Most motors have an overload built into them. But overloads are only made to protect the power company, not the motor. By the time an overload trips the motor and/or pump is probably already dead, as it will have been running dry or cycling on/off rapidly for quite a while.
The Cycle Sensor detects rapid cycling and dry run and shuts the pump off almost immediately. You can just reset the Cycle Sensor and the pump will start up again. Then you will need to figure out why the pump is cycling or running dry, as the Cycle Sensor will just turn it off again, but at least the pump will not be destroyed.
Having a Cycle Stop Valve on the pump greatly eliminates the chance of cycling the pump to death, so that feature of the Cycle Sensor hopefully won’t be needed.
The Dry run feature of the Cycle Sensor is really only needed if the incoming water source to the pump is not reliable.
A pressure relief valve will only be needed if there is a malfunction that keeps the pump from shutting off, as it should.
The pump, Cycle Stop Valve, pressure tank, and pressure switch will work fine without any additional safety devices. And the Cycle Stop Valve eliminates most of the possible failure mechanisms in a pump system.
However, safety devices like the Cycle Sensor and a pressure relief valve can be good as additional insurance. The cost of the pump and the amount of inconvenience for being out of water until the pump is replaced, are the best ways to judge if you need safety devices or not. Is it better to have it and not need it, or need it and not have it?
