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Do I need a buffer tank?

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brken
brken Member Posts: 1
in Radiant Heating

Hi. I am installing a hydronic system in my basement, and am unsure whether or not I need a buffer tank. LoopCAD shows the modeled slab load at 9,999 BTU/hr, but my Rinnai 90k combi-boiler minimum firing is 15,000 BTU. Will this 5,000 BTU difference be a problem for a slab that is 6" thick, located 6ft. below grade, and is insulated beneath by 2” rigid foam and on the sides by 1.5” rigid foam? My house is located in Seattle, so the basement is cool year-round. All of this information was included in LoopCAD’s calculation. I am primarily concerned with keeping a fairly even temperature for the slab and keeping boiler cycling at a minimum of 10 minutes to extend equipment life. Intuitively, it seems that even 15 minute programmed firing intervals would not produce much heat loss in this large, insulated slab, but I don't know for certain. If I do need a buffer tank, though, should I install it where I was planning to put a SEP-4 hydraulic separator or should I place it before or after the manifold? Any help is much appreciated. If any additional details are useful that I can provide, please let me know.

Comments

  • JMWHVAC
    JMWHVAC Member Posts: 112

    What square footage is the slab and how many loops are in slab and what size/length of tubing? A slab is a tremendous heat sink and if there is enough tubing in the slab there is no need for a buffer tank. A slab will usually receive far more heat than the room requires so control is important.

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