What texie was really getting at was that load, on a centrifugal pump, is equal to flow. Flow is a factor of Total Dynamic Head (TDH) and fluid velocity. So if you have not changed the speed of the pump, the velocity would be the same, therefore you (or someone else) have done something to change the TDH. TDH consists of the static head pressure, which is based on elevation change and is not likely to have changed either, friction, meaning the number of bends and pipe diameter changes, and any restrictive elements, such as valves. So in all likelihood, the thing that is most probable to have affected the motor loading is that there is a valve somewhere that is not set correctly for the design of the system. Was it working fine for a while and then started tripping?
Damn, I have to remember to read BOTH pages before responding, because as per usual, GoldDigger beat me to it...
And in fact one-upped me on the blown-out filter medium possibility, hadn't though of that.