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Thread: Circuit Setter

  1. #1
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    Sep 2003
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    Circuit Setter

    I have ran across a few circuit setters on hot water piping to air handlers as well as hw and cw unit ventillaters, im not familiar with the valve what exactly is their purpose and how do they work? Thank You

  2. #2
    Join Date
    Apr 2002
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    They are a balancing valve that allows you to set and measure the water flow rate through a coil
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

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  3. #3
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    Nov 2007
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    A circuit setter is basically a calibrated valve with a known Cv (Velocity Constant) at each setting. Some have a scale from 40-100%. Large balancing valves have a rising stem from 0-100%.

    To calculate flow, you either need to buy a test gauge from the valve manufacturer or buy a gauge adapter. This is similar to a needle used to pump up a football. On either side of the circuit setter is a brass cap that can be removed. A pressure gauge with a gauge adapter is inserted into this P/T port, also called a Pete's Plug. Take a pressure reading on either side of the circuit setter, subtract the smaller from the larger and you will get the pressure drop across the valve in psi.

    You will then need to find the curve chart for that particular valve. Most are available on the manufacturers internet site. On the chart you will need to plot the valve position indicated by the valves calibrated scale and the pressure drop. The chart will give you GPM. If feet of head are shown on the chart instead of psi, just multiply psi X 2.31 to convert to feet of head.

  4. #4
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    Cv isn't velocity constant. Just don't like the sound of that since it is not related to velocity per se. It is the flow coefficient or valve coefficient and relates pressure drop and flow rate. The Cv value tells you the amount of water at standard conditions in GPM that will flow through the valve at a pressure drop of 1 psi.

  5. #5
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    Quote Originally Posted by hvacconsultant View Post
    Cv isn't velocity constant. Just don't like the sound of that since it is not related to velocity per se. It is the flow coefficient or valve coefficient and relates pressure drop and flow rate. The Cv value tells you the amount of water at standard conditions in GPM that will flow through the valve at a pressure drop of 1 psi.
    You are right, I used the wrong terminology, but the rest of my post holds true.

  6. #6
    Join Date
    Feb 2006
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    I've never heard it explained that simply. That would mean a 4 Cv valve would flow 4 gpm @ 1psi drop. Would that mean it could flow 8 gpm @ 2 psi drop ? It can't be that easy. --- gman

  7. #7
    Join Date
    Nov 2007
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    388
    Quote Originally Posted by gman994 View Post
    I've never heard it explained that simply. That would mean a 4 Cv valve would flow 4 gpm @ 1psi drop. Would that mean it could flow 8 gpm @ 2 psi drop ? It can't be that easy. --- gman
    You're right...not that easy. The formula is for fluids is-

    Cv^2*Delta P/SG=Q

    Where
    Cv = Valve Coeff
    Delta P = Valve Pressure Drop in PSI
    SG = Specific Gravity of the flowing fluid (water=1)
    Q = Flow in GPM

    Keep in mind that the valve Cv is usually given is in the full open position. Some Mfr's will have the Cv for other positions. Steam flow uses a different formula that you can find on the internet.

  8. #8
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  9. #9
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    Dec 2009
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    Is a combination balancing and shut off valve the same thing as a circuit setter? If not, what is the difference?

  10. #10
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    Jun 2006
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    Quote Originally Posted by Hydestone View Post
    Is a combination balancing and shut off valve the same thing as a circuit setter? If not, what is the difference?
    I've never seen a combination balancing/shut off valve. You have a link?
    I've seen combination balancing/flow rate/check valves.

  11. #11
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    Dec 2009
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    There is a note on a schematic that says combo balancing shut off valve. I am not sure if that just means a circuit setter or if that is another way to balance.

  12. #12
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    if it has a check valve as well it is a 'triple duty valve'
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  13. #13
    Join Date
    Dec 2009
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    13
    Is it possible to balance a hot water coil in a Titus CV unit using a ball valve only?

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