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Crossover bridge balancing valves and flow check valves

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SuperTech
SuperTech Member Posts: 2,205
I'm going to change the near boiler piping on my boiler to a variable speed injection pumping setup. Thanks to all the help everyone gave me on my last thread I am much closer now to beginning the alterations.

I'm stuck on what to do with the crossover bridge. Obviously the supply side will have the variable speed pump, and Tekmar recommends installing a globe valve on the return line for balancing. In Dan Holohans book he recommends flow check valves on both sides of the injection loop.

My question is about the balancing valve. I don't have a globe valve but I do have three types of balancing valves. I have the standard old fashioned type that you might see on a split loop as well as a Taco circuit setter balancing valve and a Caleffi QuickSetter with flow meter. Can any of these be used to balance flow on the crossover bridge?

Also what is the best type of flow check valve to use? I plan on using the IFC on the circulator but I don't know what to use on the return line. Would a 17 CV Caleffi flow check be adequate? What about a cheap Honeywell flow check?

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  • hot_rod
    hot_rod Member Posts: 22,479
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    Have you determined the flow rate across the "bridge"?

    The circulator should have a check in it? One checks in the circulator should be adequate, a balance valve in the other leg would provide enough flow resistance to prevent any ghost flow. Certainly no harm in adding an additional check.

    Inside that Caleffi check is the exact same check assembly used in circulators. It is a very flow friendly, soft seat, low cracking hydronic check.

    Really any of those balance valves are fine, it is usually a one set valve, not something you will be constantly changing or adjusting.

    Unless you already have one, the Caleffi 132 Plus has a check and temperature gauge, so you could balance by flow to temperature.

    It is intended for DHW so it is low lead.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    SuperTech
  • SuperTech
    SuperTech Member Posts: 2,205
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    The flow rate is variable across the bridge isn't it? I'm guessing that the maximum flow should the same as the system flow rate. I used a formula with the design delta T and BTU rating of the boiler in Dan's book and came up with 7.48 GPH. 1" pipe should be fine for that and it's also one size smaller than the boiler loop and secondary.

    I'm glad I can use the QuickSetter, it's a sharp looking unit. I don't know how I missed seeing the plus model, that looks even better and would save me from buying a separate flow check and temperature gauge.

    This is what I have so far. The first picture is my plan for a boiler loop. The wye strainer is where I am putting my Supervent and water feed/tank.

    The next is the beginning of the reverse return manifolds for the secondary. One Alpha pump for all three zones and zone valves is the plan. I just have to figure out the injection lines with thermal traps and how to tie it all together with the existing piping. Do you think this will work? Or do I have to go single pipe with circs for each zone?

    @hot rod_7 Your have been such a great help with everything, I can't thank you enough.

    I saw a pinnacle boiler at work today with a setup similar to what I am considering, but that boiler didn't have any variable speed control
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,646
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    Is your boiler on a stand with a filing cabinet under it? Cool!
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • SuperTech
    SuperTech Member Posts: 2,205
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    > @Solid_Fuel_Man said:
    > Is your boiler on a stand with a filing cabinet under it? Cool!

    Nah, that's just some junk piled up in my basement.
  • hot_rod
    hot_rod Member Posts: 22,479
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    What flow rate will you adjust the balance to? Max. flow rate?

    Usually injection mixing is used when the boiler runs a high temperature and the distribution much lower. You determine how many gpm of a fixed SWT needs to inject into the low temperature side, determine the head, select a circ as close as possible, then balance to get pithing a fraction of gpm accuracy.

    In your case you want to move the entire gpm thru the crossover, running boiler and distribution at the same temperature?

    Or modulate the boiler and distribution at different variable temperatures?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream