Washington Hp Home DIY Geothermal

Discussion in 'Geothermal Heat Pump Testimonials' started by Hp Home, Dec 30, 2015.

  1. Hp Home

    Hp Home Member

    Heating load calculated at 36,950 BTUH. Temperature bin analysis report shows the heat pump running 100% on a design day or colder, about 100 hours a year.

    But that was with R21 walls and R38 roof. I now have R36 walls and R60 roof. I also already have the 3 ton unit with the desuperheater option.

    I am interested in the buffer tank tee method, where can I learn more about this? I am about to dive into Idronics 17...
  2. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Buffer tank Tee explained by John Manning. Let me know if you need so detailed diagrams.

    The 3 ton W-W has a heat capacity of around 27,000 BTUs /hour, minus what the desuperheater steals, I'll keep my fingers crossed that you have enough capacity. The bin report by the software can be a bit misleading.
  3. heatoldhome

    heatoldhome Geo Student Forum Leader

    Thanks for posting this Doc. It's something the contractor I worked with advised against, but I'm happy I piped it both ways to see the results for my self. After playing with it for a little while it was obvious the bypass (tee) worked much better.

    I will try any change my vocabulary to call it the buffer tank bypass. :)
  4. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Your contractor might not seek to advance and do better and evolve in the interest of his customers, and in the interest of himself. Even Waterfurnace scoffs about it, calling it "load direct" and rolling their eyes. I guess it was not invented in their house. They are good in building heat pumps, but they must understand that it is up to the designer/installer if that very same heat pump runs at a COP of 4 or a COP of 2.
    It all comes down to the monitoring, where you can actually measure the difference.
  5. Hp Home

    Hp Home Member

    Thanks for the video, that was interesting. Good point he made about flow rates being to high to allow stratification to happen in the tank.

    One question I have is does this change the heat pump run times?

    I had been using an equation to calculate how long the heat pump would run to raise 50 gallons of water by ten degrees.

    With a portion of the hot water now going direct to the load does it take longer to satisfy the aquastat in the tank?
  6. heatoldhome

    heatoldhome Geo Student Forum Leader

    Typically most controls systems only allow the buffer tank to be heated when at least one zone is calling for heat. So your sending btus to the zone and the buffer tank.

    Your calculations of x amount of time to heat 50 gallons 10 degrees would only be true if all the btus went to the buffer tank.

    So in short yes, no matter how you pipe it if one or more zones are on it will take longer to raise the buffer tank temperature to the desired temp.
  7. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    There are two options here. Sending the load water (partially) directly to the zones sends hotter water to the zones, and will satisfy the zones quicker, resulting in lesser run time, thus increased efficiency. Alternative you can lower your load temperatures and serve the zones with the same water temperature, since the water does not get mixed down anymore in the buffer tank, which results in the same runtime, just much more efficient due to lower load temperatures.
  8. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    One needs to think of the tank as a giant hydronic separator. Piped as such, one does not need the "magic T".

  9. heatoldhome

    heatoldhome Geo Student Forum Leader

  10. Hp Home

    Hp Home Member

    Currently I am working on electrical rough in.

    On a new construction install would you ask the electricians for anything in particular?

    Right now I have 6 circuits planned-

    Heat pump- 40A (TBW036)
    Air handler- 30A (240v)
    Water heater- 30A (50 gallon electric)
    Circulators- 20A (5 or 6 115v pumps)
    Vent fans- 20A (HRV & bath exhaust)
    Backup heat- 30A (not used, future)

    I was thinking of mabey a switch for each circulator?

    Is there any reason to have more than one circuit for the circulators?
  11. heatoldhome

    heatoldhome Geo Student Forum Leader

    Look at the max breaker size for your gshp listed on the nameplate. My 3 ton w2w says 30 amps max. Yours may be different but probably not.

    Why so many circulators?

    Only reason for having more then one breaker for circulators would be if the combined total wattage was to high for one circuit. Or if your worried about the possibility that one pump could fail and trip the breaker turning off all your pumps.

    You might want to pick a location for your controls and have a outlet or 2 at that location.

    If you want to add logging like a wel data logger you will want ethernet at that location also.
  12. Hp Home

    Hp Home Member

    Thanks that is really helpful advice on the controls and data wiring.

    I thought the 40A seemed like an odd size but that is what is in the IOM. Mabey I will unpack the heat pump and double check the real thing.

    For the circulators I was planning one from heat pump to hot tank, one from heat pump to cold tank, one from hot tank to radiant zones, one from cold tank to fan coil, and one for the ground loops. Possible sixth pump to pipe hot water to the fan coil but I'm not sure if its worth it or necessary or even a good idea.

    Wattage wise I think a 20A circuit could handle about 30 or 40 of these little circulators but pumps and motors often times have restrictive code requirements.

    The point you make about one failure on a pump interrupting everything has me thinking about doing more than one circuit.
  13. heatoldhome

    heatoldhome Geo Student Forum Leader

    It's possible your gshp shows a higher amperage max breaker because it's designed to power the loop pump and or load to buffer tank pump. Mine is not.

    You can use a single circulator to pump to both the hot and cold buffer tanks.
    Keep the circulator on the gshp side of the valves that switch from hot tank to cold tank and it will do both.

    Think about using just one delta p pump on each buffer tank to feed the load. This is just a suggestion you can do it both ways.
    Last edited: Jan 9, 2016
  14. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    You will be wasting electricity by running the circulator you do not need. Keep in mind, they will be running a lot. We now only put 2 on the load side and 1 on the source side.
    One of them has to be a variable speed, due to the changing flow requirements of the zones. Zones are opened by motorized zone valves.
  15. Hp Home

    Hp Home Member

    Thank you yes this makes more sense I thought it seemed like a lot of circulators. I'm glad I can reduce that.
  16. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Let us know if you need help with the setup or design.
  17. Hp Home

    Hp Home Member

    Thank you I'm sure I will have many questions along the way. The next part of the heating system to go in will be the radiant wall panels and some ductwork but I am still at least a month away from starting that.
  18. Hp Home

    Hp Home Member

    I am back on the geo project after many months of working on other things.

    I roughed in the electrical and built a custom steel and wood staircase then finally got into the radiant walls.

    Radiant walls is something I had never done or even seen done before so I was figuring it out as I went.

    I ran it all in between the studs so as not to mess with door jamb widths, electrical box depth, etc.

    This was labor intensive to cobble all the blocking and foam board into the stud bays but the material cost was not too bad.

    The aluminum heat transfer plates was the most expensive part.

    IMG_1983.JPG IMG_1982.JPG IMG_1981.JPG IMG_1979.JPG

    This is all on the second floor of the house which is lofted, these rooms have pretty small heating loads.

    Each room is its own zone and has its own tstat which control actuator valves on the second floor manifolds.

    My plan is for outdoor reset to set water temp based on the main floor slab and hopefully the same temperature water will be adequate for the radiant walls.
  19. Hp Home

    Hp Home Member

    Next step was to drywall and paint the mechanical room.

    Now the fun begins.

    A couple pics of what I am working with-

    IMG_2087.JPG IMG_2088.JPG IMG_2089.JPG

    Trying to find the best arrangement for everything is like playing tetris. Also trying to look into the future and think about access for servicing.

    50 gallon water heater, 40 gallon desuperheater buffer tank and air handler I squeezed real tightly into the corner to leave as much room as possible for the heat pump.

    Climatemaster says 3 feet clear space on the front and one side is minimum, 3 feet on front and both sides is preferable for servicing.

    The ground loops come up through the floor behind the two ThermoCon tanks and there is a non pressurized flow center hiding back there as well.

    Somehow I need to get the flow center positioned in a way I can fill the reservoir or I might just end up getting a big funnel.

    The PVC sticking up behind the Thermo Con tanks is a temporary cap for the ground loops. I know to not use PVC, I am making copper manifolds.
  20. ChrisJ

    ChrisJ Active Member Forum Leader

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