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Please have a critical look at my Garn Plumbing

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by cmittlesteadt, Nov 29, 2011.

  1. cmittlesteadt

    cmittlesteadt Member

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    Hi All,

    Well, the Garn was delivered a week ago and it's time to start plumbing it into our existing LPG boiler hydronic system. Here's a little of the backstory. We built a new building detached from the house. The new building houses the Garn and in a separate room is an art studio with a full bath. We installed hydronic coils in the slab. Our existing house is heated with a combination of staple up and slab hydronic coils via an LPG water heater. We want to use the Garn to heat everything and provide DHW for everything. I plan to install an on-demand LPG water heater for DHW in the outbuilding as well as to provide some heat backup to prevent the Garn and the outbuilding from freezing should we go away for a week or two in the winter. I trenched in about 110' of 1-1/4" HePex lines for connection between Garn and Polaris (house water heater). I also put in two 3/4" HePex lines for cold and hot water supply from the house to the outbuilding, but I probably won't use the hot water line due to the distance and the time it would take to actually get hot water from the faucet in the outbuilding (sourcing it from the house).

    All this being said, I'm very novice at this and I fully expect that the attached plumbing layout has many problems. Please have a look and offer your suggestions before I start to cut pipe and solder.

    Thanks!
    Chris

    Attached Files:

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  2. bpirger

    bpirger Minister of Fire

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    Just a few quick comments....to get the ball rolling.

    1. How do you control the temperature of the water into the studio floor? You don't want to put 180 degree water from the Garn into the floor....
    2. After the HX, looks like whenever the primary loop is on hot water is passing through your indirect tank. How hot do you want the indirect to get? Even with the mixing valve on the output, seems like you don't want your indirect heating up to 180 say when the house radiant is calling for heat....
    3. Did you intend to take the supply manifold for the studio floor from the "cooler" water in the primary loop? Then the cool water from the studio floor goes into the "hot" part of the primary....so then you are delivering "cooler" water to the HX. I'd think you'd want to maximize the hot water through the HX, and then pump the cooler water downstream of the HX into the radiant manifold supply for the studio. But you also want to control the temp in the studio (and house) floor. I use mixing pumps...many use valves.

    4. Are you cirulating DHW through the heat exchanger, the floor in the house? I guess I don't understand the pipe coming out of the tanguki water heater. Typically one doesn't want to circulate potable water through the flooring and all....

    OK, already interupted a zillion times, I'll let this go....
  3. Como

    Como Minister of Fire

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    I am on my lap top and the schematic is not so visible to my old eyes.

    I will also repeat some of what has been said.

    I assume you also get very cold, we, have a storm coming in and it will be minus something on Thursday.

    So we have two buildings, one withe the Garn a 100 ft or so apart.

    You have run heat lines and water lines between the two.

    What did you use for the hot water and heat lines by way of insulated pipe, Microflex or what? I guess it does not matter for the hot line but that stuff is expensive for something you might not use.

    It seems that the distribution system in the Studio is on the wrong side of the Hx? I was just wondering how much direct heat from the Garn will go into the Studio.

    I presume you have a Glycol water mix in the lines, water in the Garn, but the way you show it there is just water going around the Studio.

    Does the water heater in the Studio have two inputs and outputs? You need to keep the DHW separate.

    I am not familiar with the Boiler in the House, I would have thought you needed a water tank with heat exchanger to pre heat from the Garn and then top if required by the Polaris.
  4. cmittlesteadt

    cmittlesteadt Member

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  5. cmittlesteadt

    cmittlesteadt Member

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    Yes, we get down to -20 or -30 several times throughout the winter. I spray foamed all of the lines between the house and studio. They are embedded in about 6' of closed cell foam. They should all be quite well insulated.

    The radiant manifolds for the studio are using the water directly from the Garn, pre HX. It's a closed loop system, so I'm thinking that should be acceptable. I too wonder how much radiated heat from the Garn will be present in the studio. It's set up not to rely on it, but I think that there will be plenty....

    The Garn will have it's normal cocktail of plain water and anti-corrosive chemicals in it. The loops for the studio slab will also share this water. There is no glycol anywhere in the system. The lines run between the buildings will have water only.

    In practice, the DHW will be separate via valves regarding the studio water heater. I hope to set the valves up in such a way as to use the water heater to prevent freezing in the studio when we are gone for more than a day or two.

    The Polaris is an interesting unit. Cold water supply, DHW out, Heating system supply and return connections. All connections share the same tank. No coils. It's been great for our radiant and DHW for 10 years now. I'm just thinking that we should be able to heat the water in the tank to a temp where the Polaris won't kick on very often.

    Thanks for your help!
  6. Como

    Como Minister of Fire

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    What happens to the water in your lines when you leave for a few days, there seems to be no mention of how you will heat them?

    The Garn is an open system, so the Studio would be as well.

    I would be very uncomfortable using the Takagi the way you mention.
  7. Jim K in PA

    Jim K in PA Minister of Fire

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    Chris - after just a quick glance, I see a few problems. I also have some difficulty reading some of the details on the drawing due to its small size, but look at the following:

    1 - flow to/from GARN - it looks like you have the pump pulling from the lower bung and returning to the upper bung. This is the opposite of how it should be connected. Pull the hottest water out at the top, and return at the bottom of the tank.
    2 - flow through your HX - you have it drawn with parallel flow, rather than counter flow. To maximize heat tranfer across the HX you need to plumb it counter flow.
    3 - the rest of the system is a mix of plumbing that will not likely send water where you want it. You need to put the studio WH on the manifold like the other loads. For the house loads you need to set up another set of manifolds, or build it as a primary/secondary scheme. In fact, I would set up the GARN side with P/S, and send water where you need it on the secondary loops.

    Get a copy of Holohan's books "Pumping Away" and "Primary/Secondary Pumping Made Easy". They are great primers on plumbing hydronic heating systems.
  8. cmittlesteadt

    cmittlesteadt Member

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    Hi Guys,

    Thanks a bunch for the observations and suggestions. I've given it another shot incorporating your suggestions. Can you please have a look and see what you think now?

    Thanks again!
    Chris

    Attached Files:

  9. bpirger

    bpirger Minister of Fire

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    Much better! Some quick thoughts...

    On the primary loop coming out of the Garn, you have the feed to the manifold for the studio downstream and the return upstream, I think you want to reverse these. In other words, you want the hottest water going to the manifold, and the cooler water return from the manifold "downstream". Else you'd be sending your just returned cooler water back to the manifold. For a low temp radiant system it might not matter....but you still want to put the hot water where it should be.

    Flows through the HX are opposing....good!

    I still don't like the idea of plumbing DHW through the radiant loop.....I tihnk that takes a risk of critters....in a loop with low flow, sitting all summer, growing critters...and then it ends up in your child's glass of water....but sounds like you are willing to take this risk.

    You also need a mixing valve on the house manifold I'd say, to control the house radiant temp....though I assume your method of doing this would be the aquastat on the Polaris controlling the pump through the HX. Turn it on for heat, turn it off when warm enough. But you water in your floor will always be that temp then....

    Personally I'm not a big fan of unions, they always seemed to leak to me, but with the proper Locite 55 or whatever, they would be ideal.

    Make sure your Garn hot water is taken from the top feed off the Garn...and return to the bottom.

    Having strainers around your HX is a good thing, so that you don't get crud inside the narrow passages. You have a strainer in the garn primary....which is fine...but stuff can flow into your HX and get stuck. Webstone has some nice integrated purge valves with a boiler drain that allow you to easily flush out the HX without having to remove anything....probably $50 a pop.

    Air scrubbers are a good thing...not sure if you have any of those anywhere.

    Are you going to get enough flow from the Garn loop into the studio floor manifolds with just that pump in the floor loop? Not sure you will suck in the water you want through the mixing valve from the Garn loop. Typically in a primary/secondary arrangement you'd have a pump circulating the water in the floor in the studio, and then inject hot water into that loop with another pump in the secondary lines. You might get some flow out of the studio floor and into the Garn, but I don't think you will get all the hot water to the studio floor you want. But I don't use mixing valves, I use mixing pumps, so maybe it will work....??? Just seems like you don't have a real way to direct hot water to the studio floor. I'd think the head loss through the mixing valve would be much higher than the return tee, so most of the water would go back to the loop...and not sure you'd get enough hot into the loop. But then the mixing valve would open more I guess, reducing the head, and perhaps balance better....just not sure.
  10. cmittlesteadt

    cmittlesteadt Member

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    Corrected drawing for proper flow for Studio heating manifold... DOH!

    Attached Files:

  11. BHetrick10

    BHetrick10 Member

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    I am in no means a boiler installer. . . Just thought I's say that first in case i am off my rocker :cheese:


    If I am looking at your drawing correctly I think your Circ pumps are on the hot side. I believe they should be on the return side pulling the water not pushing.

    Any thoughts. . .

    I have a Garn I am trying to figure out as well. I believer your set up with you water heaters and such makes yours a lot more difficult than mine.


    I am still at the beginning. I cant get anyone to help me do a BTU calc on new construction.

    Best of luck
  12. bpirger

    bpirger Minister of Fire

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    Pumps are rated these days to over 220F, so putting them in the hot water should be fine. I think most do these days, pumping away from the expansion tank, which is usually just outside the boiler. now, we don't have one of those with the Garn open system. You do have to assure you have the NOPISH (similar!), look in the Garn manual. Otherwise I think the hot water can flash boiler at the pump, causing cavitation...it's in the Garn install manual.


    I think what you have now is WAY better than intially. I still don't like that DHW use though...I'll always "complain" about that. But I think what you have should work...
  13. Sawyer

    Sawyer Minister of Fire

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    Supply water from boiler should go into the mixing valves, return water tee'd to cold side of the mixing valve, mixed supply water out to the supply manifold.
  14. jebatty

    jebatty Minister of Fire

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    My recollection is that mixing valves are designed to operate by water being pulled through the valve rather than pushed into the valve, which also then indicates that the circulator needs to be on the return side of the boiler.
  15. Sawyer

    Sawyer Minister of Fire

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    Missed that Jim, good catch. I automatically assumed the water was being pulled through the valve rather than looking closely as you did.
  16. Como

    Como Minister of Fire

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    I would prefer to see the HX with the Garn in the Studio Building.
  17. cmittlesteadt

    cmittlesteadt Member

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    What would be the advantage of having the HX in the Garn building instead of in the basement of the house?

    Thanks!
    Chris
  18. bpirger

    bpirger Minister of Fire

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    Less distance for the water to travel, presumably the hottest water, and less loss in the underground piping....
  19. cmittlesteadt

    cmittlesteadt Member

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    Rev. 4 -

    Moved pumps to cold side of circuits, moved HX near Garn, arranged mixing valves to operate with water pulled through rather than pushed through them.

    I do understand the concerns with the radiant water being mixed with the DHW in the house. We've used it that way for 10 years now. I do intend to separate them, but that needs to wait for another time. I need to get the Garn running first, then I can tackle some improvements on the House distribution side.

    Any other issues, guys? The time is drawing near....


    Thanks a bunch!

    Chris

    Attached Files:

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