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In Need of Design Help

Dear Professionals,

I have a 24x40x8 pole building, pex installed in 4"slab with R-10 HD foam under it, R-10 side walls and R-30 in the ceiling.  I have 4 loops of 1/2" pex, the inside of the building is open.  I want to keep the temp @ 70 degrees F, the fuel source will be propane and I will need to have antifreeze.

What are your reccomendations for the *BTU size of the heater, *boiler or hot water heater, *make and model of heating unit.

I understand that the antifreeze is very corrosive, will I need stainless steel, pumps, heat exchangers and manifolds?

I'm sure I have not covered all that needs to be addressed to engineer this project.  Thanks in advance to you all.



  • Ironman
    Ironman Member Posts: 6,868
    More Info Needed

    Have you done a heat loss calculation?

    Where are you located?

    What's the spacing of the tubing?

    Why do you want to use antifreeze?

    Will there be anything else connected to the boiler?

    Is the pex o2 barrier?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Zman
    Zman Member Posts: 7,328
    Condensing boiler

    You should do a heat loss if you have not already.

    I would do a mod/con boiler. You will likely have a low heat load. I would suggest something small. The Lochinvar WHN055 would be worth a look.

    You should absolutely pipe it primary secondary per the manual.

    Out door reset is also a must.

    I think you may have some bad info on glycol.

    Some types are corrosive to aluminum. Assuming you check your chemistry carefully up front and make checking it part of you annual maintenance routine, I don't know of an issue or a need for stainless components.

    The need for glycol is certainly debatable and dependent on the application.

    You will need to derate your circulators and boiler for the glycol percentage you are using.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • NRT_Rob
    NRT_Rob Member Posts: 1,013
    if you have a single zone system

    you may not need primary/secondary. would have to know that the zone flow is appropriate for the boiler and your pump though.

    I bet a small air to water heat pump would beat propane handily in lifecycle costs, if you have any dealers nearby. I just can't justify propane on low temp systems here in maine anymore.
    Rob Brown
    Designer for Rockport Mechanical
    in beautiful Rockport Maine.
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