What is "normal flow rate" and

John B_2

how do I measure it?

Brad White

Wide range of Normal

A traditional temperature drop for a hot water system is 20 degrees. I have designed systems for 30, 40, even 60 degrees and larger temperature drops. But 20 is a default and I would say 80 percent of systems use that as a design standard.



Short of having good temperature instruments, the best bet for most design work is to calculate it.



That said, if you know your BTU per Hour output, divide that by 10,000 to get gpm or gallons per minute.



The 10,000 figure comes from 8.33 (lbs. per gallon), x 60 minutes per hour (to get you to "pounds of water per hour", x the temperature change.  As you know, a BTU is the amount of heat to change the temperature in a pound of water by one degree F. So this should make sense.



A boiler with a gross output of 200,000 BTUH would have a flow rate of 20 gpm by this example. 100,000 BTUH, 10 gpm, etc.