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Why does my zone valve use 40v transformer?

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drosner
drosner Member Posts: 53
in THE MAIN WALL
I’m replacing my taco circulator zone control and I have one zone where a prior owner/contractor put a zone valve along with a zone circulator. I’m pretty sure they did that to prevent flow when that zone isn’t on. Either way it works just fine.

Here’s my question…I see they added a 40v transformer and in reading the Taco 571 docs it also indicates to use a 40v transformer. However the specs of the 571 say it’s a 24v device. Why does Taco say to use a 40v transformer to power a 24v valve?

Comments

  • mattmia2
    mattmia2 Member Posts: 13,615
    edited January 2024
    Pretty sure it is 40va 24vac(nominal). 40 va is the power it can provide and is equivalent to a watt but accounts for power factor.
    STEVEusaPA
  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,512
    va stands for volt amp
    vac stands for volts alternating current
    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
  • drosner
    drosner Member Posts: 53
    Uh thank you for clarifying and I feel pretty stupid right now!
  • hot_rod
    hot_rod Member Posts: 25,395
    24V X a .9 Amp zone valve = 21.6 Va
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,512
    drosner said:
    Uh thank you for clarifying and I feel pretty stupid right now!
    Don’t bother. We all have a lot to learn.
    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

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