Weird issue w/ stray voltage... electrical whizzes I need ya!

[cr500_af]

I periodically check my tank for stray voltage, and have always gotten a reading no matter what. Since tonight I had an actual problem, I'll run it down:

Felt a tingle working on the tank when my hand touched to housing of a halide while also touching water, so I grabbed my meter. I had a reading of around 110v. I started unplugging things, and the only one that dropped the voltage was a heater. So far, so good; get rid of the heater.

The kicker is that I still show at least 30VAC in the tank! The exact reading wanders/varies a little, but is usually floating around that number. This is with NOTHING live that touches water in any way. The only thing left plugged in was my halides and canopy fans (and they do not contact any moisture at all). No pumps, heaters, skimmers, ATO... all unplugged.

Now, the shock went away with the faulty heater, but why in the world would you see a voltage reading in a tank with no electrical equipment plugged in??? This was verified with two different meters, BTW.

I should also mention that I have seen this in another member's tank also. Everything unplugged (no exeption) and still reads voltage.

 

[jdabs]

Must have an electric eel hiding in there! J/K Barry! It's late!! Hope you are able to figure this out!

 

[cr500_af]

No, Andy, the only thing in the water that was not disconnected was the temp probe from my RKL. I don't think those carry any current, do they? I can kill it and see.

 

[cr500_af]

Glass, and I'm checking the voltage in the sump, while I felt the shock in the DT.

 

[ichthyoid]

Barry, this will sound like some science experiment, but have been told I am good at breaking it into bite sized chunks.

The voltage from your light (usually the source as you will see) is superimposed onto the water of your tank. How does that happen?

In a nutshell, your lights operate at 60 herts (current changes direction that many times each second), and depending on the ballast design may operate at much higher frequency (thousands, to hundreds of thousands of hertz).

Next, anytime you have an alternating voltage (the light for example, but could</em> be some other device) separated from another conductor (tank water) by an insulator (air), then you have what is known as a capacitor. You may be familiar with these.

Voltages may 'superimpose themselves' (impress their potential, sort of like an object casts its shadow when illuminated) across the insulator gap to the other conductor (tank water). When this happens it is known as capacitive coupling and you can read the voltage.

A good depiction of a 'natural capacitor' may be illustrated during a lightning storm. Clouds generate huge voltages (I'm not going to explain that here for brevity) which can induce the opposite polarity voltage onto structures on the earth below them, such as buildings and trees. High speed cameras have shown the lightning bolts actually form from both objects. This happens in aquariums, but because it is AC, it happens more easily. Not to worry, the current, which is the part that can hurt you, is usually negligible.

 

[cr500_af]

Thanks for the lesson! However, the MH lamps (as well as the actinics) are out now (and I've unplugged them in my troubleshooting) and I still have 59-60 VAC in the tank. Every electrical item (pumps, skimmer, PHs) has a miniscule effect (dropping maybe 1-2 volts off the number) when I unplug it, but other than the bad heater, nothing has made a significant drop. I have literally unplugged every item one by one and the voltage remains. Anything that is wet has been unplugged, and I'm pretty sure that other than my RKL I've unplugged everything that isn't wet. I did remove the temp probe from the sump with no change.

I realize that trace amounts of voltage are normal but I feel pretty confident that sixty volts is not. :confused2:

 

[ichthyoid]

I don't doubt that everything is turned off. But you still have a charged conductor (wires?) somewhere close to the water in that tank (within inches), or your tank defies the laws of physics, I promise. From your prior posts I know you're a smart guy. Take a look. I bet you will find it/them. Then when you isolate and de-energize that source of electrical potential you should no longer measure any AC. Keep me posted, otherwise the cheese will slide off my cracker!-lol

 

[cr500_af]

Let's pretend I slept during EE101, and let me ask: by "de-energize the source of electrical potential", what method exactly would one use, if unplugging isn't enough?

 

[ichthyoid]

Yes that would do it.

So you are confident that you have no energized wires within say a foot of your tank, and still measure 60 VAC?

 

[cr500_af]

I have unplugged every item on the system one by one, including both Reefkeeper power modules. I haven't unplugged the DJ power strip itself, but I have unplugged each component from it. I am wondering if I have TWO culprits, and maybe should kill the entire system and plug each item in one at a time, rather then unplugging individually. But yes, I am getting 59-67 VAC depending, as my Grandmother would say, on "how I hold my mouth".

Stand by!

 

[ichthyoid]

I'm thinking there's gotta be a wall with a romex run next to the tank, or an appliance, wiring under the stand, something; but it has to be close. This stuff obeys the inverse square law, which means distance has to be inches!

 

[cr500_af]

ichthyoid;451846 wrote: I'm thinking there's gotta be a wall with a romex run next to the tank, or an appliance, wiring under the stand, something; but it has to be close. This stuff obeys the inverse square law, which means distance has to be inches!

I built the house (inlcuding the electrical)... the only thing in that wall is the Romex for the circuit that the tank is on (and BTW the only other thing plugged into that whole circuit currently is a clock radio; it is for the guest bedroom). There is also a doorbell transformer, but it is 8 feet down the wall and right up by the ceiling.

The panel is in the basement under the tank area, but not that close... probably 6-8 feet away plus the vertical distance. The service wire doesn't come from the direction that would run it under the stand.

 

[ichthyoid]

C=kA/d

c=capacitance
k=dielectric constant of air (this is fixed)
A=area of the conductor
d=distance separating the two conductors (from the tank)

so, it's either a REALLY big conductor, like a sheet of metal
or, it's a really small distance (from tank)
or some combination of both

 

[cr500_af]

I'm going back to Occam's Razor... a defective piece of equipment. I've just gotta isolate it/them. I'm going to disconnect the entire system and start from "darkness". Maybe working it from that direction will produce something.

 

[ichthyoid]

Can you kill the breaker? I believe your ground will be in tact as it does not go through the breaker, so using it for reference will still work.

Man this one has me twisted! I may have to run out to Dallas (right?) for a consultation/investigation.

 

[cr500_af]

Yes, the breaker is no sweat. It won't turn anything else off except the tank, doorbell and a clock. I'm going to figure this out before I either go to bed or leave for work, depending on how tough it is!

 

[ichthyoid]

Pease keep me posted. I need to go get some shut eye, so I'm not a total zombie tomorrow. Wow! This is gonna be one of those where we both go..."oh, yeah, of course"... I'll bet-lol.

 

[cr500_af]

Well, no answers there, but the problem is no more (at least for now). Killed the whole system, and reconnected one item at a time waiting for the voltage spike... and it never came. All is up and running now with 2V measured in the tank (which I'd say is normal). I'm going to be checking this thing nonstop in case the problem reappears.

I hate not knowing what was wrong, and at least for now I can't duplicate the problem.
Thanks a ton for the help!

 

[ichthyoid]

You bet, any time. I'm the same way, can't stand not finding the smoking gun. I'm a 'root cause' guy too!

 

[johnr2604]

Could it be that saltwater contains ions in solution and your meter probe is metal?