New to Geothermal and need advice

Discussion in 'General Discussions' started by Thoma Mattox, Oct 11, 2017.

  1. Thoma Mattox

    Thoma Mattox New Member

    My wife and I just bought a house that uses GeoThermal... I understand the principals and am excited about the system. The system is a Water Furnace Model P040TL110NADSSA open loop geothermal unit with a dedicated well. The well pump is a 10-gallon per minute and is connected to a pressure tank/pressure switch. Flow through the geothermal is controlled by an Orbit control valve. The previous owner hadn't had maintenance performed in over 2-years so I called the local Water Furnace dealer and scheduled maintenance and asked for a brief overview of things, as a homeowner, I should be doing. I now have a handful of questions...

    1) When the system shuts off, we get a monster water hammer. The service tech indicated a couple thoughts about it. He said that the pressure differential over the coil (23psi in and 14psi out) indicates that the Orbit control valve may be open too far allowing too much water to flow through. He also recommended looking for a "slow closing" valve. Ultimately, he left indicating that the water hammer was no real issue and to not worry about it... Figures 3-days later the PVC pipe ruptured and we had water pouring EVERYWHERE. I can't help but think that this was caused by the water hammering... So, what do I do about the water hammering??? Is there a different control valve I should consider?

    2) Desuperheater. Mine appears to be plumbed weird. All the diagrams I have seen show the inlet water coming in from a cold water source above the water heater and the "heated" water entering through a valve at the bottom. Mine all plumbs through a valve at the bottom (both the cold water AND heated water). Further, anytime the geothermal is operating I can feel HOT water running through both lines (even when no hot water is being used in the house). This seems me.

    3) The above mentioned tech indicated that the desuperheater should NOT be used in the winter. Just wanted to see if this was correct or not.

    Thanks for the help...
  2. geoxne

    geoxne Active Member Forum Leader

    With a 9psi drop you are flowing 11 gpm according to the specification catalog for your unit here-
    5 gpm would be recommended for an open loop system, if your entering water is 50F or above. Anything more is a waste of water and pumping power. appropriate sized fixed flow regulators such as Hays 2305 or Dole GC should be used to ensure proper flow rates.
    Check your pressure tank to make sure the bladder has not blown. Usually the air in the tank is adequate to absorb the shock that causes water hammer. Turn the pressure down in your dedicated system. The HP only needs enough pressure to provide adequate flow, usually 30psi or less. Your Orbit Valve may be over sized. Generally, a good quality, properly sized irrigation valve will close slowly.

    It appears you have a concentric fitting piped at the bottom of you hot water tank. When your HP is running along with the desuperheater pump, the system is trying to heat water in your tank even when you are not using it.

    In heating mode approximately 10% of your HP's capacity is diverted to make hot water. If your unit is not large enough to provide all the heat your house needs, then consider disabling the desuperheater during cold snaps.
  3. Befouself

    Befouself New Member

    Good think what this kind of topik exist on this orum, as i see people get help here ! Good think!
  4. Thoma Mattox

    Thoma Mattox New Member

    Thank you very much. The service company sent a tech out today to replace the valve (they are charging me less than I could get the valve for off of Amazon). The tech indicated that the previous owner had way too much water going through the system (estimated over 11gpm). He also said with that much water running through the system and the rapidly closing Orbit irrigation valve it is no wonder we had a huge water hammer. He replaced it with a TACO valve, throttled the volume of water back, verified the pressure tank was not water logged, and then we inspected the discharge. Apparently, the previous owner just has this system discharge to the surface behind a shed in the backyard. With it pumping 10gpm+, it is no wonder the back yard became a marsh any time we were running the system a lot.

    The tech indicated that we may want to consider discharging the pipe into a 4" drain tile and burying it a few feet below ground. His fear is that this winter we may develop an ice dam or other obstruction to the existing 1" surface discharge waterline. How are normal open loop system water generally managed? I was initially thinking of using the water with a sprinkler to distribute it across the lawn...but, he said the backpressure may not be good for the system.
  5. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    The proper method is to return the water to the groundwater table you pulled it from - a discharge well.

    But you can discharge to a buried cistern or culvert. Something that can handle the very large volumes that you will generate in the middle of winter.

Share This Page