grounding probe

[Runner]

The unbalanced current required to trip a GFCI is very small -- 5 ma (milliamperes), I believe. It is possible to have a insulation break-down in an electrical component that allows a slight voltage increase on the surface of the insulation and yet still flow less than 5ma if there is a path to ground (like a ground probe). Not a big deal to us humans, but apparently sensitive corals and fish go nuts when exposed to this low-current. True, if this happens and you have a a GFCI and a ground probe, most of the time the GFCI will trip. Without the ground probe, the GFCI will trip when you put your hand in the tank. You'll get a little shock, but it shouldn't be damaging. Personally (speaking as an electrical engineer and a person in the reef hobby), I would never put a ground probe in a reef tank. Like (arguably) bio-balls, they belong in freshwater only where the critters aren't typically as sensitive. And never use a ground probe without a GFCI unless you really want to cook your tank -- a standard home breaker can flow 16 Amps of current for a long time before it trips.

P.S. I wish people wouldn't use the mythical term "stray-voltage" to describe low-grade insulation breakdown. The current is flowing exactly where it should go -- from the point of high potential to the point of low potential. More of an electrical "leak" than "stray voltage". Remove the ground probe and this path disappears and current won't flow (provided there is no other high-impedence path to ground). The tank will just rise to a steady-state voltage that doesn't harm anything (until you stick your hand in the tank, anyway).

 

[BeanAnimal]

Runner... you could not have said that much better.

Something that has been overlooked here by both sides.

A GFCI does not protect you if the fault happens to be "YOU" coming in contact with the hot and neutral. The GFCI sees "YOU" as the load and does not trip. In this scenario a ground probe will more than likely shunt this current to ground and trip the GFCI. I only offer this as a fact that can be used to help people decide which side of this debate they fall on. Certainly a rare scenario, but it does happen.

I happen to agree with RUNNER with resepect to the tank and it's critters. A Ground Prope poses many more problems than it solves. I think in most cases it cases more stress to the tank but can help to marginally lessen the physical danger to the tank owner.

This brings us to the whole question of "what should I do to work safely around a tank without a ground probe".

Firstly, don't dunk your hands in your system in bare feet on a concrete floor. Secondly, you may want to take a hard look at quality and condition of the elctrical devices plugged into your system. For example, old rios should be outlawed.. but tons of peoiple still use them.

Most quality pumps have 3 prong plugs, ensure that they are plugged into an outlet that has a working ground conductor. Some pump frames have a grounding screw that can be used as well.

With a little thought a small high impedance LED circuit could be built to "test" for dangerous potential in your tank. A simple "momentary" push button could be used to determine if "the water is safe".

Bean

 

[eddie c]

i have a ground probe that came with a system i bought but it's not the plug in the wall type it's just a probe with a wire attached to it, so how do i hook this up?, any info appreciated.

 

[phil5613]

Cool but confused?

Cool but confused?

I love when eletrical engineers (ala guys smarter then me) duke it out! As stated in a previous post I have used a grounding probe on a ro storage vat that was tied to a bad cold water ground. But that is the only time I have used one. I am putting together a 210 reef right now and am considering a probe. This post confuses me in the point that will it help or hurt the tank inhabitants? I have gone and run two 20 amp dedicated circuits with a a total of 16 GFCI protected outlets just to do this right. I have also seen live tests that show voltage in the tank with out anything powered except for the MH above the tank so I do believe in the stray voltage theory. My question being is there proof that probe hurts or helps the tank? I am a Techie with over 10 years in the telephony field including central office powering so I know it can be explained in theory how its supposed to work but is there any real life non EE proof out there?

 

[fishtk75]

IMO I would use a ground probe's and GFI.I have one in every tank because I had heaters go bad and put my hand in there with no GFI and Ground probe and ZZZZZZZZZZZZZZ
fizzy hair.
No more it only takes a second. For a the money be safe then sorry.
You can do what you want this one not ready to go 6 feet into ground let the electric go first.

 

[JC Pollman]

Perhaps part of the controversy here is, I believe, confusion on two possible problems:

1. Problems affecting us:
a. Catastrophic failure: if a seal breaks on a heater, and you put your hand in the tank - say, to feed the inhabitants - and you do not have a ground probe plugged into a GFCI, you are going to have a bad day.

b. If you have electrical mechanisms putting minor amounts of electricity into the water, you will not know about it if you have a grounding probe - which means you could be inviting trouble down the road.

2. The other problem is: how does the electricity affect the tank's inhabitants? There are plenty of comments, though I know of no scientific proof, that current in the tank can cause/encourage hole in the head/lateral line disease in tangs. With a ground probe in the tank, the electricity is flowing as you have a circuit, but with no grounding probe, the electrical potential just increases, yet most people recommend using the probe. Not sure I understand this reasoning.

 

[BeanAnimal]

JC pretty good summary.

In the end the aquarist has to decide if personal safety or possible livestack stress is more imporant. Ground propes and GFIs work together to increase safety, but at the same time allow current to flow through your reef and can cause a little (or in some cases deadly) stress to the system.

 

[Runner]

<a href=showthread.php?s=&postid=6982793#post6982793 target=_blank>Originally posted</a> by BeanAnimal
With a little thought a small high impedance LED circuit could be built to "test" for dangerous potential in your tank. A simple "momentary" push button could be used to determine if "the water is safe".

I really like that idea. I may have to give that a shot...

@phil5613: Voltage rise can be created in a tank by a nearby electrical field. The high voltage in a MH setup would be a good culprit. If the tank is isolated from ground, the voltage will drift. Also, mere water motion introduces a static charge in an ungrounded system. A ground probe always makes it safer for humans. Anecodotal evidence says it could be responsible for killing critters, though.

 

[wet reefer]

In the end the aquarist has to decide if personal safety or possible livestack stress is more imporant. Ground propes and GFIs work together to increase safety, but at the same time allow current to flow through your reef and can cause a little (or in some cases deadly) stress to the system.



That pretty much sums it up Bean.
It shouldnt be too hard to decide which is more important.
Too many people are ignoring what is causing the current flow. If a piece of equipment is leaking enough current to be a problem either with livestock or tripping a ground fault then it should not be used.