GFIC tripping again

I have some more information on what causes unusual tripping of my GFCI. I have not had time to track it down because of other things to do. But, if anyone REALLY understands what is happening, I will be interested in knowing more.

I have been getting trips in my hobby greenhouse. I was using a switched surge protector as a convenient way for on/off switching of a pump for moving nutrient solution. To my surprise, the tripping takes place when the pump is turned OFF.

I know that turning off a pump can provide an inductive spike if it gets turned off when current is flowing in a winding. The transient, however, cannot be fed back through the hot conductor that is already opened already. I think that conduction through the neutral and ground wires is required. But how can that happen?

The surge protector has filtering capacitance and varistors. Inductive kicks can cause current to flow through them that otherwise would not be able to trip GFIC. Capacitors also provide ground currents that may not cancelled by opposite flow inside the current transformer used to detect faults. I know that a 0.25µF from hot to ground will trip a GFIC. This operation is also complicated by circuitry designed to detect neutral to ground faults.

I do have a switched power strip that contains no varistors or capacitors. When I get a chance, I will find if I can obtain GFIC trips using turning pumps with that. Meanwhile, there is an opportunity for someone to check out and explain just what the tripping details are.

Bill

Reply to
Repeating Rifle
Loading thread data ...

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.