<a href=showthread.php?s=&postid=14077904#post14077904 target=_blank>Originally posted</a> by capn_hylinur
Paul----how do fish take care of themselves when it comes to stray current?
<a href=showthread.php?s=&postid=14078838#post14078838 target=_blank>Originally posted</a> by Michael
i think under fault conditions when a heater shorts out or a pump connection gets exposed to water, or the lights fall into the tank etc a probe is useful as the fault current from the faulty appliance will go to ground down the probe and trip the gfci, if the probe wasnt there then you would be the path to ground when you put your hand in the tank, even though the gfci would trip youd get a nasty shock, providing of course the fault current exceeded the rating of the gfci, usually in north america its 5ma, admittedly its possible that any live stock could be injured or even killed under such circumstances, but rather them than me or the kids, its a difficult subject really to discuss properly because both arguments have merit, but water and electricity just dont mix so any connection to ground which would blow a gfci before you could potentially get a shock has got to be considered worthwhile, obviously a gfci would work without the probe by any inbalance between cores, and providing the house electrical system was in good working order and inspected regually there would be more chance of it working properly if tested regually and it wasnt a faulty unit, but poor electrical connections and bad continuity between ground connections then potentially theres danger, i mean how many of us know how safe our electrical installation systems are? i think if a probe is in place and has a confirmed continuity connection to a ground point and the gfci has been tested and confirmed as in working condition then as far as safety is concerned it got to be a good idea, however i can understand fish lovers dont want fault current killing their beloved livestock, i think theres a fine line between stray voltage or inductance which is relitively harmless and expected with electrical appliance under water and a fault current which can potentially kill, we dont know when we put our hands in the tank which is going to be there, unless we test with a meter every time we go near the tank, i think wed all agree this is impracticable, fault current doesnt smell, you cant see it or i doubt youd hear it either, so having the probe which will allow it to travel to ground and trip the circuit must be a good idea, the downside is that the tank electrical system, could by being dead, crash the system, hense the multiple gfci, if each appliance or 2-3 at most were on seperate units then only the fauly unit and maybe 1 or 2 other appliances would trip, this way something still stays on and the tank is ok, perhaps a good idea to to spread powerheads about on different gfci s and at least the live rock is still working, a bit long winded and no doubt still wrong in some eyes but i felt i had to say a bit more, i feel myself that this is a pretty good argument, im not going get into a heated debate but the thread seems to be going around a bit in circles now, so i thought id back 1 or 2 other views which have already been posted
<a href=showthread.php?s=&postid=14080391#post14080391 target=_blank>Originally posted</a> by cczarnik
Ya'll are still at it. I'm going to try to bring some data to this thread. It's long, but hopefully worth it..
Here's my standard mythbusters / jackass disclaimer... My work below involves intentionally energizing water with 120VAC. Don't try this at home
As I wrote before, I'm one of the few unfortunate that completely nuked a tank from a failed heater. There has been speculation in this thread (and elsewhere) that it wasn't electrocution, but probably pollution from the plating effect of submerged, live conductors that killed the stock. So tonight I got out my meter, a bucket of SW and a loose 120v cord and decided to replicate the conditions.
I stuck the cord into the tank, plugged it in. Nice buzzing sound, some little sparks, lots of electrolysis from the terminals, and little clouds of debris coming from terminals under the water. However at any two points, I could not get an AC voltage read of more than about .1VAC. This suggests to me that the energy in the tank was largely confined to the a path between the two terminals. I then spread the terminals out to 6+ inches. No difference. Preliminary conclusion: exposed equipment wiring will probably NOT electrocute the tank. Taken with my heater failure on a live tank and observations here, I will however claim that the pollution from energized copper terminals is substantial, and reached lethal levels in just a few hours (in my 24g tank).
Amperage draw from this scenario is not enough to trip a breaker (I'd only estimate an amp max, but my clamp meter was at work). I was surprised to see this result- I really thought there would be potential across different areas of the water. I suspect it was there, but was so noisy my meter couldn't detect (I saw a cool voltage mapping tool in my datacenter days that I really wish I had right now)...
This entire trial was run on a GFI protected circuit. As speculated in the thread, the GFI did NOT trip, because the current path flowed exclusively between the conductors submerged in the water.
I ran another trial with a ground inserted, approximately 10" from the exposed terminals. The GFI instantly tripped (and I mean instant, just like pushing the test button). This is the exact solution I am looking for in my tanks - GP + GFI interrupts the current flow upon fault of an electrical device. It took them both, and it was nice to empirically verify what I was trying to accomplish.
The next test will be to look at ground probe effectiveness as a function of distance to the fault. It's going to take more than a bucket of water for this- I'll have to wait to the next water change and I'll rig up something to test effectiveness equivalent to a sump (to help inform the multiple ground probe questions and speculation from this thread). I got some thoughts using a garden hose to simulate remote tanks.
I did not test ground probe / no GFI, as the GFI was there for my safety. But it would obviously introduce another current path, and nothing would be there to kill the circuit. From trial #1, this is obviously not good for the inhabitants (or the hobbyist).
Hope this helps, Chuck