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Internal Boiler Circulator - primary / secondary piping

mtbllp Member Posts: 1
Weil McLane GV-5, Series 1 boiler has an internal circulator pump. I am setting up primary secondary piping. Zones include air handler, baseboards and indirect water heating.

Is the internal circulator pump all that is necessary for teh primary loop? Or, is a second external circulator necessary?



  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,102
    edited December 2021
    The boiler pump will take care of the primary. For your secondary circuit, if you are zoning with zone valves, a second pump is necessary. If you are zoning with pumps, there will be one pump per zone.

    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
  • hot_rod
    hot_rod Member Posts: 22,467
    Is it a GV 90 plus-5? The manual shows how much pump capacity you have to work with.

    if it is an older GV, some of those had a circulator inside for return temperature protection, and still requires a system circ.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream