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Formula for GPM
zepfan
Member Posts: 375
Is there a formula to determine pump gpm, when the pump curve is not available? Something other then a stopwatch, and a bucket? We have a extremely old pump that the manufacturer is un known. No nameplate
Thanks to all.
Thanks to all.
0
Comments


This is a good idea in any event. There is no saying it was sized correctly to begin with.ratio said:You can make a guess by looking at the pipe size, connected load, ΔT, etc., but aside from a true measurement, I think you're outta luck.
Post a pic, someone may recognize it.
"If you can't explain it simply, you don't understand it well enough"
Albert Einstein1 


Thanks to all. I was using the delta td x 500. And will try and get a picture0

Do it right. Figure out the connected load, BTU's required. Once this is known you can calculate the required flow. Once you have the correct flow you will need to figure out the friction loss through the piping and heat emitters, plenty of rules of thumb and charts to help with this. Once you have the required flow and a good idea of the friction loss it is easy to select the correct circulator.0

If you get to the point where you are looking for a decent SWAG and the load is unknown, plug in the GPM for the pipe size at 4ft/sec and use a delta T of 20. For example 1" copper carries 10.9 GPM at 4 ft/sec. 10.9 (gpm) x 500 (constant) x 20 (delta) =100,900 btu/hr. I have found that the majority of engineers design this way. In some cases, you can check a known part of the original design to verify the original engineer's preference and then apply the formula to the unknown portion.
http://s3.supplyhouse.com/product_category_files/11448FlowRateChart.pdf"If you can't explain it simply, you don't understand it well enough"
Albert Einstein1 

Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream1
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