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plug vs butterfly balancing valves and location

Always size a balance valve for flow not pipe size. They are rarely the same, although I have been on many jobs over the last few years where the design engineer has spec the CBV's the same size as the pipe, Ignorance, laziness, I don’t know. Control valves too, size for flow / pressure drop, not pipe.


  • 6 of one, half-dozen of the other?

    Two questions concerning balancing valves:

    I have a choice between a plug valve (what I called
    a "gas valve" while growing up) and a butterfly valve (cast brass body with thin plate inside adjustable with screwdriver from outside). Which would you use?

    I know globe valves make good balancing valves but I don't like things with rubber washers to deteriorate.

    Second - locate balancing valve on supply or return? Read one place that return location allowed max pressure and better "air management" thru the loop. But the Harrisburg seminar tapes put the fear of God in me concerning throttling pump supply and cavitation problems.

  • Gary Fereday
    Gary Fereday Member Posts: 427

    Mark, I prefer the "cock" type valve for that. The better choice is a B&G balancing valve, or similar. That cheap S/D thing will drive you nuts with leaking. Pump volume is best adjusted by machaining the impeller "on bigger pumps". The small residential pumps can be ok if the valve is placed as far back a possible from the pump inlet (suction). A strainer (large capacity) befor the valve is another way to catch and prevent debrie from stopping the valve. Hope this helps bigugh
  • Gary Fereday
    Gary Fereday Member Posts: 427
    ??? more

    You can check your system. Measure the Amps when running. full load. Compare to the motors specs. High amps=very large water flow. Low amps= very slow flow (deprived water volume) Listening to a pump running, if it sounds like there is gravel or B-B's in it its cavatating.
  • hr
    hr Member Posts: 6,106
    The best balance valves

    will have a tapered cone or plug the moves up and down on a fairly fine thread. Danfoss, Esbe, and Tour Anderson make these.

    A basic ball valve or butterfly are hard to throttle accuratly. The first two thirds of the movment have little effect and suddenly a tiny bit of handle movement makes a big difference at the end of the movement.

    Depends an what you are balancing and how accurate you need to be. The more you spend the nicer the control you will get.

    Robert Bean does an excellent seminar on balance valves if you ever get a chance to catch one.

    I agree that any kind of balance, check, or flow check should be down stream of the pump. Doesn't take much flow restriction on the intake side of a pump to throw them in a tizzy. High head pumps seem especially sensitive to this.

    hot rod

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  • pfitter_2
    pfitter_2 Member Posts: 4
    that depends

    Are you trying to balance the pump or a loop or a terminal unit? What size line are you referring to? If it’s the pump, use a triple duty valve. I like B & G. It should go after the flex connector on the discharge of the pump. For loop or terminal put it on the return, by the main for the former, just after the unit for the later. How critical do you want to be? In these applications B&G circuit setters should be fine but the TA is much more accurate.

  • the particulars

    system still under design - hence the questions

    120k output older Burnham boiler with 1-1/4 primary loop with Taco-005 circulator. I suspect the flow may still be a bit high with this circ so I want to put a balancing valve downstream to use if necessary.

    secondary loop is (will be) a manifold arrangement feeding 2 loops of CI rad and one of CI baseboard. It's driven by a B&G100 controlled by a Honeywell AQ475 outdoor reset. Constant circ and TRVs on all rads/baseboard. I'd like to put a balancing valve on each of the 3 loops (on the returns?)


    PS - there will be a Danfoss AVDO differential pressure bypass between the supply and return manifolds on the secondary.
  • Paul_6
    Paul_6 Member Posts: 88
    run,don't walk

    away from the plug type. if their the ones I'm familiar with they are very similar to a wedge type gas cock in that in about two years you won't be able to turn them. I had them on a job we rehabed and they ranged in size from 3/4 to 4 inch. you couldn't turn the big ones with a 4' wrench and most of the small ones snapped off, oh, and they don't have blow-out proof stems either. I like b&g for ball valve style and armstrong for globe valve style, if they are for equipment balancing put them on the return, for pump duty go with triple duty valves.

  • Paul_6
    Paul_6 Member Posts: 88
    b& g ball valve

    style would work well here, but you want to look at your flow rates, cv ratings. on the outlet of the 005 you would be better off with a smaller cbv full open than with a larger cbv throtled down.( may cause velocity noise). same with the manifold returns, size by flow/cv rather than pipe size.

  • ball valves?

    I thought ball valves were low on the list for types of valves to use for balancing.

    cbv = c_____ ball valve?


  • Paul_6
    Paul_6 Member Posts: 88
    cbv=circuit balance valve

    and they are not really ball valves. b&g makes one that is called a circuit setter, it has differential pressure ports, a scale to match pressure drop to a curve, and a memory stop feature so you could close it but reopen it without losing the setting. If you looked in the end of it without pipe, the port would look very much like a regular ball valve. I have a set of probes to read across the valve but don't have a diferential meter. most of the time i just take readings with a good quality gauge and use a little math to convert to feet of head. this works very well for most of the work I do, and if I find I need more accuracy I have a friend who is a balancing contractor. hope this sheds some more light on this, Paul.
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