Electric motor with long distance control wires

Discussion in 'The Projects Forum' started by Escape Artist, Feb 17, 2013.

  1. Escape Artist

    Thread Starter New Member

    Feb 17, 2013
    I have a water pump that fills a tank that is about 1000 feet away. The tank has an electric float switch with 20 awg wires running back to the pump house. The pump is 240v. I have a contactor that is 240v as well. However, I don't want to run 240v in the control wires all the way to the tank for two reasons. One is it seems rather dangerous. The second is that is a long way and I may get some current in an open connection from cable capacitance.

    So, my plan is to use a switching power supply to go from 240vac to 24vdc which will power the control loop. Then, I will have a SSR relay that switches on/off the coil of the contactor. Finally, the contactor will turn on and off the motor.

    This seems way over what I should need, but I can't seem to think of a simpler solution. Any ideas?
  2. #12


    Nov 30, 2010
    Use a float switch that stops the water flow. Put an air tank next to the motor. Use a pressure switch to stop the motor. Presto. No electrical control circuit at all.
  3. crutschow


    Mar 14, 2008
    Buy two identical 240Vac to 12Vac or 24Vac transfomers. Connect one transformer 240V winding to the mains 240Vac. Run the 12/24V output to the float switch. Connect the float switch output in series with the 12/24V winding of the second transformer. Connect the 240V winding of the second transformer to the 240V relay coil. The transformers only need to provide the power that the relay requires so they can be small.

    With that configuration you will only have low, isolated voltage going to the float switch.