stray electrical current??????

[lark]

What negative effect does a ground probe when used with a GFCI have when used on a tank? [/B]

To summarize my too lengthy post on the matter, the proposition being asserted here appears to be that induced voltage and current in the tank will cause unacceptable currents in the tank for livestock if a grounding probe is used.

I am seriously skeptical of this claim.

It also seems pretty soundly refuted here, but I cannot understand some of this: http://www.reefs.org/library/aquarium_net/1298/1298_3.html

 

[Deleted member 143833]

A ground probe placed in a tank will complete the electrical circuit; it's like touching hot and ground at the same time except in the water the current flows between the faulty device the the ground probe. Without the probe there is no circuit.

An example would be to take a electrical cord and strip the ends so that you could see the bare wires. You can safely touch 1 wire DON'T EVER TOUCH BOTH AT THE SAME TIME. A very simple example but in principle it is very close.

Personally, I would never use a ground probe and I would always use GFI outlets. That is me however, I have seen people run tanks without GFIs and only a ground probe and I have seen tanks with nothing.

I've read Gerry's article and I don't believe that it refutes anything regarding the use of a ground probe but perhaps I don't understand why you felt that it does, it does confirms that there is induced electricity in our tanks, I don't think that was in question though.

And for the record I was a electrical beginner for about 20 years before I moved into software.

All said however, each person must be comfortable with what they do with their tanks and the precautions they take so if you feel better having a ground probe then have one.

 

[lark]

<a href=showthread.php?s=&postid=12396543#post12396543 target=_blank>Originally posted</a> by kenargo
A ground probe placed in a tank will complete the electrical circuit; it's like touching hot and ground at the same time except in the water the current flows between the faulty device the the ground probe. Without the probe there is no circuit.

Why is completing the circuit bad? With a properly functioning GFCI, it's good. It will divert to ground some current away from neutral in the GFCI and thus will trip your GFCI.

If you have current in the tank that is finding its way back to the GFCI, but is not being diverted via a ground probe, it's in the tank. YOU become the ground probe when you put your hand in. Wouldn't you rather that the ground probe trip your GFCI than you do?

It seems the circumstances where this could happen and not trip the GFCI are not that common, to be sure. But I thought the example in that article was a good one. You have one powerhead with a bare hot wire in the tank and a powerhead with a bare neutral across the tank. The current works its way through your tank from one to the other. You don't get a GFCI trip, because the circuit is being completed -- through your tank unfortunately. You stick your hand in. Now the hot current does not make it to the bare neutral but instead makes it to ground. Through the path of least resistance. You. A ground probe would have tripped the GFCI and would have alerted you to your bad powerheads.

The conclusion of Gerry's article is that a grounded tank is a closer approximation of nature than an ungrounded one, notwithstanding induced voltage and current -- unless I'm reading it wrong. That takes away the only objection that I've seen to using a ground probe, which means there is one reason to use one and none not to.

Here's the fundamental question: Assume a properly functioning GFCI. Now, give a single example where installing a ground probe makes the tank less safe.

 

[Deleted member 143833]

You have one powerhead with a bare hot wire in the tank and a powerhead with a bare neutral across the tank

If this happened then the GFI or circuit breaker would most likely trip. A direct short between hot and neutral would more than likely draw enough current to trip the breaker. It is also a very unlikely scenario but if it did happen, and the GFI/breaker didn't trip then you would smell and hear it so you wouldn't be sticking your hands into the water.

YOU become the ground probe when you put your hand in

Yes, you would, but it is this condition that a GFI is made for; it will trip before you feel the current because even though you make the circuit the GFI trips before the current through your body reaches a harmful point, actually it is so small you don't even feel it.

Assume a properly functioning GFCI. Now, give a single example where installing a ground probe makes the tank less safe

Safe for you or fish?

GFI doesn't trip at very small currents and most of the current in a properly running tank is induced (lights, pumps, etc). A ground probe in this case sinks this small current. Fish nibbles algae off probe, fish now part of the circuit, fish dies ??? You, the human would not likely be able to detect this small current so to you it is like it isn't there.

The conclusion of Gerry's article is that a grounded tank is a closer approximation of nature than an ungrounded one, notwithstanding induced voltage and current

Not diminishing what Gerry is saying, because it is a good article but I don't feel that you can take a limited amount of water (a tank), a single point of ground reference (grounding probe) and expand it to mean ocean and the vast ground plane the ocean contains (bottom). The ocean is grounded, yes but an open electric wire dropped into the ocean is very localized and quickly dispersed (either through ground/sand or distance). If you want to create the ocean equivalent of a ground then you would need to place a metal plate under your sand and ground it through a resistor (because ground it not ground all around). The ocean is also full of induced electrical currents, just on a larger scale.

 

[lark]

<a href=showthread.php?s=&postid=12397158#post12397158 target=_blank>Originally posted</a> by kenargo
If this happened then the GFI or circuit breaker would most likely trip. A direct short between hot and neutral would more than likely draw enough current to trip the breaker. It is also a very unlikely scenario but if it did happen, and the GFI/breaker didn't trip then you would smell and hear it so you wouldn't be sticking your hands into the water.



Yes, you would, but it is this condition that a GFI is made for; it will trip before you feel the current because even though you make the circuit the GFI trips before the current through your body reaches a harmful point, actually it is so small you don't even feel it.

I think the scenario being posited (again -- this comes from the grounding probe article posted in this thread, if you click on the link within that link) is that the current is travelling between hot on one device, and neutral on ANOTHER device, and no current (or less than 5 mA) is being diverted. If both devices are plugged into the same GFI, you would not get a trip -- the current would, however, be travelling through the water not the devices. The ground wire, in this scenario, brings the current to ground.

 

[Deleted member 143833]

It doesn't matter where the current goes from/to, if there where 1 hot and 1 neutral, both open to the water there would be a large current draw and I would still expect the breaker to trip.

The GFI (could) trip depending on whether or not the offending devices had a ground (3 wire plug) and how that wire was connected (and if it was exposed or not).

I still don't see this as a likely scenario; to have that kind of short.
but 'if neither tripped (for discussion sake) I would think you would hear and/or smell the short circuit. However, even if nothing tripped, and you touched the water that would trip the GFI immediately so still, no harm to human.

If you feel better you can add a ground probe, but if you do add ground probes remember to add them in all water sources; 1 in each tank, 1 in each sump, etc.

 

[mixed_reefer]

Heres a good read on probes.

http://reefcentral.com/forums/showthread.php?s=&threadid=1333989