I wired the new pressure switch just like the old one in this pic. But I hate doing things I do not understand (I followed the old setup because I know the company that did it and trust their work). Could someone please help me understand why 4 wires are not used? This is the 5 hp pump I worked on earlier this month. I read somewhere that 2 wires can be used on 3 hp and higher pumps, but once again, I do not understand the difference in the wiring setup. Why would smaller hp use 4 wires? Thanks for any input.