2T WSHP...loop HX size required

Discussion in 'General Discussions' started by weedy64, Mar 8, 2016.

  1. weedy64

    weedy64 New Member

    New member.

    Since 2003 I have owned a 5T w2w 5000' ground loop system that heated 3000sq house and pool (as reqd) for years, no issues.

    I moved.

    I am installing a 2T/3T horizontal unit or a pair of 3/4T horizontals in a 3 bay 24' x 44 workshop to heat and cool 1100 sq. ft. Well insulated, 10.5' ceilings. 1 bay with a 15' ceiling. I will run an internal brine loop with a flat plate hx to isolate the water from a 20 ft well next to shop (no longer used for domestic). I plan to pump and dump thru the hx to control loop temp. A second hx may also be installed in the brine loop to re-capture heat from a hydraulic power unit that runs a fair bit. 2 questions:

    Do I seek one 2T/3T or a pair of smaller units and run a 2 stage thermostat?

    Ignoring the hydraulic heat source, how big a hx do I need to isolate the well from the brine?
    - trying for 1-2 close approach. Area of hx flat plate?

  2. geoxne

    geoxne Active Member Forum Leader

    You can't ignore the source. Its temperature and available flow are integral to calculating HX.
    1-2F close approach would be considered unreasonable, requiring huge source flow rates and a huge HX. Most flat plate calculators do not allow approach closer than 4-5F.

    So lets say your open source EWT is 47F. You will take a 5F hit at the HX and another 5F drop at the HP. Now you have HP LWT of 37F. In my opinion, that is to close to freezing for comfort (you can't antifreeze an open source). Compare the cost to closed loop source before you commit to open/HX/closed HP source.
  3. weedy64

    weedy64 New Member

    Agreed 37F is too cold for me too.

    A closed loop is not in the cards, it is not my property, I have a long term lease but I can't dig up the surrounding area. There is a 20ft well 5 ft from building so that is what I have to work with.

    I said to ignore the hydraulic heat source as it is just too intermittent, unknown in quantity and perhaps better cooled separately...chances are it will be running more in the summer when I want to cool the building not in the winter when I want to heat it. Probably a simple radiator inside the building would be best or likely the HPU will have a small shell HX and aquastat on it.

    Back to the ground source issue.

    "requiring huge source flow rates and a huge HX" - I would think that would be relative to the BTU load, which I will put out there at 18000btu.

    I could can run raw water via a strainer straight thru the HP(s) amd avoid a secondary HX altogether but thought that an isolating HX was a good idea as I cant guarantee what material the HP hx will be. I have a couple spare 4.5x20.5" (6 sq ft. area ea.) SS plate exchangers to use for well water isolation and to throttle the brine loop to 60F (McQuays suggestion) during cooling season. Its actually the heating season I'm concerned about, is 12 sq ft enough area to avoid the 5F HX penalty you speak of. These flat plates have 1" ports vs the 1/2" ports of the HP(s) so water flow on the source side can easily exceed the brine side but I dont have the real heat exchanger coefficients for the plates (old Sentry - NOS) to do any meaningful calculations (Im working on Sentry customer service for info). But how different would they be from any other 4.5x20 plate exchanger?

    I haven't actually bought a HP yet but the ceiling mounted horizontal models come up now and again for 3-600 $ so I didn't think Id be out too much on this experiment. It is after all a shop not a custom home and I wear coveralls usually so an even 70F at all times is not a must. And the Northwest is usually just rainy and wet not super cold.

    Thanks for your review.
  4. geoxne

    geoxne Active Member Forum Leader

    My calculator is coming up with 12.5 sqft HX SA with 8 gpm flow both sides to get HP LWT up to 39F. with entering open source at 47F.

    That's a lot of pumping to make it happen on the open source side. You will need to verify the well can do it. While you are at it get the water tested if it is good quality you could go open loop at about 4gpm.
  5. geoxne

    geoxne Active Member Forum Leader

    I am glad you mentioned the usage of the shop and must warn you at reduced indoor temperatures with cold starts and deep set backs the HP extracts more heat than at typical published performance at 70F indoor temp. I calculated your HE load on the HX at 20,000 btu/hr. A higher HE just might push you over the edge.
  6. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    I would always use one larger HP versus a smaller one.

    You must make the heat exchanger larger rather than smaller, your delta T should be as small as possible, 5F if the goal here. If you get hit be a 5 degree loss at the heat exchanger, the second loop between HP and heat exchanger would be a close system, and can get a bit of antifreeze, just enough to make you comfortable with 37F LWT.
  7. weedy64

    weedy64 New Member

    I was just stating that I will be happy at 64-65 to work in, I have no plans to run setbacks maybe 60 but I want it dry inside since I don't want my machine tools to rust or change dimensions so consistent heat is the order of the day. Cooling will be a luxury for me, in the past if it was too hot....go MC riding.

    The HX's I quoted are what I already own....if I read correctly it looks like combined they are close, or I "may" need to add a little more.

    If water is good and plentiful then sure I would run it raw. I think the dairy farmer that I rent the building from may have a relatively current H2O test but I will have to do a pump down test and verify water flow and temp. The pump control and pressure tank are in my shop and not currently powered up. I am about 400 yards from a major river so I think a lot of the groundwater recharge comes from there, it looks like the farm complex is on a gravel bed. I would use a Gr. 26-99 for raw water supply, not the submersible. But the sub. will certainly make priming easy.

    "I would always use one larger HP versus a smaller one" It will depend on what I can find reasonably. My ? was: 1 larger HP unit or 2 smaller ones in a staged set up? Not sure how to interpret your answer.

  8. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    What do you think the ft/hd of a 26-99 will be when used as a well pump? At the gpm you need. My point was that you have to bold in 1 HP versus 2 HP, and the price of a 2 ton is not much more than a 1 ton, so I'd go with a single HP instead of 2 of them. On the other side you seem to looking for the cheapest version.

    You also seem to add much complexity and cost due to your system design in your mind, and you don't even own the place. Not sure if geo will serve you well.
  9. weedy64

    weedy64 New Member

    I think 12-16gpm according to the pump curve I read but I will do a live test first. The well water just isn't very far down.

    "You also seem to add much complexity and cost due to your system design in your mind, and you don't even own the place. "
    - I agree, but family owns it.

    I am in Canada so the cost of a new, ideal unit is too much to bear for a "rental"

    That being said, I am looking for a second hand unit/ slight case damage or whatever to make it affordable. Most of the avail. units are WSHPs standard range, not Geo. so some complexity was dealing with that. The extra costs in my mind generally involve parts I already own: spare HX's and extra pipe, circ. pumps, motorized 3 ways etc. I will have to buy the odd fitting I'm sure, but I will get the benefit of the heating/cooling for at least 10yrs and if I move elsewhere and build a garage I would likely move the equipment if appropriate. Moving this system would be small potatoes compared to the other equip/machinery I would need to move. If I expire before that happens then my family member (owner) gets the benefit, and I wont care.

    I plan to buy a local/ebay HP(s) R410a type and so far 2 smaller ones seem to be a fair bit much cheaper than a single larger one. If I had to buy all new stuff, pumps etc and a new HP then what you say is likely correct. But this is how I see it from my chair at this time.

    Other than Electric, propane or oil there is little else avail. I may end up getting a mini-split installed, that could certainly be moved later.

    I do concede that the plan in my head and what skills, parts, resources I possess have not necessarily been well explained in my posts.
    Sorry, I am trying.
    Last edited: Mar 10, 2016
  10. weedy64

    weedy64 New Member

    After a good nights sleep.... you're likely right. Ouch. I will concentrate on getting an appropriate Geo unit of the right size and not try and over engineer the install to accommodate a wrong fit unit(s). Ill save the money by getting a less desirable 460V 3ph unit and adapt my power situation to that.

  11. Take a look at your powerlines outside, if there is 3 you can only get 2phase if four (3 on top and 1 lower ground) then you can get 480 3ph. You probably will have better luck with finding scrach and dent. Look local ish shipping is killer.

    I like the idea of 2 smaller units, with some problem solving you can set them up like a varable speed system. For example, with a 1 ton and a 2 ton you can run the 1 ton for small loads and the two ton for med loads, and both for peak loads.

    You may also try and build your own unit, you cirtantly have some know how. Find some junk yard units and some copper tubing. For the heat exchanger look at the moonshine liebig cooler pritty much the same thing.

    Its a shop setup as well it dose not have to be perminate if you ever decide to move you can take the pumps with you. I dont regret buying mine :) now i just got to find another one or a bigger one. If you find a hp under 600 in the 240-270v range go for it :).
    Last edited: Aug 5, 2016
  12. weedy64

    weedy64 New Member

    Much has changed with my shop plan. For the good.

    My shop is a long term lease and it is supplied with 240v single phase. I have built a 20hp well balanced phase convertor to run my machine tools and auto hoist, all 230v but with a xfmer I could get 460 if i need it as well.

    Heatpumps: Initially I was looking at a local single phase 3T unit, but the CL flake never returned my calls etc. I then looked at what was available and considered a 3ph unit but didnt really want to run the phase convertor 24/7. Then a deal came along and my friend and I bought some HPs 1 thru 2T 2011/12 vintage. So I have a selection to play with in case my sizing estimates arent accurate.

    I installed a 1T in my home double garage with a direct pressure regulated water feed.

    I am starting by installing a 1T and a 1.5T in the shop. I can upsize if necessary. Im supplying water (pump n dump) directly (no heat exchangers) with a 26-96 bronze pump suspended (in a diving bell (upside down pail)) above the high water line in a 20ft dug well outside the shop, it easily supplys 10gpm for the HPs. The water runs clean but i have not had it analyzed. As you suggest I plan to run the smallest HP for best economy and stage the other as a higher load dictates.
  13. geoxne

    geoxne Active Member Forum Leader

    FYI, if it matters 3-phase equipment is not Energy Star eligible and would disqualify available US Fed Tax Residential Credit.
    Eligibility Scope 2)B -

    B. Excluded Products: Geothermal heat pumps intended for commercial use (i.e., 3-phase units) are not eligible for ENERGY STAR.

    https://www.energystar.gov/sites/de...rmal_Heat_Pumps_Program_Requirements v3.1.pdf
    David Knowlton likes this.
  14. weedy64

    weedy64 New Member

    As a Canadian location and non-residence and used equip, im pretty sure its a non-starter.
  15. Very good point though! I'm sure several readers over the years will read that and save a lot of head ake. Thanks geone :)

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