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Measuring pressure differential to calculate flow

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mattmia2
mattmia2 Member Posts: 9,747
What is an inexpensive way to measure the differential pressure in this type of balancing valve to calculate the flow:
https://www.supplyhouse.com/Macon-Balancing-MB-STV-NPT-3-4-3-4-NPT-STV-Balancing-Valve

Is this kind of pressure gauge accurate enough or is there a better way?:
https://www.pce-instruments.com/us/measuring-instruments/test-meters/differential-pressure-meter-pce-instruments-differential-pressure-meter-pce-p30-det_2151335.htm?_list=kat&_listpos=7

Is there an inexpensive source for the needles to connect to the rubber glands?

Comments

  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    edited November 2019
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    That's a manometer and it is not for measuring water pressure differential.
    The valve has 2 ports for standard pressure gauges, but it looks a little delicate to me.

    There was an error rendering this rich post.

  • mattmia2
    mattmia2 Member Posts: 9,747
    edited November 2019
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    The knob on the valve looks comically large but it actually feels pretty solidly built. there is a stop you can set inside the stem that will allow you to close it and open it to a preset point, they actually seemed more sturdy than i was expecting.

    What would be the gauge to use? It appears that something on the order of a couple tenths of a psi is what you need to measure looking at the chart with the valve.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,624
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    @mattmia2
    I would call the mfg and ask them if it will do water pressure. I beleive it will.

    It's rated in psi and feet of water and they have models that go to 30 psi and even 100psi. I couldn't see in the manual about what fluids you can measure ....unless I missed it.

    that's a good price if it will read water......ask about glycol
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,624
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    @mattmia2

    You can get needles at a supplier that sells pneumatic tubing and pneumatic controls there used to test pneumatic thermostats etc
  • mattmia2
    mattmia2 Member Posts: 9,747
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    @mattmia2

    You can get needles at a supplier that sells pneumatic tubing and pneumatic controls there used to test pneumatic thermostats etc

    thanks. so it is just a 23 gauge hypodermic needle? i think i can find a needle and adapters.

    I e-mailed asking if that was for liquids or gas only and they said one of the models was for liquid but they said that the specifications and instructions said that, but i couldn't find anything about liquid of gas in the instructions, the response said something about less pressure in liquids. I think they might have not understood that In. H2O was just a different unit of pressure.

    Dwyer makes some relatively inexpensive 0-5 psi differential pressure gauges which are definitely rated for liquids which i am also looking at.
  • ratio
    ratio Member Posts: 3,653
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    Are they Pete's Ports? Not sure I'd stick just any old needle into one.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,624
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    I have used almost any pneumatic needle with no issues.

    bell & gossett make a differential pressure meter
  • ratio
    ratio Member Posts: 3,653
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    Ah, a pneumatic needle makes sense; that's not what came to mind when I read 'hypodermic needle'.

    I use a few different off-the-shelf gauges (depending on the required scale) & a handful of brass adapters. I've considered getting a differential pressure module for my Fluke 717, but I really don't need it that often or that accurate.

  • Zman
    Zman Member Posts: 7,573
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    I've only used and seen the hydronic manometers. Worked for a company that had an old B&G that I liked. I have a buddy who has a Dwyers that I use from time to time.https://www.testequipmentdepot.com/dwyer/accessories/kits/hydronic-meter-kit-490a-hkit.htm

    It would nice to know of a less expensive option. Let us know how this works out.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • mattmia2
    mattmia2 Member Posts: 9,747
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    Looking at the Johnson Controls needle, it is just a 23 gauge medical hypodermic needle, tubing adapter, and a huge mark up.
  • Zman
    Zman Member Posts: 7,573
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    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Zman
    Zman Member Posts: 7,573
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    I am sure you could use something else. You will get wet if you do.
    This is why I like the Calleffi quick setter so much. It costs a little more but no special tools needed.https://www.supplyhouse.com/Caleffi-132552A-3-4-NPT-QuickSetter-Balancing-Valve-w-Flow-Meter?gclid=CjwKCAiA8ejuBRAaEiwAn-iJ3lzlEqEsvrOKxNMlnDU5zZRkFaXQcYxZcVwJY12X2PyHVxASBRNGshoCAmUQAvD_BwE
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • mattmia2
    mattmia2 Member Posts: 9,747
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    I thought about using one quicksetter flow meter somewhere where it saw the full flow of the pump and using it to set one zone at a time one that could handle the full slow of they system with all zones calling wasn't precise enough for a single zone. i guess maybe in the grand scheme the extra cost wouldn't have been a big deal although the macon valves provide a balancing valve and shutoff all in one, there is a stop inside the stem that you set once you find the setting that only allows you to open it to that setting again and being a 10 turn device that setting should be pretty repeatable. A ball valve with a stop is a lot less precise.
  • mattmia2
    mattmia2 Member Posts: 9,747
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    This is the Johnson Controls probe for their pneumatic systems, the blue fitting means it is 23 gauge. It is clearly just a medical hypodermic needle.
    https://www.supplyhouse.com/Johnson-Controls-JC-5361-Hypodermic-Needle-Test-Probe-Assembly
  • ratio
    ratio Member Posts: 3,653
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    I read over one of the brochures: it still looks to me like a Pete's Port. They use a dull, rounded needle to enter the gland, not a sharp needle. I'd hate to see them all leaking because the wrong needle style was used. Then again, I don't do this very often, take what I say with a grain of salt.

    Maybe a call to the mfgr &| supplier & ask it if's compatible with Pete's Plugs? IIRC they're cheaper than the Johnson needle…