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Distribution Advice sought....

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by kuribo, Feb 18, 2013.

  1. kuribo

    kuribo Feeling the Heat

    Joined:
    Dec 10, 2007
    Messages:
    255
    Loc:
    SW WI
    II am currently designing the heating system for my new home and am hoping for some input from some of the experienced installers/users on this site. Here is an outline of what I am planning:


    I have a Econoburn 200 which I will put in its own outbuilding, 50' from my house. I will trench in the 1 1/2" boiler return and supply, then spray foam. In my basement, I will have 2 500 gallon propane tanks, insulated.

    I will feed the boiler into a small tank, like a hydraulic seperator, then plumb off the tank to my 2 basement zones, 2 upstairs zones, and storage tanks. All emitters are in floor, hydronic (concrete). I need higher supply temps upstairs (120F) than downstairs (110F) due to heat loads and pex spacing. The house is a timber frame insulated with spray foam. If it weren't for all the windows, the heat load would be rather small. As it is, in Wisconsin, on a -25F design day, I calculate a heat load of 70,000btu/hr. The upstairs is roughly 2200 square feet, the walkout, full basement, about 2500 sq ft. The house has a lot of mass and takes a day or two for the temp inside to change much with changes outside.

    I have done a lot of reading and research and am leaning towards the primary/secondary system, using a small tank as a hydraulic separator. I will feed the boiler into the tank, then plumb off the tank to my 2 basement zones, 2 upstairs zones, and storage tanks. All emitters are in floor, hydronic. I need higher supply temps upstairs than downstairs due to heat loads and pex spacing.

    I understand the need for boiler protection and will most likely use one of the packaged loading valves in the primary loop.

    Now, where I am confused is how to best arrange my secondary system. I see four likely scenarios:

    1. Separate circulators and zone valves for each of the 4 zones.

    2. Separate circulators and modulating mix valves for each zone.

    3. A variable speed circulator feeding all zones with zone valves for each zone.

    4. One variable speed circulator and zone valves for basement 2 zones and one variable speed circulator and zone valves for the 2 upstairs zones.


    I understand the the basic pros/cons of zone valves, one circulator versus multiple, etc. But wonder if the specifics of my system would cause one design to be favored over another. I am leaning towards the single variable speed circulator and zone valves due to electric costs, but like the redundancy of the multiple circulators.

    Would greatly appreciate any advice, especially if there is yet another secondary system I haven't mentioned that would be better than those I have mentioned.

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  2. ewdudley

    ewdudley Minister of Fire

    Joined:
    Nov 17, 2009
    Messages:
    1,746
    Loc:
    Cayuga County NY
    With radiant loads you can draw to the mixing valves directly from storage, no separate buffer, hydraulic separator, separate primary-secondary required. Radiant loads automatically minimize return temperature to storage so it's pretty fool proof. The boiler then feeds to storage, so storage is your hydraulic separator.

    If it's not too late it would be great to have a DHW coil in the upper tank.

    If you really need two radiant temperatures only ten degrees apart then as you suggest: two mixing valves, two constant head pumps (Grundfos Alpha or Wilo Stratus) and as many zone valves as required. For all the difference it would make it seems like just one radiant temperature would be sufficient, so then all you'd need is one mixing valve and one constant head pump. Pumps are pretty reliable and easy to change so I can't see putting much weight on having multiple pumps for redundancy's sake.

    For zone valves I don't have enough experience to recommend on type over another for the long haul, but of the ones I've used I must say the Taco EBV (or whatever they're calling them now) are pretty slick.
    Taylor Sutherland likes this.
  3. BoilerMan

    BoilerMan Minister of Fire

    Joined:
    Apr 16, 2012
    Messages:
    1,604
    Loc:
    Northern Maine
    EWD got to it first! Radiant makes storage piping and configuration easy, nice low return temps for max btu's from storage. Curious as to where you can find 1.5" lines to/from boiler? PEX? Taco I-series valves with outdoor reset work well for what you want to do. Although I've done jobs sucessfully with simple fixed-temp mix valves with satisfactory results. I'd do reset in slab though.

    BTW, nice looking house! Old world European look, I like it.

    TS
  4. kuribo

    kuribo Feeling the Heat

    Joined:
    Dec 10, 2007
    Messages:
    255
    Loc:
    SW WI
    Thanks for the replies.....

    So just pipe directly from boiler to storage tanks, from storage tanks to a loop with one variable speed pump feeding a mix valve and 4 zone valves...Simple enough.

    Appreciate the help very much...

    By the way, the house is actually a traditional Japanese farm house, adapted to the Wi climate.....

    And the 1 1/2" supply and return lines to be trenched in from the boiler to the house are rehau 1 1/2" pex.

    DSCN2232.JPG DSCN2217.JPG
  5. Bob Rohr

    Bob Rohr Minister of Fire

    Joined:
    Jan 9, 2008
    Messages:
    798
    Loc:
    SW Missouri

    I'd run a single temperature system. Unless the temperature requirements are more then 20 degrees, stick with one temperature. A single ECM circ could easily move the 70,000 design day load. The delta P circs work nicely with zone valves.
  6. kuribo

    kuribo Feeling the Heat

    Joined:
    Dec 10, 2007
    Messages:
    255
    Loc:
    SW WI
    Another question:

    What sort of hardware do I need in each branch after I tee off the supply line? I am thinking tee, then shut off valve to isolate, then zone valve, then another ball valve at the distribution supply manifold and another at the return manifold, then another ball valve at the return before the tee into the return line. So each branch line to would have a total of 4 isolation/shut off valves and a zone valve. Anything else needed?

    Thanks again.

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