Washington Hp Home DIY Geothermal

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

  1. Hp Home

    Hp Home Member

    First post here so I will start with my intro-

    I have 20 years experience as a home builder and I am also very mechanically inclined. I am also a die hard do-it-yourselfer. Currently I am building a new home that our family of 4 will live in for the next 20 or 30 years and I am doing damn near everything myself. I enjoy it and take a lot of pride in my work.

    I have been absorbing information about geothermal for a couple years now. Much of it from this forum, a couple other sites, manufacturers literature, and Caleffi Idronics which I refer back to regularly.

    I also read Manual J and Manual D and put some effort into a good load calculation. Then I used Climatemasters GeoDesigner software to design the ground loops and get an idea of how the system would perform. It was nice to be able to adjust variables and see how it would affect system performance.

    The design the computer program generated for me is a horizontal closed loop, 'six-pipe' design, 300' long trench six feet deep, returning at four feet deep. I ended up modifying this slightly doing what I would call an 'eight-pipe'. Four loops instead of three. The trench is 280' long, 6' minimum depth and 4' minimum width. The pipe is 3/4" SDR11, all 600' long. They run out at 6' deep, then I backfilled 2' and the pipes return at 4' deep.

    Here is a few pics of the ground loop install. I can drive an excavator all day but my good buddy has amazing skills at pulling levers and moving dirt so he drove and I wrestled pipe. I used notched 2x4's to keep the pipes spaced evenly the I removed them as we backfilled. And yes I know working in a trench is dangerous and I should have been wearing my hard hat.



  2. heatoldhome

    heatoldhome Geo Student Forum Leader

    Looks nice to me!

    I am also a DIY guy. Not a expert.

    Wondering if your in a extrem climate (cold winters) like myself will the pipes being so shallow as they enter the house cause problems? The top few feet of ground can get very cold, depending on how much antifreeze you use in the loop will it possibly freeze right in that area?

    Hope a expert will chime in and give there advise.

    Love seeing new projects! Keep up the good work.
  3. Hp Home

    Hp Home Member

    During the planning stages I talked with several different experts including local installers, manufacturers reps and a couple engineers.

    At least two different experts put the idea in my head that a water to water two tank system (hot and cold) would be super awesome.

    Also super complicated but I liked the idea so I ran with it. We live in a heating dominant climate with a/c typically considered an unnecessary luxury. But I start getting uncomfortable when its over 65* outside and my wife is always cold. I could imagine April-June and September-November possibly using both heat and a/c.

    Here is an example of the type of system I am planning. Just delete two of the heat pumps and one of the fan coils, and make it a non-pressurized flow center for the ground loops.

    Geo system.jpg
  4. Hp Home

    Hp Home Member


    I have read your thread it has been inspirational to see a successful DIY install.

    We rarely get hard freezes in the ground here, water lines can be 18" with no problem.

    The pipes there might be pushing like 12" but its also right next to the house and drops off quick.

    Planning to run antifreeze and when flowing the fluid will only be in that spot for a few seconds on its 600' journey.

    Basically that was as low as I could get it without tunneling under the footing.
  5. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    looks good, I assume you are trying to support a 4 ton water-water heatpump with your loop field?
    How do you plan to make your hot water? I would also bypass the buffer tanks and send the chilled and cooled water directly to the zone.

    Tell us more about your radiant system? Top of the floor with heat transfer plates?
  6. Hp Home

    Hp Home Member

    After the ground loops were done I moved on to the radiant slab portion.

    I have only done a couple heated slabs but if I ever do it again I want to do a couple things different.

    Mainly I don't like the uninsulated footing areas. Next time I want to find an engineer who is on board with continuous insulation. Code will not allow it without an engineers blessing.

    Thing is after talking with concrete experts I decided to go 5" thick instead of 4". The footings need to be 8".

    But what if the slab was 6" thick with an upgraded rebar schedule in the load bearing areas? The insulation has plenty of compression strength and a slab is stronger with a uniform base and thickness.

    Anyways here is a picture of what I have, it's permanent now whether I like it or not. Tubing is 9" o.c., 6 circuits of 1/2" pex all 300' long. Slab is about 1500 sf.


    Also I will throw in a picture of how I did the slab edge insulation. Seems to be a frequently asked question with radiant slabs.

  7. Hp Home

    Hp Home Member

    The heating load calculated at just over three tons. Then I added R6 rockwool exterior insulation. But the Climatemaster W2W is either a 3 or 5 ton so I went with the new TBW036.

    One question I am still pondering is if I could or should just not use one of the loops?

    The plan for hot water is desuperheater to a 40 gallon buffer tank and a 50 gallon electric finishing tank. There seems to be so much mixed feedback on the desuperheaters so I am curious to see what my experience will be.

    I was thinking with the cooling I need a buffer because my load is not necessarily exactly matched to the heat pumps output? (2) 50 gallon Caleffi Termo con tanks are on a truck somewhere on their way here as I type this. Part of the reason I went with those tanks though is their versatility- in case I end up configuring things differently, add a solar setup, etc.

    Radiant slab main floor will act as one big zone (open floor plan). Upstairs is three bedrooms with thick carpet and 2 bathrooms. So I am planning for radiant walls upstairs. This will be a new experience for me. More on that in a month or so.
    Last edited: Dec 31, 2015
  8. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    Hi and welcome.

    I like your work. I like 9" oc. I like 2 tanks. Water to water is my favorite way to move heat.

    I am working with a fellow in Southwestern, Ohio. It is two tank water to water. As I sift through a new to me control system I will keep you posted or at least point you in their direction.

    Why non-pressurized?

  9. Hp Home

    Hp Home Member

    Thank you!

    I went non-pressurized mainly because it seemed more user-friendly to a do-it-yourselfer, so that I could purge the loops without a purge cart.

    I seem to recall reading (probably on here?) debates about the pros and cons of pressurized vs non-pressurized.

    I went ahead and pulled the trigger on the non-pressurized and then realized they must make a huge profit selling those units, a circulator and an expansion tank would have been a lot cheaper!

    The control system and some of the piping details are two areas I will likely need some guidance. I have done the research and have my head wrapped around the theory but implementing it all in the real world can be a different story.

    I have the HBX Controls Eco-550. The plan is to run the main floor slab and hot buffer tank with an outdoor reset. Upstairs the radiant walls will get a Tstat in each room with actuators on the manifold valves. I just need to get enough tubing in those walls to match or beat the temp requirement of the slab.
  10. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    You are welcome.

    I get why some folks would use a flow center, I know how to size pumps so I skip the rest of the plastic and add an air eliminator. I do this on both sides of the W2W. Both ideas work, but since I know how to build a formula then add the numbers. I prefer to buy just enough pump. I also know about differential by-pass valves and delta P & T ECM drive pumps and how to design for their use.

    I know and use Tekmar and the HBX is my next wire to rely study. Perhaps we can learn together. Piping depends on what the control system thinks and what it will do. I would have you look at the HBX 1000 series.

    I would zone your radiant up and down and then sub-divide the upstairs by room using actuators. (Now go look up differential pressure valves). We can regulate the heat out put of the wall panels with the length of the heat emitter times BTUH/ square foot. The folks at Caleffi have an Idronics issue, dedicated to wall panels. Start there and I will feed you more if needed.

    I hope someone shared the magic for using 1/2" pex is keep the loops under 300' EACH.

  11. heatoldhome

    heatoldhome Geo Student Forum Leader

    I have the Hbx-1000 I'm sure the 550 is simular. If I can help let me know.
  12. Hp Home

    Hp Home Member

    I did learn about the 300' limit for 1/2" pex before I did the slab so I bought all my pex in 300' rolls.

    I feel there is a lot for me to learn on the control side of things. But I am a little better with electrical than I am with plumbing so I should be able to figure it out in time.

    I was thinking the HBX 550 was a good match for my system and the HBX 1000 adds more features and expansion capabilities than I need? I could be missing something...

    I have 3 radiant manifolds, a 6 circuit for the slab and (2) 3 circuit upstairs. My plan was to use a Wilo variable speed pump to supply these, so no differential pressure valve required? The slab would always circulate with outdoor reset adjusting the water temp accordingly and upstairs would circulate when a tstat/actuator calls for heat.

    I cannot find an Idronics issue about radiant walls but I did read the Manual of Modern Hydronics which has a chapter on it. I would love to absorb more information about this, there is not a lot out there and it is not (in my experience) a very common method. In fact outside of the internet no other contractors I know have even heard of it, the response is usually "why not just do heated floors?" If I answer "carpet" I get blank stares. If I answer something like "water temperature" or "heat pump efficiency" I get some real funny looks like I'm certfiably insane.
  13. frankz

    frankz New Member

    Nice system, but I wonder, what is the rationale for a cold water tank? I can see you might want a hot water buffer for all those slab zones, but since there is only one fan-coil, seems there would only be a need for a buffer tank if the heat pump and fan coil were significantly mismatched, and why would they be?
  14. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    The cool tank is for air conditioning in the shoulder seasons. Cooling the air without cooling the floors.

  15. Hp Home

    Hp Home Member

    I could be wrong but my reasoning was that we are in a heating dominant climate, so the heat pump and fan coil could be matched to each other but would be oversized for cooling the building.

    It seems to me like it would short cycle the heat pump in cooling mode without the buffer tank.

    Also I am planning to use the fan coil for dehumidifying and I am not entirely sure how that fits the sizing equation either.

    I think it would be a lot of intermittent, low or part load use and I could set the buffer tank to a delta T that would give the heat pump appropriate run times.

    But I am a DIY with very little experience in this field, I should probably be putting a question mark at the end of every sentence I type. Learning and figuring all this out is why I am here.
  16. heatoldhome

    heatoldhome Geo Student Forum Leader

    Keep in mind the 3 ton w2w will be more like 2-2.5 ton in cooling mode depending on water Temps on both sides.

    I'm going to switch my setup over before next summer to have it setup like a hot and separate cold tank but my cold tank will be the air handler coil. With seeing it run for a short time at the end of the last summer I'm very confident it will work flawless.


    Being it sounds like you already bought the cold tank you might as well install it.
    I highly recommend the buffer tank tee setups on both tanks.

    You could also plumb it with some valves and tees so you can easily try it with or without the cold tank by simply flipping a valve or 2.
  17. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    For the climate around here, there is not much value in a hot and cold tank. We have a few weeks in the shoulder season or either end where we don't need either heating or cooling. And then it is just one for the next few months.

    That being said, we still have two tank systems out there, but I'm not talking clients into them anymore.

    Now if we used high temp w-w units I could see selling it more to get domestic hot water in cooling season.
  18. Hp Home

    Hp Home Member

    I did not consider the volume of the coil. Out of curiosity I might do a little math and see how that would work. But yes the tank is already purchased.

    Someone I know is putting in a system right now and they are doing a single tank setup where the tank will be hot in the winter and cold in the summer.

    I didn't do that on mine because in the shoulder seasons I would want the slab to stay warm for the cold evenings & mornings but have a/c available to cool the upstairs in the afternoon.

    The guys that put this idea in my head do mainly large commercial buildings.

    If it was for someone else I would not do this either, unnecessarily complex for a typical residential homeowner.

    But I'm a tinkerer and I will probably be tinkering with this system for years to come.
  19. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Your radiant looks good.

    How much did the heating load calculate? Keep in mind that the w-w capacity is not 12,000 BTUs/ton, more like 9,600/ton, less with antifreeze. Might want to get the 5 ton, specifically when you will ask the HP to to many things.

    Anyway, what I refer to as buffer tank bypass, Andy (HeatOldHome) calls Buffer Tank Tees, and Waterfurnace now calls "Load Direct". It is a new way of ensuring that the hottest (or coldest) water is sent directly to the zones, and does not get mixed down by the return water in the buffer tank. It significantly increases the efficiency since you can decrease the leaving load temperature. It is different than the diagram you have posted here. It requires a variable speed circulation pump for the zones, which you are getting.See conceptual diagram attached.

    And yes, I would make my hot water fully with the geo system, and skip the desuperheater installation.

    Attached Files:

  20. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    >>>>watches the heat move.

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