Perhaps this is a naive question, but I always assumed the benefit of a VS pump was that one could more precisely regulate the flow rates to achieve optimum efficiency. I figured that if my old 1.5 hp SS super pump II consumed 1500 watts to move 40 gal/min that a VS pump would also use the same wattage to move the same amount of water. I am finding instead that i can move 40 gal/min with my 3 hp Intelliflo with only ~250 watts. I can move 75 gal/min before the reading reaches 1500 watts. To be sure, I've made other changes to the equipment pad: new cartridge filter (but roughly the same sq ft as before) and a new heat pump (in lieu of a propane heater).
The other big change was that my pressure gauge on the old system would read ~18 psi for 40 gal/min whereas my new system is reading about 3-4 psi. If I crank the pump up to 70-75 gal/min, I can reach ~13 psi.
Currently, I'm trying to heat our pool with the heat pump and am running continuously at 1500 rpm which yields a flow of ~30 gal/min; psi = 1-2; and watts = ~185.
My hypotheses are:
1. improved hydrodynamic efficiency of the pump?
2. freer flowing filter (although the pool service previously taking care of this stuff assured me the filter was clean and the PSI of 18 was normal. I inherited the pool late in the season and sold the old filter without checking).
3. improved plumbing efficiency. With replumbing, I was able to reduce the number of 90° elbows in the main circulation loop and incorporate mostly sweep elbows (but Mas has repeatedly debunked the value of this modification).
Don't misunderstand: I'm not complaining! I'm simply flabbergasted at what appears to be a violation of the laws of physics. If this continues, my ROI for the new pump will be one season with the electrical savings.