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Indirect DHW Connection Choices

dcwittlo
dcwittlo Member Posts: 11
edited August 21 in Domestic Hot Water

I am an amateur with an engineering background (BSEE) but I need some help deciding how to connect my Indirect DHW Tank to my new hydronic system. I have included a couple of drawings of my plans. The manual for my Weil-Mclain EcoTec 110-H mod-con boiler shows one way but the manual for the Weil-Mclain Aqua-Plus DHW shows something different. Are these connections correct/workable? Is there a "best way" to connect this? Any suggestions or criticism is welcome. By the way, I have read practically every Caleffi iDronics article and I have read Dan Holohan's "Primary/Secondary Pumping Made Easy" book. Nevertheless, there are a lot of factors to consider and there is no substitute for experience (of which, I have none).

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Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 16,283

    I think they all will work.

    In dwg #3 you would have to be sure the diverter valve is sized properly. This drawing will give you DHW priority. as will drawing #1 sending the hottest water to the indirect first.

    Drawing 2 keeps everything nice and balanced.

    All things being equal I guess I would go with #1.

    A lot depends on your hot water demand and the boiler size. If you need HW priority drawing 1 & 3 provide that. Drawing #2 gives the indirect a mixed water temp (lower temp)

    Without knowing more about the system I would go with #1

    Alan (California Radiant) Forbesdcwittlo
  • dcwittlo
    dcwittlo Member Posts: 11

    I am torn between drawing #1 and #3 because a 1" diverter valve seems to cost two-thirds as much as the circulator pump would. Also, would dwg #3 require a (spring-loaded) check valve somewhere in the system to prevent ghost flow?

  • dcwittlo
    dcwittlo Member Posts: 11

    It might be worth noting that I am remodeling my house at some point and I want to change from baseboards to radiant floor.

  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,210

    A check valve on the system return to the LLH wouldn't hurt.

    https://www.supplyhouse.com/Caleffi-NA51376-1-1-4-Press-Serviceable-Inline-Check-Valve-Low-Lead

    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • HVACNUT
    HVACNUT Member Posts: 6,239

  • HVACNUT
    HVACNUT Member Posts: 6,239

    They all work, however the first drawing shows the indirect piped before the space heat manifold, so with that design the DHW circulator and controller gets wired into the boiler.

    The second drawing requires the DHW circulator AND the boiler circulator.

    The first drawing is typical. The second drawing will NOT turn off the space heat pumps from the zone panel if there is one. Therefore no priority, if that's a big deal.

  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,210
    edited August 3

    HVACNUT said: “The first drawing is typical. The second drawing will NOT turn off the space heat pumps from the zone panel if there is one. Therefore no priority, if that's a big deal.”

    Won’t the zone valve control turn off all the heating zone valves and open the DHW zone valve in priority mode?

    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab

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