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Zone Valve: Always wondered.....

adambuild
adambuild Member Posts: 414
in THE MAIN WALL
Yesterday we had to replace an Erie zv and I was surprised how large the opening was inside the valve that the water flows through although not full port. The openings in the Honeywell zv's that we usually use are much smaller. I actually checked a Honeywell 1" zv yesterday out of curiosity and the opening inside was about 3/8"! Why so small? Is bigger better/faster response? What's the reason?

Thanks, Adam

Comments

  • hr
    hr Member Posts: 6,106
    Most valves have a Cv listing

    that indicates GPM flow. Some manufactures, Caleffi for one, offers zone valves in various Cv's.

    If you use a zone valve for an indirect tank water heater always chose the one with the highest Cv rating.

    hot rod

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  • Brad White
    Brad White Member Posts: 2,399
    Hot Rod is correct as usual

    The reason you may want a smaller Cv is for tighter control to a setpoint in a modulating control valve. This allows more proportional response to a change in the variable being controlled.

    Imagine trying to control 0.50 GPM using a 1/2" reduced-port valve with a 1.2 Cv as opposed to controlling 0.50 GPM using a 3" butterfly valve..... you can see how a little movement on the 3" valve (with a higher Cv you bet!) means a lot more flow...

    As Hot Rod said, with an indirect or other on-off/open-closed application, you want a larger Cv. You are not trying to modulate the flow but rather give it a huge "Yes" or a huge "No".
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"



    -Ernie White, my Dad
  • ALH_4
    ALH_4 Member Posts: 1,790
    head loss

    Yep, the Cv rating is very important. In many zone valves, a larger pipe size does not necessarily have a higher Cv rating.

    head loss in feet = (1.52*gpm/Cv)^2
  • Weezbo
    Weezbo Member Posts: 6,232
    We askrd the Honeywell rep if

    or when they would get a 1' with a higher cv ... they said they are definitely considerig it ..maybe Bill can tell us when these might be available for domestic hot water indirects.
  • jp_2
    jp_2 Member Posts: 1,935
    hydraulic force

    i would think the reason for the smaller opening is to reduce the force against the valving mechanism, reduce valve slamming and wear? just a guess. psi x sq inches = force
  • Unknown
    Unknown
    One of the problems with

    a low CV rating with a High GPM pump is noise on shut down. It is there fore important to match the zone valve with the flow rate to insure quiet operaion.
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