I installed a new motor due to the bearings going out on my old one. I have previously replaced the bearings on the old motor a couple of times before but this time it got real hot and melted the plastic fan and it would no longer fit on the shaft to spin and cool the motor. Long story short I neglected to do the proper research and purchased a smaller motor. The old motor was single speed 240V 1.5 HP / 1.5 SF (SFHP 2.25) and the new one is single speed 240V 1.5 HP / 1.1 SF (SFHP 1.65). It runs fine with normal pressure for a while but then the thermal protection kicks in and shuts if off. I now know (or think I know) I should get a smaller impeller to match my now smaller motor. I have a 1.5 HP pac fab challenger pump. Anybody familiar with these pumps know what impeller size I should be running with this new smaller motor?