installed a hose engineheater on a car, and to get the warm water around the engine i wanted a waterpump to start automaticly (one i took from an old w202 gasser)
the 220v relay is activated when the plug is connected to the car with 220v, that activates the pump and the ressistor in series with that, if the pump should brake and have an open circuit it wont be any voltage over the resistor (R1) and thus the 4v relay that is activated over the resistor wont close, that means the 12v relay wont get a closed circuit and the engineheaterelement wont burn itself to death.
the Therrmostat is a Normaly-closed one, that opens when over 70degree, that is on the heater element, and incase the pump would brake, and instead of open circuit, be a closed one, the Thermostat will stopp the power to the engineheater before it overheats.
please ask if you wonder anything about this setup,