trying to determine flow rate

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  #41  
Old 12-31-11, 04:59 PM
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i got it now. you solve for flow at different head values to make the curve for the pump.
Great, man! You now now know more than many of us here, and at least as much as me.

When you say, "make the curve of the pump," I would say "intersect the curve of the pump."
 
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  #42  
Old 12-31-11, 05:35 PM
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Yeah, the curve for the pump is already made, you will make the curve for the SYSTEM.

It won't be far from the one I already posted. The huge majority of the head in that loop is from the PEX tubing... the other stuff you will find will shift the curve to the left a little bit. But I can tell you right off the bat that the 15-58 you will find to be 'man enough' for the job. (although, when you solve for glycol, you will find it shifts a LOT to the left... )

By the way, that article by Siggy doesn't have the 'numbers' for glycol in it... you may be able to get close with the numbers from the Taco pub. (that's the DENSITY and VISCOSITY terms in the equations) Or, you may be able to get those numbers from the data sheet for the anti-freeze.
 
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Old 12-31-11, 06:01 PM
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i need to get my terms right but your diagram helped me tremendously. i am referring to the system curve that you plotted for me and overlaid it onto the 15 58 pump curve. ( i think those are the correct terms) this was a great exercise for me, and i was doing it totally wrong at the beginning of the post. thanks to all for your explanations, and patience.
 
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Old 12-31-11, 07:28 PM
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can you tell me where i can get ( hopefully free) software or symbols to diagram this system so i will be prepared the next question i have to ask?
Offhand I don't know of anything that's 'free'... I use a program called PaintShop Pro that's very similar to PhotoShop. For symbols, I go to manufacturer websites and download the manuals and cut and paste the symbols from them. I find that HTP products has pages of symbols in their I&O manuals.
 
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Old 01-07-12, 08:37 PM
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update

while researching something else, i came across this website which i had seen long ago, but of course, forgot about it.
Pump and Pipe Sizing for a Solar Water or Space Heating System

i know these posts are read long after the issue is resolved so i offer this info to anyone else who finds this post with a similar situation.
 
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Old 01-07-12, 10:46 PM
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Just want to point out for the record... the solar page that Montana linked to is discussing, until the very end, an OPEN SYSTEM. The last part discusses CLOSED systems.

The difference being that the vertical height of the building has NO BEARING whatsoever on pump selection in a CLOSED system. It does state this fact in the last section of that linked page, I just wanted to make it a bit clearer...
 
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Old 01-11-12, 09:29 PM
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sorry, i should have pointed that out. just an update. I was originally trying to figure out the flow rate to see if i could run both pumps at slow speed to increase the temp and slow the rate of the glycol through the heat exchanger. after staring at the pipes for a while, and after digesting all the info in this thread, i turned off one of the two pumps in the loop. Immediately, the temp went up by 10 degrees in the loop and the pool heats faster. the key was to slow down the flow. I had tried reducing both pumps to slow, but the temps in the loop went too high. But leaving the one pump at medium and turning off one pump did the trick.
 
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