Most people just use a little pressure relief valve that can dump to a drain for high-pressure protection. I would want a pressure relief valve as a back up for a high-pressure kill switch anyway. Your system would never go to a high-pressure condition if a switch were 100% dependable way of shutting off the pump in the first place. So you are counting on another switch to catch the failure of the first pressure switch. When one switch has failed because the connecting tube is clogged, the tube that connects the high-pressure kill switch will probably also be clogged. If a magnetic starter is stuck closed, opening two switches instead of just one is not going to un-stick it.
I believe a pressure relief valve is preferable to a high-pressure kill switch. It is completely mechanical and totally independent of the switch, starter, and other controls for the pump.
That being said, a high-pressure kill switch can certainly be used if you want. Check with the manufacturers of Pivot Irrigation Systems. They use a high-pressure kill switch on their big circular sprinkler systems. It has a manual reset button, which is imperative for a high-pressure safety switch. I am just not sure how high the pressure setting can go on these type switches.
Using another regular pressure switch as a high-pressure kill doesn’t work. When the pump shuts off on extreme high-pressure, you don’t want it starting up again at low pressure. A regular pressure switch will restart the pump and the system will just continue to go to the extreme higher-pressure switch over and over instead of shutting down as a fault.
