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Thread: what's up with the flow

  1. #16
    DIY Senior Member zl700's Avatar
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    No like I said and provided the link, change the piping and add the secondary pump external to the heating box.

  2. #17
    DIY Member rrekih's Avatar
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    I have talked to Navian and they are willing to supply the Armstrong E9B pump as the spec's are showing this pump.
    With that if you look at page 11 this is how I have my system plumbed. As a closed loop system.
    So before I change everything I will try the Armstrong and see if it does the job. I am only doing about 1500sqare ft. of space.

  3. #18
    DIY Senior Member zl700's Avatar
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    The Navien drawing shown is an example of design. When drawn it couldnt possibly know all system installation perameters (length, # of loops, # of bends, heat load, .......).
    A hydronic system designer with experience and knowledge always trumps system designs. For example why do you think they show the install also that I suggested you use?
    You wont like the Armstrong pump once you get it installed
    Good luck

  4. #19
    In the trades Dana's Avatar
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    Quote Originally Posted by rrekih View Post
    I believe that I don't need a buffer tank as the heat system is fully modulating.
    17,000 to 160,000btu's
    . From what I understand a buffer tank is to keep the boiler from short cycling.
    The connection stubs are 3/4in for the out and in of the heat system. I have just kept the same size.
    The supply and return from the manifold etc. is 1in. and I have kept that the same.
    One thing though I have put in a PRV in the 1in supply to the manifold, would this restrict the gpm?

    Thanks for your response.

    You have it broken up into 5 zones- just how much mass do you have in your smallest zone, and how big it it's average heat load relative to 17KBTU? (17K is more than half the design-day load at my house, and many times the heat load of my smallest zone.) Odds are NONE of your 5 zones have a 17K heat load, even on design day.

    If you're not getting at least 5 minute burn (or 10 gallons through the Navien) at a time, you're losing efficiency. Every ignition and flue purge cycle takes it's toll... (Which is why in the real-world a condensing Navien rarely breaks 80% average efficiency in a residential hot-water only application.)

    Buffer tanks have very low head, so using a buffer as the hydraulic separator you can use small pumps on the boiler loop and get all the flow you need, and properly set up with the gpm & temp dialed for your design heat load, the Navien will modulate well on the average load working with the mass of the buffer. It'll likely reduce the number of burn cycles in a 5 zone system by half, and set a minimum burn based on the raw mass of the working volume.

  5. #20
    DIY Member rrekih's Avatar
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    The design on page 12 shows a hook up for a open loop system.
    The one on page 11 is closed loop, this still could be done as a primary / secondary system.
    I will listen to what you have to say about the armstrong pump, maybe this is why they don't use these anymore.
    You haven't said anything about a buffer tank as in the post after you by Dana, what are your thoughts on this.

    So a buffer tank would be added to the primary / secondary system?
    The primary system would supply the buffer and the secondary would draw off of it?
    Right now I have 5 cct's all running 250' to 300', I will be adding 3 smaller cct's in the near future.
    What size would I make the buffer?

  6. #21
    DIY Senior Member zl700's Avatar
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    You wont need a buffer tank with your setup, it looks like you have a CR240 which turns down (modulates) to 17,000 BTU minimum, and there is enough mass in the piping heatbox and demand in the tubing to not warrant that. Buffers are mainly used when heating loads are smaller than minimum firing rates resulting in cycling of burner.

    While 5 zones is mentioned it appears they are not controlled, it is probably more like 5 loops into 5 different areas.

    Buffers never hurt, but experience tells me here its not really necessary here

  7. #22
    DIY Member rrekih's Avatar
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    They are not controlled at this moment but will be when I get this sorted out. Probably there will be 3 or 4 control zones, depending on how I want to the basement.

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