NPSH Demystified: What Is It and Why Is IT So Critical?

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NPSH.  We know what it stands for—Net Positive Suction Head--but do we really know what it means?  Or why it’s so important?  More often than not, explanations of NPSH begin with confusing terminology and (even worse) confusing equations.  That’s not a good starting point.  The concept of NPSH is.
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“What Pressure Do I Pre-charge My Hydropneumatic Tank To?”

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 In our last blog we talked about how to properly size a hydropneumatic tank – but the engineer’s work doesn’t end there.  He or she also needs to specify the appropriate pre-charge on the drawings.  Otherwise the tank will not be set properly at start-up and will not provide the intended energy savings.
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How To Size A Hydropneumatic Tank in A Pressure Booster System

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 Properly sized hydropneumatic tanks are a non-negotiable element in a domestic water pressure booster system--including variable speed systems.  Without a hydropneumatic tank, pumps will short cycle on and off during no flow periods.  Even a leaky faucet can cause pumps to operate unnecessarily without this pressurized reserve of water.    
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ASME Hydropneumatic Tanks Play An Important Role in Pressure Booster Systems

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 “Do I really need a hydro-pneumatic tank on my variable speed pressure booster?”

 It’s a question many engineers will ask, particularly after ASHRAE 90.1 – 2010 takes effect in commercial building codes as early as October of this year.  As we discussed in an earlier blog on variable speed pressure boosting, the new ASHRAE standard no longer permits pressure reducing devices to reduce the pressure of water supplied by booster system pumps.  This essentially puts an end to constant speed pressure boosting, which brings variable speed to the forefront.  But since the whole point of variable speed pumping is to more accurately align demand with supply, why would hydro-pneumatic tank still be required?

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Flow Balance Valve Location: Supply or Return Side of the Coil

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Most agree (including those of us at JMP) that flow balancing valves should be placed on the return side of coils whenever possible. Why? Because this location helps reduce air and noise problems within the system.

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