Question
I also work for the parks,we have an old system with pressure switches 2 pumps one is backup,replaced pressure switches,filters,check valves,coming from a lake,pressure wont turn off pump even after 3 diffrent switches,we also are using expansion tanks,is there abetter way to convert all this over so we dont keep overheatin the pumps?

Answer
There has to be a reason why the pressure is not being sensed by the switch.  Check the line that feeds pressure to the switch for debris or obstruction.  Also make sure that your pressure tanks have no leaks, that they are properly pressureized (espescialy if you have one that has a bladder in it).  If it worked at one time, it should work again.