Stray Voltage + Ground Probe = Stray Current

Let us begin this discussion with a look at voltage:

Voltage represents a potential energy which in and of itself does not perform any work whether that work is good or harmful. Consider an analogy with gravity, which also represents a potential energy. Say you are on the second floor of a building ie at an elevated potential. Unless a path to a lower potential is available no work is done. Now let us say you find a hole in the floor which represents a path to a lower potential ie the first floor and a path for work to be peformed. Well we all know what will happen if you fall through that hole...

No let us apply this to voltage, which in and of itself is as harmless as being on the second floor of a building. Ever seen a bird sitting on a power line? Was the bird in obvious distress? Of course not. Unless a path is introduced to a lower voltage, no work is done, no harm no foul. Ever see a bird that attempted launch and contacted the ground wire and the elevated voltage wire thereby creating a path and allowing work to be done? Roasted pigeon anyone...

Now let us extrapolate these examples to the aquarium. If stray voltage is present in the aquarium without a path to ground your fish are like that bird on the wire, unharmed. However when a path to lower potential is introduced ie a ground probe you have now given the potential energy in your tank a conduit to do work which may or may not have deleterious effects on the inhabitants of your aquarium...

Finally let us discuss the possible sources of voltage in the aquarium:

First is the equipment itself. It is my understanding that a properly functioning UL listed for aquarium use piece of equipment will not introduce stray voltage into the water. Malfunctioning equipment can be a different story but with a properly connected and functioning GFCI power source this becomes a non-issue.

Second is the ionic content of salt water. It is plausible that charged ions in the water can cause an elevated electrical potential. In this case look to the bird on the power line example to see why we would not want a path for current and work to be done.

Third is current induced by rotating magnetic fields in pumps and the motion of the salt water itself. A changing magnetic field will always induce a current which creates an electrical potential. Again it seems the bird on the wire example applies here.

Other sources?

Please note that these are my personal observations based on my time in college acquiring a BS in Electrical Engineering and my current work as an electrician.

Your thoughts?

 

Any takers ...

 

Background: Communications Tech / Avionics Tech

I agree with most everything you say, except for one. The whole bird on the wire effect. This is mostly true. The problem is that you are an awesome ground. That potential voltage will be there ready to course through you as soon as you touch the tank. I have been shocked by a power head before. Not fun.

That being said. If you do have stray voltage, I would do everything possible to remove the source of the voltage leak.

 

This is the precise reasoning for using GFCI protected receptacles.

 

I use GFCI breakers. I do not trust most GFCI outlets.

 

Nice analogy. I use a ground probe to make my GFCI trip before I stick my arm in the tank and provide a return path.

Background: MS in electrical engineering.

 

I was just sitting here thinking that a ground probe would actually be a good supplement to GFCI protection in order to create a current path to trip...

Do you then keep the ground probe in your tank at all times or only when you are working in it?

 

This has been brought up alot in the past....http://www.3reef.com/forums/general-reef-topics/interesting-reasons-not-use-ground-probe-63779.html

 

Thanks for the link Robman.

 

No Prob...I personally dont use one..I stand on a wood chair..hahaha.