DIY - How to test for Stray Voltage in your Aquarium

[DocP]

Video showing how to test for stray voltage in your tank from bad or malfunctioning equipment. Any questions feel free to ask.

[trinidiver]

interesting and informative info

[rovster]

Cool vid. How much stray voltage is considered acceptable and will not harm livestock? Or is any stray voltage bad? Thanks!

[kcress]

Don't worry about it until it gets over 50V. Anything under 50V is just capacitively coupled AC. Consider it a "signal" not "power" until 50V.

[trinidiver]

Will have to check mine when i get home

[uncleof6]

Originally Posted by rovster

Cool vid. How much stray voltage is considered acceptable and will not harm livestock? Or is any stray voltage bad? Thanks!

Stray voltage of any magnitude is not harmful. Voltage does nothing. It is current that does something, and is what can be potentially dangerous. Without a path to ground, there is no current flow.

The voltage in the tank, can be read with the meter, because a current flows through the meter to ground, due to the voltage potential in the tank. Remove the grounded test probe, you get no reading = no current flow. Current does the work, not the voltage.

Anything under 40VAC, is considered "low voltage," as in most cases the current flow caused by this potential, would be harmless. Getting above 50VAC, as kcress indicates is "high voltage" and the potential for injury or death is present, if that voltage is given a path to ground.

Saltwater, due to its ionic nature, will always show some potential (voltage) between the water and ground. The potential may be too small to measure, or you may read 12VAC, or so. Also, inductive loads (pumps) can impress a voltage in the water--due to the magnetic fields, yet not be damaged or malfunctioning. However, if you are reading something above 40VAC, it is cause for further investigation.

[DocP]

Glad you all found it helpful. I won't go into how much is to much since kcr and uncle already covered it.

[rovster]

Originally Posted by uncleof6

Stray voltage of any magnitude is not harmful. Voltage does nothing. It is current that does something, and is what can be potentially dangerous. Without a path to ground, there is no current flow.

The voltage in the tank, can be read with the meter, because a current flows through the meter to ground, due to the voltage potential in the tank. Remove the grounded test probe, you get no reading = no current flow. Current does the work, not the voltage.

Anything under 40VAC, is considered "low voltage," as in most cases the current flow caused by this potential, would be harmless. Getting above 50VAC, as kcress indicates is "high voltage" and the potential for injury or death is present, if that voltage is given a path to ground.

Saltwater, due to its ionic nature, will always show some potential (voltage) between the water and ground. The potential may be too small to measure, or you may read 12VAC, or so. Also, inductive loads (pumps) can impress a voltage in the water--due to the magnetic fields, yet not be damaged or malfunctioning. However, if you are reading something above 40VAC, it is cause for further investigation.

Good info. Should we and can we measure current then? What are all these posts of stray voltage causing HLLE? Coincidence is, I have a Blue Tang right now in QT/HT that looks like its suffering from HLLE. Its acting normal, eating normal, but looks all beat up (erosions on body, and fins tore the "f" up). I tested for stray voltage and I didn't get any. I'm now counting on it being a nutritional issue, which I am working on. Friggin fish, I love the damn thing but I wish it could just tell me what's wrong and what to do, LOL!

[merlangshane]

I'm a bit confused because my tank is increasing in voltage when I use a grounding probe.

With all my equipment plugged in, my volt meter shows 15-17v but when I plug in my probe it jumps up to 26v. None of the lfs or electricians can explain to me why this would happen, and I think this is why I have been unable to keep any new fish in the tank.

[uncleof6]

Remove the grounding probe, they are the work of the devil. 15 - 17 volts in the tank, is of no concern, and would be quite normal considering the salt water is an electrolyte, and there is an abundance of inductive loads. The grounding probe creates a current path, that should not exist. Volts are not harmful, current (Amps) is.

[sleepydoc]

Uncleof6 is correct that voltage isn't the problem, current is, specifically current going through an organism. However the problem is that voltage drives current, and you don't know how much current a voltage can drive until you complete the circuit. Volt meters are designed to have extremely low current draw, so they can measure the voltage, but they won't tell you how much current will flow.

If the voltage is an induced voltage from an electric motor, it won't be able to drive much current, but if it is from a crack in a wire you could get a lot more. Both may read the same on the volt meter, the difference is the impedance of the path to ground.

The only way I can explain merlangshane's findings is that because of the gounding probe, there was an increased current, which then increased the voltage in the tank because the water, although a good conductor, has a finite resistance.

Personally, think Uncleof6 is right - get rid of the gounding probe and make sure you're on a properly functioning GFI outlet for all your equipment.

[jcolley]

Bumping an old thread, I know...

But why the desire to remove the ground probe. IMO, it exists as a safety precaution for the person. Difference in potential is difference in potential. It doesn't matter if it's ground to any other place with a lower potential than whatever is currently in the water. If a path exists, current will flow. Providing a ground probe in the water gives a safe(r) path for current to flow than through a body part.

Using GFCI receptacles, the ground probe has a good chance to trip the GFCI if any voltage in the body of water is present a result of insulation degradation since the GFCI monitors a difference between current flow on the "hot" and "neutral" phase, assuming any mismatch is leaving via ground.

The ground probe provides that exact path and the GFCI tripping may be incovenient, but I would rather chase a ground than go the ER (again) for an EKG.

The presence of the ground probe does not increase the danger to a person. The current flow through a ground probe (assuming a pre-existing fault and presence of non-induced or impressed voltage) exists whether a hand goes in the water or not. The addition of the hand to the circuit does not alter the resistance of the ground probe node of the resistance network, so according to Kirchoff's Current Law, does not alter the current. While the hand does add an additional resistance node in parallel, the current flow through that node (hand/arm/body) will be entirely dependant upon the body's a)internal resistance b) resistance of hand/water interface and c) interface of other part of body to ground.

The additional benefit of the ground probe would be that it acts identical to a shorting probe and essentially "grounds" the water in the immediate vicinity of the probe. This is right in line with safety protocols in place by OSHA for working on high energy systems such as substations, etc. You will always see a shorting probe placed on a conductor after the initial entry and voltage verifications are performed as a means to protect the worker in process.

I personally have two grounding probes on opposite ends of my tank since there is a resistance (therefore difference in potential) from one end to the other in seawater. I have had my GFCIs trip and was annoyed at the time, but thankful later when I figured out a Maxi-jet feeding my GFO reactor had a failed housing.

I'm curious if anyone has measured the "stray" voltage in a tank with an analog meter. In my field, we routinely enter high voltage systems and encounter induced voltages". Lessons learned from a a worker getting shocked by an "induced voltage" revealed that the initial voltage verification was performed and the induced voltage was noted at the time. However, upon further investigation, the workers did not follow the procedure to *verify* the noted voltage was induced by using an analog meter which will read 0V.

Digital meters are quite useful, but have their limitations, many of which are a result of the auto-ranging resistance networks necessary to feed the the internal A-D converter without under/overdriving its amplifer circuit.

Not trying to stir any pots or step on any toes, but I think a healthy discussion is beneficial when there are so many conflicting points of view.

[uncleof6]

Every six months to a year, someone dredges up this tired old subject. There have been hundreds of healthy discussion on this topic, they are always circular, and never go anywhere. The bottom line is however, if you feel that a continuous electrical current flow through the tank is a good thing, if you feel that subjecting the life in your tank to a continuous electrical current is a good thing, and if you feel turning your aqaurium water into a ground plane, a ground plane that should not exist, with a myriad of inductive loads around, is a good thing, then no amount of discussion (even with electrical engineers that really do understand the conditions) is going to sway anyone from the false sense of security that uninformed fellow reefers, marketing strategies, and adding 2 + 2 and coming up with 3, have imparted on them. Do some research with the NFPA, and Arson.org. You will find that fatalities/serious injury/loss associated with aquariums fall into the category of homicide/arson, rather than associated with the salt water directly, involving the misuse of multi-outlet devices and the rats nest of electrical cords UNDER the tank.

[jcolley]

Wow.

My apologies, I'll leave it alone.

[firebirdude]

Just tested mine. 37-47VAC depending if the heaters are on. Guess that's acceptable. Two powerheads, two 250W heaters, 3 ReefKeeper probes, and return pump.

[sfsuphysics]

Originally Posted by jcolley

Bumping an old thread, I know...

But why the desire to remove the ground probe. IMO, it exists as a safety precaution for the person.

You could always do like computer techs do, you put on a grounding "strap" when working on computers, toss in your grounding probe when you're going to work on the aquarium, pull it out when you're done.

[uncleof6]

Originally Posted by firebirdude

Just tested mine. 37-47VAC depending if the heaters are on. Guess that's acceptable. Two powerheads, two 250W heaters, 3 ReefKeeper probes, and return pump.

Ummmm, if your voltage reading is going up when the heaters are on, and goes down when the heaters are off. I think you had best carefully examine your heaters. Heaters are not inductive loads, rather resistive, and should not be impressing a voltage on the tank...

[MikesReef83]

If you use two heaters would it be smart to have one on its on gfci or on the same?

[MikesReef83]

Originally Posted by MikesReef83

If you use two heaters would it be smart to have one on its own gfci or on the same?

[MikesReef83]

Sorry double post

[uncleof6]

It really does not make any difference...

[beertech]

I was recently messing around with my leds above the tank. I unplugged the rca jack from one of the 9v wall warts and didnt notice that it had fallen into the tank.
I noticed my clam opening and closing, and assumed it was reacting to the change in light. Anyway, it was in the tank about 10 min total. After the incident i lost all of my xenia. Every bit of it melted away within the next 24 hrs. No other coral losses and no fish losses.
This leads me to assume that certain species maybe more sensitive to electrical current just as some are sensitive to certain water params.

[tufkab]

Originally Posted by beertech

I was recently messing around with my leds above the tank. I unplugged the rca jack from one of the 9v wall warts and didnt notice that it had fallen into the tank.

I noticed my clam opening and closing, and assumed it was reacting to the change in light. Anyway, it was in the tank about 10 min total. After the incident i lost all of my xenia. Every bit of it melted away within the next 24 hrs. No other coral losses and no fish losses.

This leads me to assume that certain species maybe more sensitive to electrical current just as some are sensitive to certain water params.

Recently I got home from work and took a shower; the next day I woke up with a cold. This leads me assume that taking a shower after work causes the common cold.

That sounds pretty ridiculous doesn't it ? But it's the exact same thing as your example. Correlation is NOT causation. What you said happened simply can not cause what you are describing.

Electricity doesn't work that way. If you had put a positive lead on one end of the tank and a negative on the other end, then MAYBE you could look at that as a cause. But even then, 9v at maybe 500ma would do nothing. Even if you were putting through much higher voltages and current, you also have to think about conductivity; if the water is more conductive than coral tissue, current will flow around, rather than through.

[beertech]

I think its a pretty big coincidence...mature tank with full large colonies of coral including xenia. Nothing else happened to the tank at that time, no additives, no water changes, heaters both intact. Temp, ph, alk, salinity all remained constant. I really cant think of.anything that could cause all of the xenia to literally melt and dissolve within a 24 hour period. Anyone willing to test this? Maybe ill set up a small tank with a sample of xenia and see what happens. Ill post when done....

[uncleof6]

Originally Posted by beertech

I think its a pretty big coincidence...mature tank with full large colonies of coral including xenia. Nothing else happened to the tank at that time, no additives, no water changes, heaters both intact. Temp, ph, alk, salinity all remained constant. I really cant think of.anything that could cause all of the xenia to literally melt and dissolve within a 24 hour period. Anyone willing to test this? Maybe ill set up a small tank with a sample of xenia and see what happens. Ill post when done....

Ok, probably a coincidence. You dropped an "rca" jack coming from a wall wart, into the tank. The wall wart produces 9 volts. (it was probably a little less than that, as wall warts are not the most efficient devices around.)

The voltages we are discussing are between 12 and 40 volts. ( 9 volts is close enough.) The problem is, we are discussing VAC (volts alternating current.) What comes out of the wall wart is VDC (volts direct current.)

DC is not what the concern here is, it is AC. With the rca connector from the wall wart, the center post is the +, and the "outside" is the ground. Where the dc current went, if it went anywhere at all, was from the center post, cross the short distance to the ground portion of the connector, and the only reason the wall wart did not burn up, is the resistance of the salt water.... the current did not go "running around" in your tank.

Even with faults in ac motors, (most often they are high resistance line cord faults, because they often don't use the best cords for the job...) the current flow will remain local to the faulty pump/cord (path of least resistance is to the ground of the pump, or the neutral, if either path exists.) The current would remain local to the pump, or it can impress a voltage in the tank, if a path to ground is not present.