaker. This happened maybe two or three times and has not happened again for the past 2-3 months. Since then everything is working great. I like the MHP, very simple. Actually I have 2 units. I also use a 3.5T as the AUX stage three. Same problem the first time I fired the 3.5T up, Had to reset but since all is great.
    Early on I was confused about the thermostat wiring. Could have been the white wire O/B I realized I had to set the thermostat to "O" on cool for the reversing valve..
    Also I found the guy at MHP to be very helpful
    Good Luck
  4. inwo

    inwo New Member

    I got a prompt response to my question from mhp
    Do you know what your flow rate is.
    Power cycling resets, but I had the fault repeating. Mhp tells me that it's most likely a flow problem. Or low refrigerant.

    I don't know if working the desuperheater hard adds to the issue, so I have it turned off for now.
  5. rbento

    rbento New Member

    I don't know exactly what the flow rate is... I have a gauge that reads the entry water on the unit and it says 7.5 PSI. I have had it all the way up to 15 psi by adjusting my flow center pumps and no difference the operation of the unit except that my leaving water temp goes down with the lower pump pressure, and so does my power consumption.... I also have a desuperheater but it is not hooked up yet.
    Since the units come preloaded with refrigerant, and it runs ok now, I ruled that out as the problem...
  6. rbento

    rbento New Member

    Thinking about the flow rate issue, . Perhaps you are getting air in your system related to the addition of the shallow well ? My flow center is one of those non-pressurized types that burps the air out. My 3.5T only had the problem the first time I started it, perfect ever since. Anyway just guessing at this point, trying to help.. good luck

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