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Veritable speed circulator and Design check

garyagarya Posts: 7Member

This is my first radiant design so would appreciate input especially sizing a variable speed circulator for zones 1-3 (where the incorrect Taco 007 is now). Considering Taco VR1816 Variable Speed circulator. Building is 2 story in Seattle WA on slab over 1.5” insulation, heat source currently 75kbtu propane water heater. Two yellow valves between zone valves are for pressure gauge isolation. Nothing has been soldered open to changes.

----- Circuit 1; zones 1,2,3, variable speed pump
Zone 1; RV bay 20'x35'x16’ slab; 85’of 3/4” copper equivalent common piping with three 220' 1/2” pex loops in slab, heat loss 10kBTU
Zone 2; Living room 12'x35'x8’ slab; 70’of 3/4” copper equivalent common piping with two 220' ½” pex loops in slab, heat loss 6kBTU,
Zone 3; Bathroom; 90’of 3/4” copper equivalent common piping with one loop 100' ½” pex between joists, towel rack, heat loss minimal

----- Circuit 2; zone 4, single zone, Grundfos UPS15-58FRC 3-Speed Circulator
Zone 4; 2nd story 14’x35’x8’;80’of 3/4” copper equivalent common piping with three 320’ 1/2” pex loops between joists under hardwood floor, heat loss 6kBTU



  • garyagarya Posts: 7Member
    Schematic for system. The real question is sizing the veritable speed pump?
  • hot_rodhot_rod Posts: 11,624Member
    I think you have your air and dirt separators swapped? The air sep should be in the hottest supply from the boiler, dirt usually on return.

    The circ should run in a delta P mode for the zone valves. Determine the total gpm required, look at the pump curve and set so you get adequate flow. The pump will modulate up and down as the zone valves open and close. Usually .5 to .65 gpm per 1/2" loop, add em up.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • garyagarya Posts: 7Member
    Thanks hot rod, the separator and filter will get moved up to boiler. Also the estimate of about 4gpm flow is helpful, just seemed low when I did the numbers.
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