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check my mixing valve and overall system

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long story short.....
had an existing home moved to my property. put it on a full ICF basement, built a 12x40 addition on the front, and a 24x40 attached garage with a laundry room in the back.
the existing house is adequately insulated, the parts I added are very well insulated and cover about half the original house.

the basement slab is about 2400 sqft with 6 loops of 1/2in pex at about 275ft ea.
the main floor addition is 12x40 (480 sqft) w/3 loops @300ft of 1/2in pex.
the garage is 24x30 (720sqft) w/2 loops @300ft of 1/2in pex.
the laundry room is 1 loop @300ft of 1/2in pex.

I'm hoping this will adequately heat the house for now, and may hook a thermostat to the forced air furnace fan to even out the temp in the house if needed. But I do intend on adding a manifold in the future to feed radiant heating under the floor joists in the original house.

This will have a Aquatherm pressurized outdoor wood boiler @180F/18psi on a primary/secondary loop.

The primary circulator is always on while the boiler is lit, and is about a 120ft loop of 1in O2 barrier pex

The secondary loop is combo of 1" barrier pex and 1" copper as needed feeding a cross12 manifold in the utility room in about the middle of the house running the above listed zones. there will also be a take off for a side arm DHW.

my main question (because all the math is starting to make my head hurt) is the thermostatic mixing valve going into the manifold. if my math is right my loops should take an average of .75gpm ea, so the mixing valve needs to have 9GPM of flow.
with a 5.8CV thermo mixing valve work with the circulator/ system set up?
https://www.supplyhouse.com/Honeywell-Home-V135A1014-1-3-Way-Mixing-Valve-Female-Sweat-Union



Comments

  • Zman
    Zman Member Posts: 7,572
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    Have you done a heat loss calc on the house?

    Your expansion tank wants to be located as closely as possible to the inlet of the circulators, "Pumping Away".

    Ideally, the CV of the valve wants to be ~=to the GPM going through it. If you cannot find one with a high enough CV you may need to upsize the circulator. Personally, I would look at the Taco I series with outdoor reset. The home will overshoot less on the shoulder season days.

    In general, your circs both appear to be on the small size, especially if you may be adding a zone. In the Grundfos line, a 26-99 3 speed would be safer for the boiler loop and an Alpa 2 26-99 would be a better fit for the radiant.


    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Balance
    Balance Member Posts: 7
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    Roughly 25btu per sqft according to the spreadsheet I used
  • GroundUp
    GroundUp Member Posts: 1,924
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    That Alpha 15-55 is never going to push more than about .3GPM per loop in that configuration, and the 15-58 is going to have a heck of a time getting enough BTU to the space and will certainly never supply enough flow to mix that Aquatherm's water jacket. I'm on board with Zman, 26-99FC on the boiler loop (relocated to the hot/supply side, pulling away from the expansion tank) and Alpha2 26-99 on the radiant. A 5.8cV mixer will be adequate with those circs. Also, the 4 gallon expansion tank that comes with an Aquatherm is too small for the volume they hold- it should be twinned or upsized.
  • Balance
    Balance Member Posts: 7
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    These two guys here?
  • Balance
    Balance Member Posts: 7
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    Aquatherm actually specifies the primary pump be on the return side right at the inlet to the boiler
  • Zman
    Zman Member Posts: 7,572
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    That is a generic drawing fora one circ system. With a configuration like yours, you want the circs to be relatively close to each other and "Pumping Away" from the expansion tank. Your system will be easier to purge and your circs won't cavitate if your pressure drops a bit. https://heatinghelp.com/systems-help-center/pumping-away-piping/

    The circs in the post above should work well.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Balance
    Balance Member Posts: 7
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    Last question for now, this is spacifically for boiler protection, is there any reason i couldnt use it to mix the water into the manifold? Has a CV of 10
  • Balance
    Balance Member Posts: 7
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    Nevermind. I guess that one only tempers one way and won't work
  • Balance
    Balance Member Posts: 7
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    Would it be worth setting up 2 thermostatic mixing valves on the supply side to equal the value that I need?
  • Zman
    Zman Member Posts: 7,572
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    The 26-99 Alpha is big enough to overcome a valve with a little lower CV. Unless you are wanting to store heat in your slab between boiler cycles, I would highly recommend this one. https://www.supplyhouse.com/Taco-I100U3R-1-iSeries-3-Way-Outdoor-Reset-Valve-w-1-Sweat-Union?gclid=Cj0KCQiAkNiMBhCxARIsAIDDKNVZfozOK-bcI1UTqopZXdYbiuSwZfxnd_wTTMV1jb5nOIJedROe3ZwaAnOSEALw_wcB
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein