How are you measuring water flow.

stefan66 Posted By stefan66, Jan 16, 2017 at 11:54 PM

  1. stefan66

    stefan66
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    The title says it all.
    Too much flow is unnecessary and counter productive especially flowing through the boiler. I see some cheap solutions online but I hate doing things three times.
     
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  2. jebatty

    jebatty
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    I measure flow by calculating the pump head round trip through which the water is being circulated and then applying that pump head number to the pump curve graph for the circulator to determine the gpm flow rate. Another method is to measure the pressure differential between the suction and discharge sides of the circulator, then convert the psi to pump head (1 psi = 2.3' pump head), and then use the pump curve to determine flow rate. Some circulators have fittings on the suction and discharge sides that provide access to determine the pressure differential using a pressure gauge. There are other more expensive or complicated methods.
     
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  3. maple1

    maple1
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    Never actually did.

    Trial & error for me, and much easier to measure temps.

    If dT is too big, flow is too small. If dT is too small, flow is too big. So I adjust pump speed & throttle a couple things. Also did some napkin type figuring of the kind mentioned above - pretty non-pro rough stuff going on at my place. :)
     
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  4. huffdawg

    huffdawg
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  5. peakbagger

    peakbagger
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    I agree that delta T is far more important than the actual flow. This Taco unit may be ticket and affordable http://www.blueridgecompany.com/radiant/hydronic/693/taco-variable-speed-delta-t-00-circulators, set the delta T across the boiler and it does all the work. Of course I don't know the details of your system so make sure the flow range and head is a good fit.

    I think this might be best used with a hydraulic separator. Not so sure how to integrate it with a thermovar boiler return temperature valve. I would probably dispense with the thermovar and just put a low limit setpoint on any of the zone pumps that would go through the separator until the return water goes over low setpoint.
     
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  6. stefan66

    stefan66
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    Thanks for the replies.
    Not sure if I really need one now.
    I usually can maintain 20deg. temp rise through the boiler.
     
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  7. BoiledOver

    BoiledOver
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    I measure the pressure differential of the circulator inlet and outlet, figure the math for "pump head" and compare to the manufacturers stated flow chart. Getting the differential is achieved by reading a pressure gauge that is mounted between two isolation valves, that is in a sidetrack (or bypass) of the circulator. Open one valve and close the other, record reading, reverse both valves, record reading and cypher the difference.
     
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  8. peakbagger

    peakbagger
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    Good idea, using the same gage to take both readings as it cut out a lot of potential uncertainty on the calculation. A differential pressure gauge is better and a DP transmitter is probably the best. Every so often I run into orifice plate installs with a DP pressure gage plumbed to it with a custom gauge face that shows flow. Pretty good except no temperature compensation.
     
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  9. Iconprocontrols

    Iconprocontrols
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    You can use a paddle wheel flow meter to know the exact amount of water flowing through the boiler. These paddle wheel flowmeters produce perfect results, they might be a bit costly but their result is fantastic.
     
  10. Bob Rohr

    Bob Rohr
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    I put one of those plastic meters on a demo display I built. The dealer told me it was rated for 170F. The screen got fogged up first time, running 160° , the electronic circuit board got wet from the condensation, now it doesn't read out?

    I think a brass circuit setter or quick setter is better suited for hydronics that run in excess of 180F often.

    I've also used the Blue-White brand flowmeters on solar for decades, they work and last at those high solar temperatures.
     

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  11. nhtreehouse

    nhtreehouse
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    Hey Bob, any chance you know of a reasonable flowmeter transducer with some electrical output, either frequency, 0-10V/2-10V, or 0-20mA/4-20mA? I thought I saw Caleffi had some sort of solar meter with some form of transducer. If I had such a device I could very easily BTU meter my house, figure out where losses are and so on. Thinking much lower flow rates than the boiler application - likely under 2GPM, certainly under 5GPM.
     
  12. Karl_northwind

    Karl_northwind
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    I have one of the caleffi electronic flow meters, never wired it up. seemed like a good idea at the time. I do use the caleffi visual flow meters in several of my systems (2 here at home) I use a 132 quicksetter PN132662A in my big system, and a NA223529 flowmeter in my small system. they both have handled 200F fluid temps no problem.
     
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  13. Karl_northwind

    Karl_northwind
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    That said, when I do the math using the Taco TD-10 circulator sizing worksheet, it tells me what the flow rate is/should be and when I've been able to check it's been spot on with the pump curve.
     
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