_shorty_
New member
Do you power through GFCI circuit? I'm surprised this wouldn't trip your breaker/circuit.
Stray voltage?
- Thread starter MHG
- Start date
Do you power through GFCI circuit? I'm surprised this wouldn't trip your breaker/circuit.
mr.maroonsalty
New member
The question used to never be about electrocuting one's self; it was about protecting the animals. Use of a gfci is reefkeeping 101! The question was about stray voltage vs direct voltage. I don't know much about either.
How well will an AFCI protect our homes from an equipment overheating and starting a fire?
jtrasap
Elite Member
I ran my tanks for quite some time without them but for about the past five years or so I now have GFCI's on all of them.
jtrasap
Elite Member
An AFCI will not necessarily prevent a fire from overheating equipment but it can protect against fire caused by an electrical arc.
dkeller_nc
New member
Correct, Assuming that the grounding probe is truly grounded all the way back to a copper-sheathed grounding rod attached to your service entrance, or in an older house, the cold water bond.
However, if there is a problem back to one of these ground bonds, and you've drastically lowered your resistance by standing in a puddle of saltwater while working on your tank, and you have a device with a direct short, you're going to get a shock anyway.
This, is, by the way totally my risk calculation - decide for yourself:
I do not run a ground probe on any of my tanks (up to a count of 4 now - don't ask
), nor do I run any of the electrical power on GFCI or Arc Fault protection, whether by installed breaker box GFCI, electrical outlet GFCI, or power strip GFCI.This is why: I do not want my livestock killed by a malfunctioning heater/powerhead (that would be in the case of a grounding probe - mucho current running through the water, and probably through the animals). I do not want my livestock killed by the very common nuisance trips associated with GFCI and "normal" voltage surges on my line.
This is my risk calculation: I do not put my hands in a tank barefoot; all tanks are located on a dry wooden floor, and if I spill water during routine maintenance, I stop what I'm doing and clean it up.
Approximately speaking, the resistance of the human body is about 50,000 ohms. Having the requirement that the grounded circuit path go through dry rubber tennis shoes increases that value several-fold again.
It is therefore really unlikely that a normal person, in the situations described above, will be substantially harmed by a nuisance shock from a saltwater tank. It's certainly possible (and it's happened to me several times), and it's unpleasant.
But relative to the dangers present in everyday life, the probability of being seriously harmed is vanishingly small. If this were not the case, you would see far more newspaper/news station stories about so-and-so being electrocuted while working on his saltwater fish tank. There is only one documented case of this worldwide in the last 10 years that I have been able to find.
Contrast this with the number of traffic accidents specifically attributable to driving while texting last year in the US - 200,000. Or of getting food poisoning from Salmonella, Listeria or STEC (shiga-toxin producing e. coli) - approximately 1,500,000 cases per year in the US.
JiveWalker
New member
I'm still thinking you might be reading induced voltage. You could also have a bad ground, IF you are running submerged equipment that is grounded. Check for corrosion at the ground prong and receptacle. If you are not running any grounded equipment and don't have a ground probe, your animals should not be experiencing shock, some sort of neurological interference maybe, but not shock without a path to ground.
Are all cords entering the water at one location? Try separating and see if the reading changes.
Are all cords entering the water at one location? Try separating and see if the reading changes.
mr.maroonsalty
New member
I learned the hard way years ago about a tripped gfci; after that whenever I left for a few days I ran a cord from a non protected recepticle and plugged in a key power strip. My current build has the insurance of two circuits, I also run my external pump to a "black cover" recepticle wired before my gfci. Good circulation will keep the tank alive if not happy for quite a few days.
I often wonder when people say they were shocked by their tank if they really know what being hit by electricity feels like.
I often wonder when people say they were shocked by their tank if they really know what being hit by electricity feels like.
My main DT runs on two gfi outlets... Two years with out a trip.... My safety is worth more than my livestock...
My frag tank is now on a gfi with a probe and all voltage is gone.
My stray current was in the micro amps wich is what I would expect from stray voltage...
For what it is worth, a short = your breaker tripping or your tank going boom... Do not confuse stray voltage and a short...
My frag tank is now on a gfi with a probe and all voltage is gone.
My stray current was in the micro amps wich is what I would expect from stray voltage...
For what it is worth, a short = your breaker tripping or your tank going boom... Do not confuse stray voltage and a short...
An electrical short will not necessarily cause your breaker to trip and tank to go boom. Your breaker trips at either 15 or 20 amps of current. Depending on the nature of the equipment failure, you could very well see milli or micro amps from the short. A short could even result in a few amps and not trip the breaker. If you measure ANY current, then you have an electrical short. That current has to be coming from somewhere.
As for "stray voltage" without an electrical short, that's a myth. See my earlier post regarding the usage of a volt meter to measure voltage on a floating wire.
jtrasap
Elite Member
If you have stray voltage and no ground to the tank, you complete the short in the circuit if you're grounded and stick a part of your body in the water. If you have a ground probe connected to a tank and grounded, any equipment that is leaking voltage will effectively be shorted to ground and will not necessarily cause a breaker to trip.
dkeller_nc
New member
That isn't exactly correct, but it's very very close (probably close enough to ignore). Not only can a device directly produce voltage in a tank (i.e., a direct short), you can also have a (very small) induced voltage from spinning conductors/magnets in a conductive fluid. This throw-off is so mild, however, that it's really not worth attempting to measure.
Hmmmmm it's been a while since my formal education in electronics, but........a short is a direct path to ground and thus will draw current and that current will Increase instantly until maxes out to the ability of the shorted component or the breakers limit. Whichever gives first.... If a resistor shorts, then current seeks the path of least resistance to ground and will be pulled through it until the resister blows or other items in its path to ground....
So you are correct the tank may not blow or the breaker may not but something is gonna give of it is a short....
My point is don't confuse stray voltage with shorts. Shorts are the extreme in electrical malfunctions and there is no gray area...
So you are correct the tank may not blow or the breaker may not but something is gonna give of it is a short....
My point is don't confuse stray voltage with shorts. Shorts are the extreme in electrical malfunctions and there is no gray area...
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reefergeorge
New member
Induced voltage..
Can you please post a link showing the physics behind induction within a electrolytic fluid?
I'm quite familiar with induction in wires, how inductors work, the physics of electricity. I've had two years of engineering physics, and spent a significant amount of time studying electrical theory. I know of no physics that supports induction of voltage or current flow within an electrolytic fluid from magnetic fields.
Now, the physical movement of the pumps may temporarily tear off electrons, which would go free floating in the fluid. They'd soon recombine with other atoms that have lost electrons. Basically the same as static electricity, but within a conductive fluid. That effect would be incredibly small though, and very localized. Also, it would NEVER produce a current.
There is no induction of voltages in a fluid that i'm aware of, and in my searches I've found no physics supporting induction within a fluid as so many describe here on ReefCentral.
What I have already provided though is a link explaining how voltage meters are incapable of measuring voltage on a floating wire, due to the physics of how the meters read voltages. It appears to me that the random phantom voltages the meters provide in this situation has spawned this entire "stray voltage" phenomena that keeps being cited here on ReefCentral, but has no physics supporting it's existence.
That is a very electronics 101 description of a short. A more accurate description is that a short "allows a current to travel along an unintended path."
Further, the short itself will have a resistance. The resistance of the short will follow the following equation: r=pl/A, where A is the cross sectional area of the path, and p is the resistivity of the material, l is the length of the short.
If one were to hypothesize a micro fracture in the plastic housing of a water pump, the cross sectional area of the path into the conductors in the pump would be quite tiny. The resulting "wire" would be a very small path of the conductive saltwater. Because of having such a small cross surface area, it would have a very high resistance. The resulting voltage and current from such a small failure would not impact the functionality of the pump, however there would likely be a measurable current flow.
This would not be a catastrophic failure, it's quite possible that you could put your hand in the tank and not even know it. It's still a short. This is not theoretical, I have a skimmer pump which by visual inspection looks fine, but with no impeller in the pump, if I put it in salt water and measure current to ground there is a small current going to ground when I plug the pump in. I don't buy that it's "inducting current into the water" answer, it has a short. It's not 110v and high amperage either, so the short has a very high resistance.
JiveWalker
New member
Magnetohydrodynamics?
Very cool, hadn't seen that.
So, I can see how the original studies were looking for voltage and current potentials across a body of water generated by the earth's magnetic field impacting the flow of the water. It looks like the magnetic field will move the electrons similarly to how it happens in a wire.I don't see this phenomena could create a current flow out of the tank, or even something a voltage meter could measure more than a short distance from the pump (the magnetic effect would decrease exponentially, right?). It looks like the spinning magnets within the water would cause the electrons to flow around the pump within the water though. If you were to put in both probes of a meter around the pump, you might be able to measure a voltage and current flow localized around the pump. Does that sound accurate?
reefergeorge
New member
Now look into capacitive coupling.
I was aware of that, hadn't thought about it in this situation. Ok, so that would increase the range of the effect. Visualizing it I'd imagine ribbons of electron flow around the pumps from the magnetic fields, and then that flow would radiate out as the electrons interact. Sound like a fairly reasonable high level description?
Combined with the high impedance of the meter to measure for voltages (which is why it can't measure a floating wire), even though it's small this effect would certainly contribute to the meters inability to measure the voltage of the water.
I think randomness and chaos of the effect within the water away from the magnetic field wouldn't be sufficiently rhythmic to cause a volt meter to measure a current flow in AC mode though, and I don't see it creating a DC current.
It appears that with these effects, the results are still the same. Using a volt meter to measure for the voltage of a tank is useless, but measuring for current can still tell you whether or not you have a real short.
reefergeorge
New member
I'm not a believer in the GP theory, but always thought measuring the voltage drop across a resistor in series was the only way to be accurate.
My compromise last time was a GP on a light switch. Before you reach in the tank, ground it out in case something shorted out. Then turn it off so you aren't leaving a path to ground 24/7.
But I'm just an electrician. you guys are the ones that think it out.
My compromise last time was a GP on a light switch. Before you reach in the tank, ground it out in case something shorted out. Then turn it off so you aren't leaving a path to ground 24/7.
But I'm just an electrician. you guys are the ones that think it out.
