8 hrs is a bit much unless you are trying to heat the pool. Most pools can get by with 2-4 hours of run time. Really just depends on how much skimming is required.
Normally a pressure switch is only adjusted if the heater is below water level. This is because it might stay on even if the pump is off. However, if you want to have a lower RPM while it is operating, you can adjust the pressure switch counter-clockwise. But I would first find out if the skimmers will work properly at lower RPM (they should). Water should flow over the top of the weir door when running the pump. Once you know the minimum RPM for the skimmers, you can then adjust the pressure switch so the heater works at that RPM.
Awesome that’s really helpful I appreciate it. I am trying to heat it but in the summer I will slow it way down. I didn’t realize that and have been running it longer. If you don’t mind I’ll check back with you if I have any more questions.