Grounding probe or No grounding probe

[Randy Holmes-Farley]

FWIW, induced voltage in seawater won't necessarily be eliminated by a ground probe. By its very nature, induced voltage varies with location in the tank, and may have different signs at different locations. What it may eliminate is an overall different net charge to the tank than the ground.

In an induced charge scenario, a ground probe will simply reduce the induced voltage in the very near vicinity of the probe, but it does not impact the primary electric field away from the probe, and thus also does not impact the mirror potential that forms in the seawater.

Wikipedia discusses induced charge in conductors (like seawater is in our case) here, and the fact that the conductor in the example is grounded makes no difference. It still gets a mirror charge:

http://en.wikipedia.org/wiki/Method_of_image_charges

from it:



The field of a positive charge above a flat conducting surface, found by the method of images.

 

[Dcmatranga]

Very interesting article - I learned a few additional things. Prior to this, I didn't think that the location of the probe/equipment was relevant, but interestingly enough it sounds like it is and makes sense due to the fields. The only thing I may add, and this may only be unique to my situation - but all of my equipment, minus the 2 MP40's (and we know how those work lol) is in my sump as well as the grounding probe - luckily (for me), when I added the ground probe I watched the reading on my multimeter drop to zero in both my 100g display and 30g sump.

 

[Randy Holmes-Farley]

Very interesting article - I learned a few additional things. Prior to this, I didn't think that the location of the probe/equipment was relevant, but interestingly enough it sounds like it is and makes sense due to the fields. The only thing I may add, and this may only be unique to my situation - but all of my equipment, minus the 2 MP40's (and we know how those work lol) is in my sump as well as the grounding probe - luckily (for me), when I added the ground probe I watched the reading on my multimeter drop to zero in both my 100g display and 30g sump.

That's good to know. That sort of induced voltage must be generated some way other than mirror charges, but I'm not sure how aside possibly from electrostatics (such as comes from friction, like a balloon rubbed on your head).

 

[Dcmatranga]

That's good to know. That sort of induced voltage must be generated some way other than mirror charges, but I'm not sure how aside possibly from electrostatics (such as comes from friction, like a balloon rubbed on your head).

I was thinking more along the lines of electromagnetic induction - similar to the principle behind the MP40's, mostly found in motors and devices that use resistance to generate energy. I could be way off target...

 

[Randy Holmes-Farley]

I was thinking more along the lines of electromagnetic induction - similar to the principle behind the MP40's, mostly found in motors and devices that use resistance to generate energy. I could be way off target...

That would be the mirror image induction then.

 

[christojean]

Chargers

That would be the mirror image induction then.

I am an electrical engineer so my comment may not matter! However, voltage is "potential" when you are measuring voltage it is the difference between some medium and a reference point. We as humans have a voltage. Voltage is the same as a weight sitting on a table. If dropped from the table that weight moves and if stopped half way to the floor, it now has half the potential (keep in mind the weight can only do damage when its potential is changing). With voltage it is the same (were the change in voltage is current). Voltage can build in many ways in a tank. Water is moving and many plastic parts are also moving in the water. Plastic holds potential until a path is available to release it. Conductors shed potential and are why we use them to move potential. We have plastic pipes and tubes with water moving through them... as this happens positive charges or negative charges are attracted and will build on these plastic surfaces or any dielectric in our systems. When we measure between "ground" and our tank we see this built up potential. A grounding probe is a good way to remove these small amounts of voltage. If a device is shorted and releasing voltage, but not enough to trip a breaker( or a faulty breaker), you will have a larger power bill and current in your system which could be hazardous. I really don't see the harm with having a voltage in a floating system. That being said I have a grounding probe on my tank, but have seen no difference than when I did not!

 

[Dcmatranga]

I am an electrical engineer so my comment may not matter! However, voltage is "potential" when you are measuring voltage it is the difference between some medium and a reference point. We as humans have a voltage. Voltage is the same as a weight sitting on a table. If dropped from the table that weight moves and if stopped half way to the floor, it now has half the potential (keep in mind the weight can only do damage when its potential is changing). With voltage it is the same (were the change in voltage is current). Voltage can build in many ways in a tank. Water is moving and many plastic parts are also moving in the water. Plastic holds potential until a path is available to release it. Conductors shed potential and are why we use them to move potential. We have plastic pipes and tubes with water moving through them... as this happens positive charges or negative charges are attracted and will build on these plastic surfaces or any dielectric in our systems. When we measure between "ground" and our tank we see this built up potential. A grounding probe is a good way to remove these small amounts of voltage. If a device is shorted and releasing voltage, but not enough to trip a breaker( or a faulty breaker), you will have a larger power bill and current in your system which could be hazardous. I really don't see the harm with having a voltage in a floating system. That being said I have a grounding probe on my tank, but have seen no difference than when I did not!

Well said - now, I agree with the damaged device and current in the system - one question I have that is a bit above my head, would the medium the current used to find path to ground be conductive enough to trip the breaker? If not, wouldn't it be the GFCI's job to trip that said circuit since it found a path of less resistance that would be measurable between 4-6mA to trip the GFCI? You had mentioned you didn't see a difference in voltage before or after the ground probe - below is a quick before and after I just took and wanted to share from my own experience. First reading (ground probe removed) on the left was taken with one lead in my sump and one lead on the yoke of the receptacle ensuring ground. The reading on the right (ground probe in) was taken with one lead in the sump and one lead on the tail of the ground probe which has a ring terminal that is attached to the center of the wall plate which attaches to the yoke of the receptacle.

 

[christojean]

I am not saying there was no voltage difference but that I saw no changes in my livestock or corals. As far as if the GFCI would work, I would say maybe! It depends on the short or leak. If the circuit is shorted then it could draw equally from both sides, but the breaker should work at that point. It is very hard to say as many things could happen! In my opinion, the use of a ground plug is up to the user, and if there is a large leak the breaker should step in... But to be safe, always unplug everything before working in the tank!

 

[Pirates.Reef]

I placed one in my sump and display after I got shocked by a Rio skimmer pump because it can't hurt to have it as a safety.

 

[Randy Holmes-Farley]

Voltage can build in many ways in a tank. Water is moving and many plastic parts are also moving in the water. Plastic holds potential until a path is available to release it. Conductors shed potential and are why we use them to move potential. We have plastic pipes and tubes with water moving through them... as this happens positive charges or negative charges are attracted and will build on these plastic surfaces or any dielectric in our systems. When we measure between "ground" and our tank we see this built up potential. A grounding probe is a good way to remove these small amounts of voltage.

Thanks. That's the frictional sort of electric potential I was referring to earlier.

 

[NeveSSL]

I've heard the term "ac coupling" thrown around. How would that differ from the inductive voltage discussed here?

Brandon

 

[sucker]

This thread is interesting to me - I'm an electrician by trade and electrical theory has always been of interest to me. Ground probes and safety are kind of tricky words to use in the same sentence. From my experience - a ground probe should only be used to correct an induced stray voltage issue (fairly common). While induced voltage is measurable - it is not stray voltage from damaged equipment, or voltage leakage - which is measurable as well. That said, if you have induced stray voltage running through your tank, and don't have a ground probe it is likely to stress your livestock as it did mine. I troubleshot from a-z every which way you can think of to identify the root of this problem and come up with a solution for my situation.

agreed

 

[sucker]

Updating...
Just received the ground probe today, it's $11.59 on Amazon

Before: 34.9V, 0.026mA
After installed the probe: 0V, 0mA. And gfci didn't trip

Will keep the voltmeter around to monitor the voltage before I put my hand into the tank

 

[Windy]

I don't see any claim about a safety device on the package. I wonder why?

 

[redfishbluefish]

I don't see any claim about a safety device on the package. I wonder why?

You don't want to make a claim for which you could then be sued.

 

[lionfish5740]

Nice informative thread! My random thoughts...

I've always been told that it's the amp that is dangerous to people and not the voltage, but I think that would only hold true to a certain point. With the fact that electricity takes the least restricted path, wouldn't it keep us from getting shocked?
If I'm not mistaken it's a small amount of current required to be harmful, not sure the value though.
But there is a relationship between all the electrical values if I remember correct from physics class. Would need to know the resistance in the body and the amount of amps that is dangerous to us to find the voltage value that could cause trouble. Surely google could give a commonly accepted value. LOL
I would believe that people with certain cardiac arrhythmias would be most susceptible to serious problems of stray electrical coursing through them.

My thoughts for the probe haven't been mentioned yet. Wouldn't it be better to have some audible alarm on the probe so that it alerts you to an exposed current in the tank? Otherwise, like mentioned before, the electric bill could rise significantly. Then more importantly, you also wouldn't be aware that you have an issue with your equipment and possible danger if your ground probe failed for some reason; like you accidentally tugged the wire and lifted it out of the water.

My other thought for the probe would be that it would act as an electron sink for certain bacteria and provide another (permanent?) electron acceptor, which would allow them to stay aerobic and thus more efficient with the redox chemistry of our tanks. Respiration is the most efficient method for facultative bacteria. But I'm not aware of the bacterial species in our tanks and there's likely differences tank to tank but any buildup of biofilm around the probe would possibly be beneficial, assuming those are the beneficial bacteria utilizing it in our tanks. The idea came to me from noticing a biofilm that seems to regenerate around an electrical wire in my sump with minimal water flow; could be a coincidence though as the wire isn't exposed.
I wonder, would somebody have the testing ability and time to test such a biofilm on a probe for species and see if this hypothesis would be beneficial?? Maybe it would only be a tiny amount but to some people that amount could be the difference in the tank succeeding or not.

 

[sucker]

I don't see any claim about a safety device on the package. I wonder why?

 

[Dcmatranga]

I've always been told that it's the amp that is dangerous to people and not the voltage, but I think that would only hold true to a certain point. With the fact that electricity takes the least restricted path, wouldn't it keep us from getting shocked? If I'm not mistaken it's a small amount of current required to be harmful, not sure the value though.

That is correct, amperage is what kills - and takes very little to do damage. https://www.osha.gov/SLTC/etools/construction/electrical_incidents/eleccurrent.html Is a good chart to refer to. You will see at the 5mA mark it says may lead to serious injuries. I believe that is why GFCI's have a trip level of 4mA to 6mA.

My thoughts for the probe haven't been mentioned yet. Wouldn't it be better to have some audible alarm on the probe so that it alerts you to an exposed current in the tank? Otherwise, like mentioned before, the electric bill could rise significantly. Then more importantly, you also wouldn't be aware that you have an issue with your equipment and possible danger if your ground probe failed for some reason; like you accidentally tugged the wire and lifted it out of the water.

An audible alarm would be good to detect induced voltage - but any current flowing would mean it found a path of least resistance to ground (most likely not your neutral) and was in direct contact with exposed "potential" or voltage (damaged equipment) and should trip the GFCI by measuring the difference between the hot and the neutral. I've always looked at the amperage on my Apex but will look at it more closely for a change in trend, hopefully can help foresee a piece of damaged equipment and can shut it right down.

 

[Randy Holmes-Farley]

I've heard the term "ac coupling" thrown around. How would that differ from the inductive voltage discussed here?

Brandon

That sounds exactly like induction.

Bear in mind, however, that a simple conductor like seawater won't respond anything like a magnet does in a moving electromagnetic field (as in a motor).

 

[NeveSSL]

Thanks, Randy.

Brandon