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Question about our indirect dhw and non-heating season

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Cyclist77
Cyclist77 Member Posts: 267
in Domestic Hot Water

Last fall we installed a Weil-McClain CGa3 and a Weil-McClain I direct dhw tank. We have radiant floor heat so I am aware of running the boiler at a high enough temperature to avoid condensing. But in the non heating season when the only time the boiler fires is for dhw that is set at about 130F am potentially looking at a problem?

Comments

  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,777
    edited 6:08PM

    Your boiler should be set to fire at ~180F when making DHW.

    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
  • bburd
    bburd Member Posts: 1,316

    There are two different temperature settings involved here. If the indirect hot water tank thermostat is set at 130°F, the boiler must produce water hotter than that to transfer heat to the tank at a reasonable rate.

    Usually with an indirect tank the boiler is set up "cold start" to fire only on demand from the tank in the non-heating season, with a high limit of 180° F. That will allow the boiler to come above condensing temperature on water heating cycles.

    —
    Bburd

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