Garn hydronic design

Antman Posted By Antman, Dec 31, 2015 at 7:18 AM

  1. Karl_northwind

    Karl_northwind
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    Feb 13, 2012
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    go to flatplateselect.com GEA makes all sorts of cool sizes, like 5x20 heat exchangers that will give you really close approach temps.

    If you want, PM me with your outputs from flatplateselect.com and I'll look over them for you to make sure things make sense.
     
  2. Karl_northwind

    Karl_northwind
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    Feb 13, 2012
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    go to flatplateselect.com GEA makes all sorts of cool sizes, like 5x20 heat exchangers that will give you really close approach temps.
    if you want, PM me with the outputs from there and I'll look them over to make sure they make sense.
     
  3. Antman

    Antman
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    Sep 27, 2015
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    I did read both of Dan's books and idronics and I have to say that, considering the 23' rise on the highest point of house 1 along with the benefits of a closed and pressurized system, I makes sense to go ahead and pressurize in the Garn Barn.

    On another note, I inquired what size fittings come on the logstor 1.5" dualpex (1.6" ID) and I was told the compression fittings are 1-1/2" MPT. I'll have to call back to clarify that there is no bottleneck because the submittal sheet for uponor's version of 1-1/2" MPT indicates the ID of 1-1/2" WIPEX MPT compression fitting is 1.24" which would create a bottleneck in 4 places, right? One bottleneck at each end of both underground lines. How much this would impact the system's performance?

    Since I'm trying to maximize the system's performance, I'm reconsidering trench and foam. 2" hepex with 2" WIPEX (both ID 1.6") would eliminate the 1.24" bottlenecks. The trench and foam method would take longer but seems that it could be better - more R value, less head loss, and more maneuverable. I'm 99% certain I can make it water-tight. I'll post the bluemax/fiber/XPS demonstration when I get time later today. How much of a difference in performance would I see having the 2" WIPEX over 1-1/2" WIPEX?
     
  4. Antman

    Antman
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    Sep 27, 2015
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    Hope this demonstration transfers OK. Bluemax/fiber/XPS for trench and foam
     
  5. Karl_northwind

    Karl_northwind
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    either will be fine. the ID over the long distance is what's going to kill you. the couple restrictions in the joints won't matter. the 2" hepex and foam will be cheaper by a long shot than the 1.5" logstor. and probably just as good if your ground doesn't move much if at all.

    I don't know what wipex is, but 1.5" ID smooth pipe for 600' at 10 gpm and 30 deg delta T = 150,000 btu and 5.5' head.
    1.25" ID smooth pipe for 600' at 10 GPM and 30 degree delta T= 150,000 btu and 12 feet head.
    1.00 ID smooth pipe for 600' at 10 GPM and 30 degree delta T= 150,000 btu and 31 feet head.

    I'd split the difference and get the 1.25, and use a Taco 0015 on high or viridian VT 2218. for each zone with the check valve between the supply and return tees as above, and a 0015 on low to keep the pipes hot and move water thru the DHW HX. when one or both the Fan coils turn on, it'll add it's head to the slow 0015 primary circulator, but use minimal energy for the 24-7 pump, and not start pumping cold water thru the air coils. it'll have hot ready for you.
     
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  6. Antman

    Antman
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    Sep 27, 2015
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    For my underground lines, I think I'll use 2" Hepex (1.629" ID) for house 1 (500' primary loop) because it really isn't that much more expensive than the 1.5" Hepex (1.244" ID). I already have 1.25" Hepex (1.054" ID) for house 2 (600' primary loop). My plan is to wait until spring or summer to trench and foam both underground runs when the outside conditions are optimal (dry and 85F). In the meantime, can anyone suggest the best way to bring the lines into the attic through a wooden soffit? I am anticipating 2-3' lengthening of the hepex at 180F for each home. I'm curious if this lengthening and expansion of the underground lines disrupts the closed cell polyurethane foam (PUF) in a trench and foam application any more than the pre-insulated products? I plan to do as Tennman suggested with 6mil plastic (1' wide by 2' deep trench, high voltage line in the bottom, backfill, 6mil plastic, 4" PUF, lay down lines, additional 4" PUF, overlap 6mil plastic and waterproof the joints using blumax/fiber, goal is 1' x 1' x 550' = 550 cu ft or 6,600 board feet PUF for both runs combined).
     

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  7. JohnDolz

    JohnDolz
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    Head to San Diego. I can connect you with a ton of folks older than you, all training as if they are heading to the Tour:).
     
  8. Karl_northwind

    Karl_northwind
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    it'll add a little pipe, but make a large wide arc with the piping. the bottom of that run will move quite a bit, and turning that 90 up the wall won't help.
    swing the pipe out from the wall at 90 degrees to the eventual direction, and curve it toward the other end point, and that arc will absorb a lot of that expansion. a piece of drain tile or 2 around it in that are will provide some air space for the pipe to push against rather than just soil. that's just thinking, not something I've ever had to do. I've always had enough curves in the pipe that it could move a little.
    karl
     
  9. Antman

    Antman
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    I have a 500' primary loop which is predominately underground. I think I can use 1-1/2" hepex but I am trying to determine if 2" hepex to minimize head loss in this long loop could possibly be too large? On page 15 of the Garn Design Manual a 2" nominal plastic pipe intersects 0 at what appears to be ~12 GPM and ~1 or 2 FPS. Does this mean I can only operate the primary circ at 12 GPM or higher? What problems would I have with velocities of less than 1 FPS?
     
  10. Karl_northwind

    Karl_northwind
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    bubbles will collect at high spots. There is such a thing as too big a pipe. it may not cause you any problems, depending on lots of things like how your system is piped and where you have air elimination points. or it may.
     
  11. Bob Rohr

    Bob Rohr
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    Once you drop below 2 fps,the water doesn't entrain the air bubbles as well and getting all the small micro-bubbles purged may be a challenge, especially if you have any ups and downs in the piping. If the small bubbles collect and form a large bubble you could get an air lock.
     
  12. Antman

    Antman
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    Sep 27, 2015
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    I appreciate your idea of constantly circulating through two 5x12(20) FPHX with a 0015 on low. Could you look at my redrawing to clarify if this is what you were describing? Also, if I were to go ahead and put the water to water FPHX at the highest point in the system, couldn't I put air vents on both sides of it ( a manual one on the open side and an automatic on the closed side) to take care of any problems with air lock associated with the low velocity on the open side that comes with using 1.6" ID buried pipe?
     

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  13. Karl_northwind

    Karl_northwind
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    if your primary loop is short, I think you'll be fine. the parasitic losses of a long piece of pipe like that will be high.
    really I was thinking that your whole distribution system in the house you wanted to be open. your design as planned would probably work fine (without looking at it too closely) I would move the return sensor on the 0013 VDT closer to the Flat plate hx. it'll respond really slowly as is.
    karl
     
  14. Antman

    Antman
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    Sep 27, 2015
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    Many thanks to the great guidance here. I am firming up my design and looking to trench and foam in 10mil plastic wrapped and sealed with bluemax liquid rubber as soon as the outside temps are ideal (at least 85F). I need to clarify one more thing and is has to do with the supply pump. Is there any reason I can't place it 250' from the Garn hot water supply (HWS) where the pipe comes back out of the ground and into the FPHX? If this is possible, is there a minimum distance a pump can be from the FPHX? I'm assuming not, because I've never come across a minimum distance on a distribution side. Just wanted to get feedback from the experts on this issue or any other concerns with my schematic. Thank You.
     

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  15. leon

    leon
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    Feb 3, 2013
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    Hello Antman,

    Contacting a hydronic circulator specialist at B+G or TACO and go from there as you can very easily
    put your circulator on a reversing timer to push the same water back and forth using a smaller single pipe pex in insulated solid ADS tubing

    Chatting wit B+G or TACO sales representative is going to solve this for you the first time and avoid spending extra money.

    This is the only way your going to solve your current piping issues. I would also upload your
    drawings to www.heatinghelp.com if you are now a member.They are all plumbers
    over there and will help you too.
     
  16. Karl_northwind

    Karl_northwind
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    Feb 13, 2012
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    Generally, you'll want the circulator as close to the GARN as possible. There is math in the Garn design manual for calculating out the NPSH available for your circulator in any location. I would keep the circulator (unless there is some other overpowering reason) as close to the GARN as possible. The GARN in your place is the point of no pressure change, and you want to pump away from that, and as close as possible to it.

    off hand, I'd throw a check valve in the primary loop between the supply piping and the return piping. this will keep the supply piping from pulling backwards thru that connection. and make sure you have flow checks in all the branch circulators.
     
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  17. Antman

    Antman
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    Sep 27, 2015
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    So I have spray foam contractor who is going to help me trench and foam closed-cell PUF next month, but he doesn't want to spray into plastic for some reason and recommends spraying into tyvek house wrap. So rather than fighting with trying to add a layer of plastic around the foam for additional waterproofing, I have decided to spray directly into the ground.

    The frost line here is 1' and the water table is listed at 1', although the 2 houses and the trench are on high ground (10-20' higher the the surround farmland) so I doubt the trench will ever be under water. To make it easy on everyone when it comes time to spray, I plan to suspend two 2" hepex lines at 18-20" deep using stakes on either side of a 1' wide x 2' deep trench. At the very bottom of the trench I'll put a 2" electrical conduit for high voltage and two 1" hepex lines for hot and cold water. Then, spray foam the entire bottom half of the trench which puts all the foam below the frost level and gives me a 1'x1' block of closed-cell PUF below any potential ground heaving which really isn't an issue in our relatively warm climate anyway (i.e. 18 degree F day). After the foam has cured, I will add a 1" irrigation tubing for control wiring before backfilling.

    My question is this... should I add sand in the trench?

    We are near the New Madrid fault line, but otherwise the ground is mostly clay and unlikely to move. I'm just trying to decide if the extra effort of adding sand is worth the risk of attracting water to my PUF block that I'd like to keep dry
     

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  18. Buzz Saw

    Buzz Saw
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    I don't think sand will draw water but rather let water drain away.

    Our pond had a sand vein and would never stay full. Until the day we dug it out and repack the trench with clay. The clay is holding all our water in now. Pond level is up 2' now.

    Sent from my SM-G900V using Tapatalk
     
  19. leon

    leon
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    =====================================================================================================

    The NEC requires electrical conduit above the water lines if my memory is correct, normally its in separate two trenches with high voltage (600Volts +)

    The P waves (pressure waves) from an earthquake will liquify clay soils in a heartbeat, so its a question of what is an acceptable risk fo you with your trench?

    Bedding a utility of any kind on a layer of sand is simple easy insurance.

    The Tyvec is just another layer of insurance for you pipe and conduit run. It would be simple enough to build a box frame on caster wheels to hold it in place as he sprays the foam and move it up as the work progresses.
     
  20. Karl_northwind

    Karl_northwind
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    You'll find probably that any sort of material is better than bare ground. the foam gun will blow around all sort of dirt etc, contaminating the foam. My guy won't spray onto bare ground. tyvek would be OK I guess. He's probably melted regular poly with the curing temperature of the foam.

    I'd do the electrical off to the side, but still at least 18" to the top of conduit, more under a driveway. I always run extra conduits etc.
    sand is OK for drainage, but I'd use pea gravel or 3/4" washed rock if you have it available. but make sure you're not draining it towards your house.

    karl
     
  21. Antman

    Antman
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    Sep 27, 2015
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    It's been a long summer and we installed underground lines and built a chase to get 2" Hepex into the attic. The Hepex was converted to 1-1/2" Hepex once in the attic. We are planning to build the manifold at the highest point in the attic.

    Will the manifold diagrammed here hydraulically separate the primary and secondary?
     

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  22. Karl_northwind

    Karl_northwind
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    yes, but it will not necessarily separate the secondaries from each other. to do that you want to get the manifold flow rate under 2 feet per second flow rate at full flow minus one load.
     
  23. Antman

    Antman
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    Sep 27, 2015
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    At design conditions (100,000 BTUH) when all 3 furnaces are calling for heat, the primary flow rate is 10 GPM and the secondary flow rates are:

    zone 1 (WTAHX) = 2.5 GPM
    zone 2 (WTAHX) = 3.33 GPM
    zone 3 (WTAHX) = 4.17 GPM

    So, if I understand you correctly, "full flow minus one load" (i.e. minus zone 1) = 7.5 GPM

    referencing http://www.engineeringtoolbox.com/pressure-loss-steel-pipes-d_307.html

    7.5 GPM through 1-1/2" steel pipe is ~1.24 f/s
    7.5 GPM through 2" steel pipe is ~0.74 f/s

    Additionally, I am planning 4 other zones:

    DHW + sidestream towel warmer with monoflow tees and trv (constant flow, entire heating season)
    pool (shoulder seasons)
    spa (entire heating season)
    garage fancoil (only around design conditions which is 18F)

    I guess I need to calculate these additional flows but it looks like I'll be building the manifold using 2" tees and nipples to try to hydraulically separate the secondary loads.

    Am I on the right track? Also, where do you get the 2 ft/s because I referenced 4 ft/s from Caleffi?

    Thank you
     
  24. Antman

    Antman
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    Sep 27, 2015
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    Could I please get suggestions/feedback on my thoughts for boiler and primary pumps:

    P1 --> 0013-VDTF3 (cast iron delta T) for house 1 primary in Garn Barn --> 10GPM@5.57FOH
    P2 --> VT2218-HY1-4C1A00 (cast iron setpoint) for fancoil in house 2 --> 3.5GPM@3.96FOH
    P3 --> 0010-VSSF3 (stainless steel variable speed setpoint) for the Garn boiler --> up to 18GPM@4FOH (only uses S1) setpoint setting ~180F

    OR

    P3 --> 0013-VDTSF3 (stainless steel delta T) for the Garn boiler --> up to 18GPM@4FOH (uses S1 and S2) dT setting 5F
     

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  25. leon

    leon
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    Feb 3, 2013
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    With three circulators as you suggest in the drawing your going to
    have issues with the point of no pressure change even though you
    do not have an air scoop and lots of air bubbles even though its an open system.

    A little help from a B+G or TACO sales rep will solve this for you if you fax them a
    drawing or drawings of your system.

    Your trying to circumvent basic laws of hydraulics with your design and your going to lose circulators.
     

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