I have some odd behavior that I can't explain, so I thought I would post here looking for an explanation.
I recently replaced the A.O. Smith 1.5 HP 2 speed motor on my Hayward Superpump with the variable speed Ecotech EVSJ3-NS. The two speed motor was getting really loud and the low speed setting was not getting enough flow through my piping for the SWG to work properly.
When I replaced the motor, I found the impeller had a bit of pine needle crud clogging it in a few places, so I cleaned it out. (That may have been contributing to the low flow on the old motor on low). The new motor is now working great- I can set it at 55% to keep the SWG happy and bump it up to 75% when the Polaris is running. What is confusing me is the pressure readings. With the old 1.5HP pump on high and a freshly backwashed filter I would get about 16 PSI on my gauge. With the new 3HP pump at 100% the pressure on the gauge is only at 12 PSI. How can the pressure be lower with the new pump when it should be turning the impeller as fast as the old pump? Could the crud in the impeller with the old pump have impacted laminar flow and resulted in a higher pressure? Could air have been collecting in the filter with the reduced flow of the old pump/cruddy impeller and increasing the pressure reading?