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  1. #1
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    Balance valves on return vs supply?

    I'm doing a take-off on a chilled beam and chilled water system where both systems share a common chilled return. I've already requested main branch balance valves on the heating hot water system and the general contractor asked me to review the chilled water piping. I don't see asking for main branch valves on the common returns. Does anyone have any reason why I shouldn't request that they install the balance valves on the supply sides so I can differentiate flow rates between the chilled beam and chilled water loops? I never see balancing valves installed on the supply side of systems and was wondering if there is a logical reason for this.

    Sorry if this post seems vague, I didn't want to get to wordy.

    Thanks in advance for your insight.

    Everyone stay safe.

  2. #2
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    on return side idea is to keep your coils full of water is what I understand?
    Keep it simple to keep it cool!

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  4. #3
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    Quote Originally Posted by stanbyyourword View Post
    on return side idea is to keep your coils full of water is what I understand?
    X-2

    Keep the coils flooded

  5. #4
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    In a closed system keeping the coils full of water isn't a problem. There is a thread that discusses balance valves versus control with equal percentage control valves that gets fairly detailed.
    No man can be both ignorant and free.
    Thomas Jefferson

  6. #5
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    Quote Originally Posted by balancer3414 View Post
    I'm doing a take-off on a chilled beam and chilled water system where both systems share a common chilled return. I've already requested main branch balance valves on the heating hot water system and the general contractor asked me to review the chilled water piping. I don't see asking for main branch valves on the common returns. Does anyone have any reason why I shouldn't request that they install the balance valves on the supply sides so I can differentiate flow rates between the chilled beam and chilled water loops? I never see balancing valves installed on the supply side of systems and was wondering if there is a logical reason for this.

    Sorry if this post seems vague, I didn't want to get to wordy.

    Thanks in advance for your insight.

    Everyone stay safe.
    Try This
    Attached Images Attached Images

  7. #6
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    Thread Starter
    Thanks for the input and manual that I will eventually get around to looking at. However, in my case, does anyone see an issue with installing them on the supply side as installing one on the common return will not tell me how much flow is chilled beam vs chilled water. I kind of understood why they install the CBV's on return side at the coil.

    Not to confuse the original question but here's another one that I don't understand:

    If both pumping system share a commons return and both the chilled water and chilled beam pump control to a differential pressure via VFD, wouldn't they fight one another as each different system pump ramps up and down?

  8. #7
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    You have 2 or more different GPM Requirements so you will need 2 or more balancing valves.

    As far as the pumps that will depend on the piping layout.

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  10. #8
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    Control of the pumps should be by differential pressure not GPM. The pumps will ramp up and down to maintain set point.
    No man can be both ignorant and free.
    Thomas Jefferson

  11. #9
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    Thread Starter
    Quote Originally Posted by WAYNE3298 View Post
    Control of the pumps should be by differential pressure not GPM. The pumps will ramp up and down to maintain set point.
    The pumps are modulating based on differential pressure and not flow. Both the chilled beam and chilled water share a common return. This is why i presented my initial question regarding installing the balance valves on the supply side of the main branches, it is to differentiate between flow on the chilled beam and chilled water system. If I had one installed on the common return, I wouldn't be able to do this. The second half of my question was regarding the controlability (is that a word?) of the systems independently with each system sharing a common return pressure for differential pressure control. I imaging that I would have to establish both of the differential pressure set points at the same time once the systems are balanced in a full open scenario (minus any diversity). Just seems to me that as one of the systems is modulating it would have an impact on the other. Maybe not.

    Thanks for everyone's input

  12. #10
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    They will impact each other but the pump VFD'S will modulate to maintain differential pressure set point. As long as both pumps are maintaining DP set point you will have design flow to each system. That's why DP is used instead of discharge and or return header pressure.
    Most closed systems have the balance valves on the supply but if you want them on the return no problem. I like your thought process though.
    No man can be both ignorant and free.
    Thomas Jefferson

  13. #11
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    id do discharge of any chiller or pump. its better to keep the impeller loaded then not on the pump.
    And by keeping pressure on the chiller reduces the possibility of any cavitation.

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