Zone Flow Velocity and GPM Calculator (Spreadsheet)

5 minutes of effort. Spreadsheet is attached. User input is the yellow background cells.

User Enters:
1) Individual zones length in feet.
2) Time in seconds from circulator start to first sign of hot water at the far end of the zones return leg (I.E., feel for return leg getting warm)
3) Zones pipe ID

Spreadsheet kicks out:
1) Zones flow velocity (in FPS)
2) Zones flow rate (in GPM)

As always, kick the tires and let me know if it works.

OK, I finally timed my living room zone with my circulator set for its low speed, and while holding the return leg pipe and feeling for heat I timed 68 seconds from circulator start and zone valve open to first warmth at the tail end of the return leg (where the 3/4" pipe enters the 1-1/4" return manifold). Allowing for 2 seconds for my brain to register that my hand was feeling a bit of warmth, and then for me to respond by clicking the button on the timer and stopping it, I'm calling it 66 seconds.

My best guesstimate of the overall length of 3/4 copper pipe for my Zone 1 is 126 ft. 3/4" copper has an ID of 0.811".

Using the spreadsheet I attached in this forum thread I come up with 3.078 GPM. I'm calling it 3.1 GPM. This result is with my DPBV active. Therefore my previous guess of 2.55 GPM with the DPBV active (as seen in a different forum thread) has proven to be incorrect.

When I plot a 3.1 GPM point on my system curve for the circulator at low speed for only 1 zone open, and then extend a line from there to the intersection of the system curve and the circulator curve for 4 zones open (which is the point at which the DPBV closes fully), I amazingly find that the DPBV has completely flattened out the curve of the circulator, and thus it is acting just as if I had installed a variable speed circulator that was set to a constant pressure setting. The result is a horizontal line. It looks like the lines drawn for DPBV's in the textbooks. I'm pleased.