old pump new motor - figuring out the specs

[mas985]

The return head calculated by filter pressure includes both dynamic head and static head. So does the suction measurement. The numbers in the table include only dynamic head so if you are trying to reconcile the numbers, you need to take this into account as well. If the pump is elevated above the pool level, this can account for some of the differences.

Also, I have head loss numbers for some equipment but not all equipment. For example, Hayward publishes the head loss numbers for their filters but not their multi-port valves. However, Pentair publishes head loss for their multi-port valves so I use those numbers instead and they may not be an exact match so there could be some error for that.

Also, please keep in mind that these are all estimates and the error can be quite high because of the limits in measurement accuracy including: pressure and suction gauges, equipment manufacture measurements and the CEC pump measurements. All have uncertainty and it is impossible to eliminate all of the error. I do the best I can with the information I have.


The plumbing curve defines the dynamic head loss in the plumbing vs flow rate by this equation:

Dynamic Head Loss (ft) = Plumbing Curve * GPM^2

The operating point is where this curve crosses the pump head curve. So you can plot this curve over any pump curve and find the new operating point.

 

[Diver]

Thank you Mark. With the head loss numbers that I have, would I benefit more from adding another 1.5" pipe to suction or return side of the plumbing? I have a dead return that I want to restore at some point and add back into the system.

It seems that return would benefit more since the loss is greater there.

 

[mas985]

Probably not. Most of your head loss now is in the filter and valve and an extra line won't help that.

 

[Diver]

interesting. thank for your help!