rpackard
Senior Member
- Joined
- Apr 16, 2012
- Messages
- 127
- Location
- usa
- Vessel Name
- formerly owned Puffin/Lilliana
- Vessel Make
- Willard 30/40
I have used both ultra switches and water witch switches. The ultra switches will stop working if you get bilge grud inside that blocks the float. It is easy to disassemble and clean out. The water witch switches will not work properly unless the two electrodes are kept clean. YMMV.
It is the inductance of the pump motor that causes the voltage spike across the switch terminals when the pump is turned off. If you remember your high school science the voltage is L di/dt where L is the inductance and di/dt is the rate of change of current. When a mechanical switch opens the rate of change of current is huge. That is how the old ignition systems with “points” developed over 10kV across the spark plug.
It is the inductance of the pump motor that causes the voltage spike across the switch terminals when the pump is turned off. If you remember your high school science the voltage is L di/dt where L is the inductance and di/dt is the rate of change of current. When a mechanical switch opens the rate of change of current is huge. That is how the old ignition systems with “points” developed over 10kV across the spark plug.